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  • Nov 27th 2012
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Best Measuring Instrument of All Time

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    1
    S meter

    S meter

    An S meter (signal strength meter) is an indicator often provided on communications receivers, such as amateur radio receivers or shortwave broadcast receivers. The scale markings are derived from a subjective system of reporting signal strength from S1 to S9 as part of the RST code. The term S unit can be used to refer to the amount of signal strength required to move an S meter indication from one marking to the next. The International Amateur Radio Union (IARU) Region 1 agreed on a technical recommendation for S Meter calibration for HF and VHF/UHF transceivers in 1981. IARU Region 1 Technical Recommendation R.1 defines S9 for the HF bands to be a receiver input power of -73 dBm. This is a level of 50 microvolts at the receiver's antenna input assuming the input impedance of the receiver is 50 ohms. For VHF bands the recommendation defines S9 to be a receiver input power of -93 dBm. This is the equivalent of 5 microvolts in 50 ohms. The recommendation defines a difference of one S-unit corresponds to a difference of 6 decibels (dB), equivalent to a voltage ratio of two, or power ratio of four. Signals stronger than S9 are given with an additional dB rating, thus "S9 + 20dB", or,
    8.38
    8 votes
    2
    Anemometer

    Anemometer

    • Dimension measured: Wind speed
    An anemometer is a device for measuring wind speed, and is a common weather station instrument. The term is derived from the Greek word anemos, meaning wind, and is used to describe any airspeed measurement instrument used in meteorology or aerodynamics. The first known description of an anemometer was given by Leon Battista Alberti around 1450. Anemometers can be divided into two classes: those that measure the wind's speed, and those that measure the wind's pressure; but as there is a close connection between the pressure and the speed, an anemometer designed for one will give information about both. A simple type of anemometer, invented (1846) by Dr. John Thomas Romney Robinson, of Armagh Observatory. It consisted of four hemispherical cups each mounted on one end of four horizontal arms, which in turn were mounted at equal angles to each other on a vertical shaft. The air flow past the cups in any horizontal direction turned the cups in a manner that was proportional to the wind speed. Therefore, counting the turns of the cups over a set time period produced the average wind speed for a wide range of speeds. On an anemometer with four cups it is easy to see that since the cups
    8.60
    5 votes
    3
    Hydrophone

    Hydrophone

    • Subclasses: Ocean Bottom Hydrophone
    A hydrophone (Greek "hydro" = "water" and "phone" = "sound") is a microphone designed to be used underwater for recording or listening to underwater sound. Most hydrophones are based on a piezoelectric transducer that generates electricity when subjected to a pressure change. Such piezoelectric materials, or transducers can convert a sound signal into an electrical signal since sound is a pressure wave. Some transducers can also serve as a projector, but not all have this capability, and may be destroyed if used in such a manner. A hydrophone can "listen" to sound in air, but will be less sensitive due to its design as having a good acoustic impedance match to water, which is a denser fluid than air. Likewise, a microphone can be buried in the ground, or immersed in water if it is put in a waterproof container, but will give similarly poor performance due to the similarly bad acoustic impedance match. The earliest widely used design was the Fessenden oscillator, an electrodynamically driven clamped-edge circular plate transducer (not actually an oscillator) operating at 500, 1000, and later 3000 Hz. It was originally marketed as an underwater telegraph, rather than as sonar, but
    7.17
    6 votes
    5

    TDS meter

    A TDS Meter indicates the Total Dissolved Solids (TDS) of a solution, i.e. the concentration of dissolved solids in it. Since dissolved ionized solids such as salts and minerals increase the conductivity of a solution, a TDS meter measures the conductivity of the solution and estimates the TDS from that. Dissolved organic solids such as sugar and microscopic solid particles such as colloids, do not significantly affect the conductivity of a solution so a TDS meter does not include them in its reading. A TDS meter typically displays the TDS in parts per million (ppm). For example, a TDS reading of 1 ppm would indicate there is 1 milligram of dissolved solids in each kilogram of water.
    7.40
    5 votes
    6

    Multiphase flow meter

    A multiphase flow meter is a device used in the oil and gas industry to measure the individual phase flow rates of petroleum, water and gas mixtures produced during oil production processes. Knowledge of the individual fluid flow rates of a producing oil well is required to facilitate reservoir management, field development, operational control, flow assurance, and production allocation. Conventional solutions concerning two- and three-phase metering systems require expensive and cumbersome test separators, high maintenance, and field personnel intervention. These conventional solutions do not lend themselves to continuous monitoring or metering. Moreover, with diminishing oil resources, oil companies are now frequently confronted with the need to recover hydrocarbons from marginally economical reservoirs. In order to ensure economic viability of these accumulations, the wells may have to be completed subsea, or crude oil from several wells sent to a common production facility with excess processing capacity. The economic constraints on such developments do not lend themselves to the continued deployment of three-phase separators as the primary measurement devices. Consequently,
    8.75
    4 votes
    7
    Optical power meter

    Optical power meter

    An optical power meter (OPM) is a device used to measure the power in an optical signal. The term usually refers to a device for testing average power in fiber optic systems. Other general purpose light power measuring devices are usually called radiometers, photometers, laser power meters, light meters or lux meters. A typical optical power meter consists of a calibrated sensor, measuring amplifier and display. The sensor primarily consists of a photodiode selected for the appropriate range of wavelengths and power levels. On the display unit, the measured optical power and set wavelength is displayed. Power meters are calibrated using a traceable calibration standard such as a NIST standard. A traditional optical power meter responds to a broad spectrum of light, however the calibration is wavelength dependent. This is not normally an issue, since the test wavelength is usually known, however it has a couple of drawbacks. Firstly, the user must set the meter to the correct test wavelength, and secondly if there are other spurious wavelengths present, then wrong readings will result. Sometimes optical power meters are combined with a different test function such as an Optical
    8.25
    4 votes
    8
    International Prototype Meter

    International Prototype Meter

    The metre was originally defined as one ten-millionth of the distance between the North Pole and the equator at the longitude of Paris. Because of the difficulty of reproducing this measurement, a platinum bar nominally of that length was constructed in 1799 and housed in the Archives de la République in Paris. Because of the difficulty of precisely measuring the end-to-end length of a metal bar such as the 1799 prototype, the metre was redefined in 1889 as the distance between precision marks on a new 'X' shaped 90% platinum 10% iridium bar at 0 °C. This alloy was used because it does not oxidize, is hard, can be highly polished, and expands or contracts very little with temperature changes. The bar was kept at the headquarters of the International Bureau of Weights and Measures (BIPM) in Pavillon de Breteuil near Paris. Selected metrologists were authorized to travel there to duplicate the marks on to their own bars for regional and national prototypes. The new bar served as standard until 1960 when the metre was redefined in terms of the wavelength of light emitted by the krypton-86 isotope. The metre was redefined yet again in 1983 in terms of the speed of light. The speed of
    6.80
    5 votes
    9
    EMF Meter

    EMF Meter

    An EMF meter (or EMF detector) is a scientific instrument for measuring electromagnetic fields (abbreviated as EMF). Most meters measure the electromagnetic radiation flux density (DC fields) or the change in an electromagnetic field over time (AC fields), essentially the same as a radio antenna, but with quite different detection characteristics. There are many different types of EMF meters, but the two largest categories are single axis and tri-axis. Single axis meters are cheaper than a tri-axis meters, but take longer to complete a survey because the meter only measures one dimension of the field. Single axis instruments have to be tilted and turned on all three axes to obtain a full measurement. A tri-axis meter measures all three axes simultaneously, but these models tend to be more expensive. Electromagnetic fields can be generated by AC or DC currents. An EMF meter can measure AC electromagnetic fields, which are usually emitted from man-made sources such as electrical wiring, while gaussmeters or magnetometers measure DC fields, which occur naturally in Earth's geomagnetic field and are emitted from other sources where direct current is present... As most electromagnetic
    7.75
    4 votes
    10
    Protractor

    Protractor

    • Dimension measured: Angle
    A protractor is a square, circular or semicircular tool, typically made of transparent plastic, for measuring angles. Most protractors measure angles in degrees (°). They are used for a variety of mechanical and engineering-related applications, but perhaps the most common use is in geometry lessons in schools. Some protractors are simple half-discs. More advanced protractors, such as the bevel protractor, have one or two swinging arms, which can be used to help measure the angle. A bevel protractor is a graduated circular protractor with a pivoted arm; used for measuring or marking off angles. Sometimes Vernier scales are attached to give more precise readings. It has wide application in architectural and mechanical drawing, although its use is decreasing with the availability of modern drawing software or CAD. Universal bevel protractors are also used by toolmakers; as they measure angles by mechanical contact they are classed as mechanical protractors. The bevel protractor is used to establish and test angles to very close tolerances. It reads to 5 minutes or 1/12° and can measure any angle from 0° to 360°. The bevel protractor consists of a beam, a graduated dial and a blade
    7.75
    4 votes
    11

    Lane meter

    According to the University of North Carolina's How Many? A Dictionary of Units of Measurement A lane meter is:
    9.33
    3 votes
    12
    VU meter

    VU meter

    A Volume Unit (VU) meter or Standard Volume Indicator (SVI) is a device displaying a representation of the signal level in audio equipment. The ASA standardized it in 1942 ( C16-5 - 1942) for use in telephone installation and radio broadcast stations. Consumer audio equipment often features VU meters, either because they are useful (basically in sound recording equipment), or just for their looks. The original VU meter is a passive electromechanical device, namely a 200µA DC d'Arsonval movement ammeter fed from a full wave copper-oxide rectifier mounted within the meter case. The mass of the needle causes a relatively slow response, which in effect integrates the signal, with a rise time of 300ms. The meter was designed not to measure the signal, but to let users aim the signal level to a target level of 0dB (sometimes labelled 100%), so it is not important that the device is non-linear and imprecise for low levels. In effect, the scale ranges from −20dB to +3dB, with −3dB right in the middle. Purely electronic devices may emulate the response of the needle; they are VU-meters inasmuch as they respect the standard. The VU-meter (intentionally) "slows" measurement, averaging out
    9.33
    3 votes
    13

    Declinometer

    • Dimension measured: Magnetic declination
    A declinometer is an instrument for measuring magnetic declination. The word comes from decline (through Middle English and Old French from the Latin de- "down" + clinare "to bend") + -meter.
    7.50
    4 votes
    14
    Hygrometer

    Hygrometer

    • Dimension measured: Relative humidity
    A hygrometer UK /haɪˈɡrɒmɪtə/ is an instrument used for measuring the moisture content in the environment. Humidity measurement instruments usually rely on measurements of some other quantity such as temperature, pressure, mass or a mechanical or electrical change in a substance as moisture is absorbed. By calibration and calculation, these measured quantities can lead to a measurement of humidity. Modern electronic devices use temperature of condensation, or changes in electrical capacitance or resistance to measure humidity changes. The familiar metal/paper coil hygrometer is useful for giving a dial indication of humidity changes, but it appears most often in very inexpensive devices and their accuracy is very limited. A search through many identical units in a display might show differences in indicated humidity of 10% or more. In these devices, humidity is absorbed by a salt-impregnated paper strip attached to a metal coil, causing it to change shape. These changes in length (analogous to those in a bimetallic thermometer) cause an indication on a dial. These devices use a human or animal hair under tension. The length of the hair changes with humidity and the length change
    7.50
    4 votes
    15

    Survey meter

    Survey meters are portable radiation detection and measurement instruments used to check personnel, equipment and facilities for radioactive contamination, or to measure external or ambient ionizing radiation fields (to evaluate the direct exposure hazard). The hand-held survey meter is probably the most familiar radiation measuring device to society owing to its wide and highly visible use. The following instrument types are the most commonly used as hand-held survey meters. The primary practical applications are listed. Used for alpha, beta and neutron measurement Used for alpha, beta and gamma measurement Used for gamma and X-ray measurement The instruments are designed to be hand-held, are battery powered and of low mass to allow easy manipulation. Other features include an easily readable display, in counts or radiation dose units, and an audible indication of the count rate. This is usually the “click” associated with the Geiger type instrument, and can also be an alarm warning sound when a rate of radiation counts or dose has been exceeded. These features allow the user to concentrate on manipulation of the meter whilst having auditory feedback of the rate of radiation
    7.50
    4 votes
    16

    Watercut meter

    A water cut meter measures the water content (cut) of crude oil and hydrocarbons as they flow through a pipeline. While the title "Water cut" has been traditionally used, the current API naming is OWD or On-Line Water Determination. The API and ISO committees as of yet have not come out with an international standard for these devices but there is however a standard in place for fiscal automatic sampling of crude oil namely API 8.2 and ISO 3171. Water cut meters are typically used in the mineral oil industry to measure the water cut of oil flowing from a well, produced oil from a separator, crude oil transfer in pipelines and in loading tankers. There are several technologies used. The main technologies are dielectric measurements using radio or microwave frequency and NIR measurements and less common are nuclear based instruments.
    7.50
    4 votes
    17
    Ammeter

    Ammeter

    • Dimension measured: Electric current
    An ammeter is a measuring instrument used to measure the electric current in a circuit. Electric currents are measured in amperes (A), hence the name. Instruments used to measure smaller currents, in the milliampere or microampere range, are designated as milliammeters or microammeters. Early ammeters were laboratory instruments which relied on the Earth's magnetic field for operation. By the late 19th century, improved instruments were designed which could be mounted in any position and allowed accurate measurements in electric power systems. The relation between electric current, magnetic fields and physical forces was first noted by Hans Christian Ørsted who, in 1820, observed a compass needle was deflected from pointing North when a current flowed in an adjacent wire. The tangent galvanometer was used to measure currents using this effect, where the restoring force returning the pointer to the zero position was provided by the Earth's magnetic field. This made these instruments usable only when aligned with the Earth's field. Sensitivity of the instrument was increased by using additional turns of wire to multiply the effect – the instruments were called "multipliers". The
    7.25
    4 votes
    19
    Clamp meter

    Clamp meter

    A clamp meter (clamp-on ammeter) is a type of ammeter that measures electrical current without the need to disconnect the wiring through which the current is flowing. Clamp meters are also known as tong testers or Amprobes (after one of the first vendors of such devices). The most common forms of clamp meter are: In order to use a clamp meter, the probe or clamp is opened to allow insertion of the wiring, and then closed to allow the measurement. Only one conductor is normally passed through the probe; if more than one conductor were to be passed through then the measurement would be a vector sum of the currents flowing in the conductors and could be very misleading depending on the phase relationship of the currents. In particular, if the clamp were to be closed around a mains extension or similar cord, no current will be measured at all as the current flowing in one direction will cancel that flowing in the other direction. In practice, nearly all clamp meters are used by electricians and the meters often include additional circuitry to allow the reading of voltage and, sometimes, resistance. The meters also often contain a mechanical pointer-locking device so that a reading can
    8.67
    3 votes
    20
    Microwave power meter

    Microwave power meter

    A microwave power meter is an instrument which measures the electrical power at microwave frequencies. Usually a microwave power meter will consist of a measuring head which contains the actual power sensing element, connected via a cable to the meter proper, which displays the power reading. The head may be referred to as a power sensor or mount. Different power sensors can be used for different frequencies or power levels. Historically the means of operation in most power sensor and meter combinations was that the sensor would convert the microwave power into an analogue voltage which would be read by the meter and converted into a power reading. Several modern power sensor heads contain electronics to create a digital output and can be plugged via USB into a PC which acts as the power meter. Microwave power meters have a wide bandwidth—they are not frequency-selective. To measure the power of a specific frequency component in the presence of other signals at different frequencies a spectrum analyzer or measuring receiver is needed. There are a variety of different technologies which have been used as the power sensing element. Each has advantages and disadvantages. Thermal
    8.67
    3 votes
    21
    Acoustic Doppler Current Profiler

    Acoustic Doppler Current Profiler

    An Acoustic Doppler Current Profiler (ADCP or ADP) is a hydroacoustic current meter similar to a sonar, attempting to measure water current velocities over a depth range using the Doppler effect of sound waves scattered back from particles within the water column. The term ADCP is used synonymously for all kind of acoustic current meters although the abbreviation originates from the name of an instrument series by Teledyne. ADCPs are commercially available since the late 1980s. The working frequencies range from 38 kHz to several megahertz. ADCPs contain piezoelectric oscillators to transmit and receive sound signals. The traveling time of sound waves gives an estimate of the distance, the red or blue shift can be converted to a velocity. In order to measure 3D velocities, at least three vector components have to be estimated, this is why the instruments has four of them. Further components of an ADCP are an electronic amplifier, a receiver, a mixer, a clock to measure the traveling time, a temperature sensor, a compass to know the relative rotation, and a pitch/roll sensor to know the horizontal. A analog-to-digital converter and a digital signal processor are required to sample
    7.00
    4 votes
    22
    Parking meter

    Parking meter

    A parking meter is a device used to collect money in exchange for the right to park a vehicle in a particular place for a limited amount of time. Parking meters can be used by municipalities as a tool for enforcing their integrated on-street parking policy, usually related to their traffic and mobility management policies. An early patent for a parking meter, US patent 1,731,839, was filed by Roger W. Babson, on August 30, 1928. The meter was intended to operate on power from the battery of the parking vehicle and required a connection from the vehicle to the meter. Holger George Thuesen and Gerald A. Hale designed the first working parking meter, the Black Maria, in 1935. The History Channel's... History's Lost and Found documents their success in developing the first working parking meter. Thuesen and Hale were engineering professors at Oklahoma State and began working on the parking meter in 1933 at the request of Carl C. Magee of Oklahoma City, Oklahoma, United States. The world's first installed parking meter was in Oklahoma City on July 16, 1935. Industrial production started in 1936 and expanded until the mid 1980s. The first models were based on a coin acceptor, a dial to
    8.33
    3 votes
    23
    Theodolite

    Theodolite

    • Subclasses: Ramsden theodolite
    A theodolite (/θiːˈɒdəlaɪt/) is a precision instrument for measuring angles in the horizontal and vertical planes. Theodolites are mainly used for surveying applications, and have been adapted for specialized purposes in fields like metrology and rocket launch technology. A modern theodolite consists of a movable telescope mounted within two perpendicular axes—the horizontal or trunnion axis, and the vertical axis. When the telescope is pointed at a target object, the angle of each of these axes can be measured with great precision, typically to seconds of arc. Transit refers to a specialized type of theodolite developed in the early 19th century. It featured a telescope that could "flip over" ("transit the scope") to allow easy back-sighting and doubling of angles for error reduction. Some transit instruments were capable of reading angles directly to thirty seconds. In the middle of the 20th century, "transit" came to refer to a simple form of theodolite with less precision, lacking features such as scale magnification and micrometers. Although precise electronic theodolites have become widespread tools, the transit still finds use as a lightweight tool on construction sites.
    8.33
    3 votes
    24

    MOCNESS

    MOCNESS is the acronym for Multiple Opening/Closing Net and Environmental Sensing System and is a net system for plankton in the ocean. The system is towed behind a research vessel with a speed of 1.5 knots and consists of five to twenty nets with a mesh size from 64 µm to 3 mm and an area of 1 to 10 sqm which are opened and closed computer controlled at desired depth. The net enables biologists to catch zooplankton and nekton in various depth horizons typically anywhere in the upper 500 m of the oceans. All MOCNESS systems are capable of sampling to 6000 meters depth (10,000 psi). The system includes a SeaBird CTD-probe to measure salinity and temperature at sampling depths, as well as optional dissolved oxygen, PAR (photosynthetically available light), transmissometry and fluorescence sensors. P. H. Wiebe et al., 1985, New development in the MOCNESS, an apparatus for sampling zooplankton and micronekton, Marine Biology, 87(3), 313-323, doi:10.1007/BF00397811
    10.00
    2 votes
    25

    Gyro-Theodolite

    • Subclass of: Theodolite
    The gyrotheodolite is a theodolite used for surveys which do not have sky visibility (mining, underground survey). This instrument gives the orientation of the [[true North (the direction of Earth's rotational axis) which is set as a reference for future underground observations. The gyro-theodolite is composed of a theodolite with a gyroscope on it. We obtain the true North by: When the gyro stabilized the reading on the horizontal circle of the theodolite is equivalent to North. http://www.geodesy.hu/gyrotheodolites.html
    6.75
    4 votes
    26

    Cent-a-meter

    The Cent-a-meter, known as the electrisave and the Owl in the UK, is an electricity usage monitor featuring an indoor wireless display. The user can monitor ongoing energy use, or switch on electrical devices and observe their power consumption and energy cost. The device can be configured to sound an alarm for excessive energy usage.
    6.50
    4 votes
    27
    Sound level meter

    Sound level meter

    A sound level meter or sound meter is an instrument which measures sound pressure level, commonly used in noise pollution studies for the quantification of different kinds of noise, especially for industrial, environmental and aircraft noise. However, the reading from a sound level meter does not correlate well to human-perceived loudness, which is better measured by a loudness meter. The current international standard that specifies sound level meter functionality and performance is the IEC 61672:2003. The IEC 61672-1 specifies "three kinds of sound measuring instruments". They are the "conventional" sound level meter, the integrating-averaging sound level meter, and the integrating sound level meter. The standard sound level meter can be called an exponentially averaging sound level meter as the AC signal from the microphone is converted to DC by a root-mean-square (RMS) circuit and thus it must have a time-constant of integration; today referred to as the time-weighting. Three of these time-weightings have been internationally standardised, 'S' (1 s) originally called Slow, 'F' (125 ms originally called Fast and 'I' (35 ms) originally called Impulse. Their names were changed in
    6.50
    4 votes
    28
    5.40
    5 votes
    29

    Displacement Volumetric Meter

    A Displacement Volumetric Meter is a device which measures total volume. It can operate on the principle of the fluid sweeping out a fixed calibrated volume, which produces a rotation of a calibrated gauge. an analogy can be drawn like this.suppose water is falling in a basin and a boy is putting small glass under the tap.after the glass is filled then it is replaced by another glass which is again filled.so total number of glass multiplied by volume of each glass divided by total time to carry out the task gives the displacement volumetric flow measurement.By maintaining constant conditions and taking readings over a prescribed period the flow rate can be calculated for the specific operating conditions. The instrument essentially measures total volume. Some water meters work on the principal to measure fixed volumes of water for billing. These are commonly referred to as "positive displacement meter".
    9.50
    2 votes
    30

    OBS: Ocean Bottom Seismometer

    • Subclass of: Seismometer
    An ocean-bottom seismometer (OBS) is a seismometer that is designed to record the earth motion under oceans and lakes from man-made sources and natural sources. Sensors at the sea floor are used to observe acoustic and seismic events. Seismic and acoustic signals may be caused by different sources, by earth quakes and tremors as well as by artificial sources. Computing and analyzing the data yields information about the kind of source and, in case of natural seismic events, the geophysics and geology of the sea floor and the deeper crust. The deployment of OBS along a profile will give information about the deep structure of the Earth's crust and upper mantle in offshore areas. OBS may be equipped with a maximum of a three-component geophone in addition to a hydrophone, and thus it needs a capacity of more than 144 Mbytes, which would be the minimum for an adequate MCS profiling. In a typical survey, the instruments should be operational for several days, which requires a data storage capacity of more than 500 Mbyte. Other experiments, such as tomographic investigations within a 3D-survey or seismological monitoring, demand even larger capacities. The OBS consists of an aluminum
    7.67
    3 votes
    31

    Postage meter

    A postage meter is a mechanical device used to create and apply physical evidence of postage (or franking) to mailed matter. Postage meters are regulated by a country's postal authority; for example, in the United States, the United States Postal Service specifies the rules for the creation, support, and use of postage meters. A postage meter imprints an amount of postage, functioning as a postage stamp, a cancellation and a dated postmark all in one. The meter stamp serves as proof of payment and eliminates the need for adhesive stamps. Since the issuance of adhesive stamps in 1847, postal officials have been concerned about security against stamp theft and how to process mail in a timely fashion One solution was a postage stamp affixing machine, introduced in the 1880s. As early as 1884, a Norwegian, Engle Frankmussler (later anglisized to Edward Franks), obtained a British patent for a device that would print a “stamp” on an envelope and record the amount of postage by means of a counting device, or Franking machine, he presented this design at the 1886 Worlds Fair. Inventors in Germany, Norway, Australia, New Zealand and Great Britain pursued similar idea in the late 19th
    7.67
    3 votes
    32

    ESR meter

    An ESR meter is a two-terminal electronic measuring instrument designed and used primarily to measure the equivalent series resistance (ESR) of real capacitors—the ESR of an ideal capacitor is zero—usually without the need to disconnect the capacitor from the circuit it is connected to. Most ESR meters work by applying voltage pulses to the capacitor under test which are too short to appreciably charge it; any voltage appearing across the capacitor is due to ohmic drop across the ESR. An alternating voltage at a frequency at which the capacitor's reactance is negligible, in a voltage divider configuration, can also be used. Other types of meter, including normal capacitance meters, cannot be used to measure capacitor ESR, although a few meters are available which measure both ESR and out-of-circuit capacitance. A normal (DC) milliohmmeter cannot be used to measure ESR, as a steady direct current cannot be passed through the capacitor. An ESR meter can always be used to measure low non-inductive resistances whether or not associated with a capacitor; this leads to a number of additional applications described below. Aluminium electrolytic capacitors have a relatively high ESR that
    6.25
    4 votes
    33

    People meter

    A people meter is a audience measurement tool used to measure the viewing habits of TV and cable audiences. The People Meter is a 'box', about the size of a paperback book. The box is hooked up to each television set and is accompanied by a remote control unit. Each family member in a sample household is assigned a personal 'viewing button'. It identifies each household member's age and sex. If the TV is turned on and the viewer doesn't identify themselves, the meter flashes to remind them. Additional buttons on the People Meter enable guests to participate in the sample by recording their age, sex and viewing status into the system. The device, known as a 'frequency-based meter', was invented by a British company called Audits of Great Britain (AGB). The successor company to AGB is TNS, which is active in 34 countries around the globe. Originally, these meters identified the frequency of the channels - VHF or UHF - watched on the viewer's TV set. This system became obsolete when Direct to Home (DTH) satellite dish became popular and viewers started to get their own satellite decoders. In addition, this system doesn't measure digital broadcasts. Before the People Meter advances,
    6.25
    4 votes
    34
    Accelerometer

    Accelerometer

    • Dimension measured: Proper acceleration
    • Subclasses: Gravimeter
    An accelerometer is a device that measures proper acceleration, also called the four-acceleration. This proper acceleration is associated with the weight of a test mass. For example, an accelerometer on a rocket far from any gravitational influences (assume gravitation is zero) that is accelerating through space due to the force from its engine, will measure the rate of change of the velocity of the rocket relative to any inertial frame of reference, because such changes require application of a (rocket) force that can be felt (as weight), for any mass. However, the proper acceleration measured by an accelerometer is not necessarily the coordinate acceleration (rate of change of velocity), when gravity becomes involved. Gravitation may make these types of acceleration differ. For an example where these types of acceleration differ, an accelerometer will measure a value of g in the upward direction when remaining stationary on the ground, because masses on earth have weight m*g. Such weight is transmitted from the push of the ground, and is not directly caused by gravity, but rather by the mechanical force from the ground, in the same way as the push of the engine in the rocket
    9.00
    2 votes
    35

    Par meter

    A peak-to-average ratio meter (Par meter) is a device used to measure the ratio of the peak power level to the time-averaged power level in an electrical circuit. This quantity is known as the peak-to-average ratio (p/a r or PAR). Such meters are used as a quick means to identify degraded telephone channels. Par meters are very sensitive to envelope delay distortion. They may also be used for idle channel noise, nonlinear distortion, and amplitude-distortion measurements. The peak-to-average ratio can be determined for many signal parameters, such as voltage, current, power, frequency, and phase.
    7.33
    3 votes
    36
    6.00
    4 votes
    37
    Side-scan sonar

    Side-scan sonar

    • Subclasses: Seamark Side Scan Sonar
    Side-scan sonar (also sometimes called side scan sonar, sidescan sonar, side looking sonar, side-looking sonar, side imaging sonar, side-imaging sonar and bottom classification sonar) is a category of sonar system that is used to efficiently create an image of large areas of the sea floor. It may be used to conduct surveys for maritime archaeology; in conjunction with seafloor samples it is able to provide an understanding of the differences in material and texture type of the seabed. Side-scan sonar imagery is also a commonly used tool to detect debris items and other obstructions on the seafloor that may be hazardous to shipping or to seafloor installations by the oil and gas industry. In addition, the status of pipelines and cables on the seafloor can be investigated using side-scan sonar. Side-scan data are frequently acquired along with bathymetric soundings and sub-bottom profiler data, thus providing a glimpse of the shallow structure of the seabed. Side-scan sonar is also used for fisheries research, dredging operations and environmental studies. It also has military applications including mine detection. Side-scan uses a sonar device that emits conical or fan-shaped pulses
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    38
    E-meter

    E-meter

    An E-meter is an electronic device used during Dianetics and Scientology auditing. The device is a variation of a Wheatstone bridge, which measures electrical resistance and skin conductance. It is formally known as the Hubbard Electrometer, after the Church's founder, L. Ron Hubbard. Most of the Scientology concepts associated with the "E-meter" and its use are regarded by the scientific and medical communities as pseudoscience. The device itself is essentially a modified ohmmeter. The Church of Scientology restricts the use of the E-meter to trained Scientologists, treating it as "a religious artifact used to measure the state of electrical characteristics of the 'static field' surrounding the body". The meter, when used by a trained Scientologist, is claimed to reflect or indicate whether or not a person has been relieved from spiritual impediment of past experiences. Officials within Scientology assert that the E-meter is intended for use only in Church-sanctioned auditing sessions and is in itself not a curative or medical device. The E-meters used by the Church of Scientology are manufactured by Scientologists at their Gold Base facility. The device's primary component is an
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    3 votes
    39
    Kearny Fallout Meter

    Kearny Fallout Meter

    The Kearny Fallout Meter or KFM is an expedient radiation meter. It is designed such that someone with a normal mechanical ability would be able to construct it before or during a nuclear attack and from common household items. The Kearny Fallout Meter was developed by Cresson Kearny from research performed at Oak Ridge National Laboratory, and published in the civil defense manual Nuclear War Survival Skills (ISBN 0-942487-01-X). The plans were originally released in Oak Ridge National Laboratory publication ORNL-5040, The KFM, A Homemade Yet Accurate and Dependable Fallout Meter and have been formatted in a newsprint ready layout so that they may be quickly printed with accurate dimensions in local newspapers. It must be built from a correctly scaled copy of the plans; photocopies and printouts of digital copies may not be to scale. Devised in 1978 by Cresson Kearny, the Kearny fallout meter is an application of the gold-leaf electroscope developed in 1787 by Abraham Bennet. Prior to this, the use of the electrometer principal for radiation detection had seen widespread application in the form of the quartz fiber dosimeter. Professional radiation meters, while more accurate and
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    3 votes
    40

    Trip meter

    Trip meter is the name given to an odometer in an automobile or other vehicle, which is designed to be reset at any desired point in a journey, so having the capability of recording the distance travelled in any particular journey or part of a journey. It was traditionally a purely mechanical device but, in most modern vehicles, it is now electronic.
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    3 votes
    41

    Q meter

    A Q meter is a piece of equipment used in the testing of radio frequency circuits. It has been largely replaced in professional laboratories by other types of impedance measuring device, though it is still in use among radio amateurs. It was developed at Boonton Radio Corporation in Boonton, New Jersey in 1934 by William D. Loughlin. A Q meter measures Q, the quality factor of a circuit, which expresses how much energy is dissipated per cycle in a non-ideal reactive circuit: This expression applies to an RF and microwave filter, bandpass LC filter, or any resonator. It also can be applied to an inductor or capacitor at a chosen frequency. For inductors Where XL is the reactance of the inductor, L is the inductance, ω is the angular frequency and R is the resistance of the inductor. The resistance R represents the loss in the inductor, mainly due to the resistance of the wire. For LC band pass circuits and filters: Where F is the resonant frequency (center frequency) and BW is the filter bandwidth. In a band pass filter using an LC resonant circuit, when the loss (resistance) of the inductor increases, its Q is reduced, and so the bandwidth of the filter is increased. In a coaxial
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    42
    Peak flow meter

    Peak flow meter

    The peak expiratory flow (PEF), also called peak expiratory flow rate (PEFR) is a person's maximum speed of expiration, as measured with a peak flow meter, a small, hand-held device used to monitor a person's ability to breathe out air. It measures the airflow through the bronchi and thus the degree of obstruction in the airways. Peak flow readings are higher when patients are well, and lower when the airways are constricted. From changes in recorded values, patients and doctors may determine lung functionality, severity of asthma symptoms, and treatment options. First measure of precaution would be to check patient for signs and symptoms of asthmatic hypervolemia. This would indicate whether or not to even continue with the Peak Flow Meter procedure. Measurement of PEFR requires training to correctly use a meter and the normal expected value depends on a patient's sex, age and height. It is classically reduced in obstructive lung disorders such as asthma. Due to the wide range of ‘normal' values and high degree of variability, peak flow is not the recommended test to identify asthma. However, it can be useful in some circumstances. A small proportion of people with asthma may
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    1 votes
    43
    Gas meter

    Gas meter

    A gas meter is used to measure the volume of fuel gases such as natural gas and propane. Gas meters are used at residential, commercial, and industrial buildings that consume fuel gas supplied by a gas utility. Gases are more difficult to measure than liquids, as measured volumes are highly affected by temperature and pressure. Gas meters measure a defined volume, regardless of the pressurized quantity or quality of the gas flowing through the meter. Temperature, pressure and heating value compensation must be made to measure actual amount and value of gas moving through a meter. Several different designs of gas meters are in common use, depending on the volumetric flow rate of gas to be measured, the range of flows anticipated, the type of gas being measured and other factors. These are the most common type of gas meter, seen in almost all residential and small commercial installations. Within the meter there are two or more chambers formed by movable diaphragms. With the gas flow directed by internal valves, the chambers alternately fill and expel gas, producing a near continuous flow through the meter. As the diaphragms expand and contract, levers connected to cranks convert the
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    44

    Laser accelerometer

    • Subclass of: Accelerometer
    A laser accelerometer comprises a frame having three orthogonal input axes and multiple proof masses, each proof mass having a predetermined blanking surface. A flexible beam supports each proof mass. The flexible beam permits movement of the proof mass on the input axis. A laser light source provides a light ray. The laser source is characterized to have a transverse field characteristic having a central null intensity region. A mirror transmits a ray of light to a detector. The detector is positioned to be centered to the light ray and responds to the transmitted light ray intensity to provide an intensity signal. The intensity signal is characterized to have a magnitude related to the intensity of the transmitted light ray. The proof mass blanking surface is centrally positioned within and normal to the light ray null intensity region to provide increased blanking of the light ray in response to transverse movement of the mass on the input axis. The proof mass deflects the flexible beam and moves the blanking surface in a direction transverse to the light ray to partially blank the light beam in response to acceleration in the direction of the input axis. A control responds to
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    3 votes
    45
    Meter Point Administration Number

    Meter Point Administration Number

    A Meter Point Administration Number, also known as MPAN, Supply Number or S-Number, is a 21-digit reference used in Great Britain to uniquely identify electricity supply points such as individual domestic residences. The gas equivalent is the Meter Point Reference Number. The system was introduced in 1998 in order to provide a competitive environment for the electricity companies, and allows consumers to switch their supplier easily as well as simplifying administration. Although the name suggests that an MPAN refers to a particular meter, an MPAN can have several meters associated with it, or indeed none where it is an unmetered supply. A supply receiving power from the network operator (DNO) has an Import MPAN, while generation and microgeneration projects feeding back into the DNO network are given Export MPANs. An MPAN is commonly separated into two sections: the core and the supplementary data. The core is the final 13 digits and is the unique identifier. The supplementary data gives information about the characteristics of the supply and is the responsibility of the supplier. The full MPAN is required to be depicted on electricity bills (the boxes on the top and bottom line
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    3 votes
    46
    Cycling power meter

    Cycling power meter

    A cycling power meter is a device on a bicycle that measures the power output of the rider. Most cycling power meters use strain gauges to measure torque applied, and, combined with angular velocity, calculate power. The Technology was adapted to cycling in the late 1980s and was tested in professional bicycle racing i.e.: the prototype Power Pacer (Team Strawberry) and by Greg LeMond with the SRM device. This type of power meter has been commercially available since 1989. Power meters using strain gauges are mounted in the bottom bracket, rear freehub, or crankset. Certain newer devices do not use strain gauges and instead measure power through handlebar-mounted units that utilize the principles of Newton's Third Law by measuring a cyclist's opposing forces (gravity, wind resistance, inertia, rolling resistance) and combining these with velocity to determine the rider's power output. Training using a power meter is increasingly popular. Power meters generally come with a handlebar mounted computer that displays information about the power output generated by the rider such as instantaneous, max, and average power. Most of these computers also serve as all-around cycling computers
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    47

    Multibeam echosounders

    • Subclasses: SeaBeam
    Multibeam echosounders, also known as Swathe (British English) or Swath (American English) echosounders, originated in the late 1950s, originally for military applications. They were developed in the 1970s by the US Navy, in conjunction with General Instrument to map large swaths of the ocean floor to assist the underwater navigation of its submarine force. Starting in the 1970s, companies such as General Instrument (now SeaBeam Instruments, part of L3 Klein) in the United States, Krupp Atlas (now Atlas Hydrographic) and Elac Nautik (now part of L3 Communications) in Germany, Simrad (now Kongsberg Maritime) in Norway and RESON in Denmark developed systems that could be mounted to the hull of large ships, and then small boats (as technologies improved and operating frequencies increased). The first commercial multibeam is now known as the SeaBeam Classic and was put in service in May 1977 (Harold Farr, Marine Geodesy, Volume 4, Issue 2 1980, pages 77 – 93) on the Australian survey vessel HMAS Cook. This system produced up to 16 beams across a 45-degree swath. The second SeaBeam Classic installation was on the French Research Vessel Jean Charcot sometime after the Cook. The SB
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    48
    Ramsden theodolite

    Ramsden theodolite

    • Subclass of: Theodolite
    The Ramsden theodolite is a large theodolite that was specially constructed for use in the first Ordnance Survey of Southern Britain. It was also known as the Great or 36 inch theodolite. The theodolite was commissioned from Jesse Ramsden, a leading Yorkshire instrument maker, who had developed an accurate dividing engine for graduating angular scales. The instrument was accurate to within a second of arc. The theodolite took three years to build and had a base circle of 3 ft (914 mm). The full survey, sometimes called the Principal Triangulation of Great Britain, was begun in 1791 by a team formed under General William Roy (d 1790).. The survey used the new theodolite on a specially surveyed baseline based on Roy's accurate surveys between London and Paris. Traces of the theodolite support structure were still to be found many years afterwards at some remote survey points, such as at Soldiers' Lump, the summit of Black Hill in the Peak District of England. The theodolite is now in the Science Museum in London. Ramsden, who was elected to the Royal Society in 1786, and was awarded the Copley Medal in 1795 for his instruments, also made important contributions to fields such as
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    49

    Peak meter

    A peak meter is a type of measuring instrument that indicates visually the instantaneous level of an audio signal that is passing through it (a sound level meter). In sound reproduction, the meter, whether peak or not, is usually meant to correspond to the perceived loudness of a particular signal. In modern audio equipment, peak meters are usually made up of a series of LEDs (small lights) that are placed in a vertical or horizontal bar and lit up sequentially as the signal increases. There are many variations on how this is implemented. They typically have ranges of green, yellow, and red, to indicate when a signal is starting to overload. The term "peak" is used to denote the meter's ability, regardless of the type of visual display, to indicate the highest output level at any instant. A peak meter can also be implemented with a classic moving needle device such as those on older analog equipment (similar in appearance in some ways to a pressure gauge on a bicycle pump), or by other means. Older equipment used actual moving parts instead of lights to indicate the audio level. Because of the mass of the moving parts and mechanics, the response time of these older meters could
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    3 votes
    50
    Piezoelectric accelerometer

    Piezoelectric accelerometer

    • Subclass of: Accelerometer
    A piezoelectric accelerometer that utilizes the piezoelectric effect of certain materials to measure dynamic changes in mechanical variables. (e.g. acceleration, vibration, and mechanical shock) As with all transducers, piezoelectric accelerometers convert one form of energy into another and provide an electrical signal in response to a quantity, property, or condition that is being measured. Using the general sensing method upon which all accelerometers are based, acceleration acts upon a seismic mass that is restrained by a spring or suspended on a cantilever beam, and converts a physical force into an electrical signal. Before the acceleration can be converted into an electrical quantity it must first be converted into either a force or displacement. This conversion is done via the mass spring system shown in the figure to the right. The word piezoelectric finds its roots in the Greek word piezein, which means to squeeze or press. When a physical force is exerted on the accelerometer, the seismic mass loads the piezoelectric element according to Newton’s second law of motion (). The force exerted on the piezoelectric material can be observed in the change in the electrostatic
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    3 votes
    51
    Mooring

    Mooring

    A mooring in oceanography is a collection of devices, connected to a wire and anchored on the sea floor. It is the Eulerian way of measuring ocean currents, since a mooring is stationary at a fixed location. In contrast to that, the Lagrangian way measures the motion of an oceanographic drifter, see Lagrangian drifter. The mooring is held up in the water column with various forms of buoyancy such as glass balls and syntactic foam floats. The attached instrumentation is wide ranging but often includes CTDs (conductivity, temperature depth sensors), current meters (e.g. acoustic Doppler current profilers or deprecated rotor current meters), biological sensors, and other devices to measure various parameters. Long-term moorings can be deployed for durations of two years or more, powered with alkaline or lithium battery packs. Moorings often include surface buoys that transmit real time data back to shore. The traditional approach is to use the Argos System. Alternatively, one may use the commercial Iridium satellites which allow higher data rates. In deeper waters or areas covered by sea ice, moorings are often completely submerged with no surface markers. Submerged moorings use an
    9.00
    1 votes
    52

    Air-fuel ratio meter

    An air–fuel ratio meter monitors the air–fuel ratio of an internal combustion engine. Also called air–fuel ratio gauge, air–fuel meter, or air–fuel gauge. It reads the voltage output of an oxygen sensor, sometimes also called lambda sensor, whether it be from a narrow band or wide band oxygen sensor. The original narrow-band oxygen sensors became factory installed standard in the late 1970s and early 80s. In recent years, a newer and much more accurate wide-band sensor, though more expensive, has become available. Most stand-alone narrow-band meters have 10 LEDs and some have more. Also common, narrow band meters in round housings with the standard mounting 2 1/16" and 2 5/8" diameters, as other types of car 'gauges'. These usually have 10 or 20 LEDs. Analogue 'needle' style gauges are also available. As stated above, there are wide-band meters that stand alone or are mounted in housings. Nearly all of these show the air–fuel ratio on a numeric display, since the wide-band sensors provide a much more accurate reading. And since they use more accurate electronics, these meters are more expensive. Lean mixtures improve the fuel economy but also cause sharp rises in the amount of
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    2 votes
    53
    Clock

    Clock

    • Dimension measured: Time
    • Subclasses: Cuckoo clock
    A clock is an instrument used to indicate, keep, and co-ordinate time. The word clock is derived ultimately (via Dutch, Northern French, and Medieval Latin) from the Celtic words clagan and clocca meaning "bell". A silent instrument missing such a mechanism has traditionally been known as a timepiece. In general usage today a "clock" refers to any device for measuring and displaying the time. Watches and other timepieces that can be carried on one's person are often distinguished from clocks. The clock is one of the oldest human inventions, meeting the need to consistently measure intervals of time shorter than the natural units: the day; the lunar month; and the year. Devices operating on several different physical processes have been used over the millennia, culminating in the clocks of today. The study of timekeeping is known as horology. The sundial, which measures the time of day by using the sun casting a shadow onto a cylindrical stone, was widely used in ancient times. A well-constructed sundial can measure local solar time with reasonable accuracy, and sundials continued to be used to monitor the performance of clocks until the modern era. However, its practical
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    54

    Concrete moisture meter

    A concrete moisture meter is a type of moisture meter used by installers of flooring to measure the moisture levels of concrete. These meters have been used for decades to measure the moisture content in different materials and substances. Concrete meters have evolved from the successful wood moisture meter as flooring contractors tried to use their wood meters to measure the moisture in concrete. Concrete moisture meters are designed to detect moisture to a depth of 1” of a concrete slab in order to avoid the rebar reinforcement below the surface. They are designed to be used as a relative test. The meters are used to “‘Spot check’ the top surface at one particular location on the slab.” The results can determine the best place to put a concrete relative humidity test. There is no ASTM standard for using a concrete moisture meter to determine a final moisture content reading. Concrete moisture meters, either non-pin or pin meters are affected by what it sees in the concrete. This can be anything from the density of the concrete and aggregate size to the chemical properties of the slab. Uncovered concrete dries from the top down. Concrete moisture meters measure only the top inch
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    2 votes
    55

    Handle-o-Meter

    The Handle-o-Meter is a testing machine developed by Johnson & Johnson and now manufactured by Thwing-Albert that measures the "handle", i.e. a combination of surface friction and flexibility of sheeted materials. Originally it was used to test the durability and flexibility of toilet paper and paper towels. The test sample is placed over an adjustable slot. The resistance encountered by the penetrator blade as it is moved into the slot by a pivoting arm is measured.
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    2 votes
    56
    Hobbs Meter

    Hobbs Meter

    The Hobbs Meter records the time a device is used. It is frequently used in aviation applications to record the time that the electrical power (battery master switch) is "on". Hobbs is a genericized trademark for products generically called "Engine Hour Meters". The meters run electrically, indicating hours and tenths of an hour, but there are several ways a meter may record the "Hobbs Time": For general aviation, Hobbs Time is usually recorded in the pilot's log book, and many Fixed-Base Operations that rent airplanes charge an hourly rate based on Hobbs Time. Tach Time is recorded in the engine's log books and is used, for example, determining when the oil should be changed and the time between overhauls. Tach (tachometer) time differs from Hobbs Time in that it is linked to engine revolutions per minute (RPM). Tach Time records the time at some specific RPM. It is most accurate at cruise RPM, and least accurate while taxiing or stationary with the engine running. At these times, the clock runs slower. Depending on the type of flight, Tach Time can be 10–20% less than Hobbs Time. Many organizations such as flying clubs charge by Tach Time so as to differentiate themselves from
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    2 votes
    57

    Tension meter

    A tension meter is a device used to measure tension in wires, cables, textiles, belts and more. Meters commonly use a 3 roller system where the material travels through the rollers causing deflection in the center roller that is connected to an analog indicator or load cell on digital models. Single roll tension sensors and sonic tension meters are other types of tension meters. Tension meters are available as handheld devices or as equipment for fixed installations. These are basically necessary to build up a tension-controlled closed loop.
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    2 votes
    58

    Thermal mass flow meter

    There are two types of thermal flow meters in industry. Industrial thermal mass flow meters, also known as thermal dispersion or immersible mass flow meters comprise a family of instruments for the measurement of the total mass flow rate of a fluid, primarily gases, flowing through closed conduits. A second type is the capillary-tube type of thermal mass flow meter. Many mass flow controllers (MFC) which combine a mass flow meter, electronics and a valve are based on this design. Both types measure fluid mass flow rate by means of the heat convected from a heated surface to the flowing fluid. In the case of the thermal dispersion, or immersible, type of flow meter, the heat is transferred to the boundary layer of the fluid flowing over the heated surface. In the case of the capillary-tube type, the heat is transferred to the bulk of the fluid flowing through a small heated capillary tube. The principles of operation of the two types are both thermal in nature, but are so substantially different that two separate standards are required. Additionally, their applications are much different. Thermal dispersion flow meters are commonly used for general industrial gas flow applications
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    2 votes
    60

    Magnetic flow meter

    The third most common flowmeter behind differential pressure and positive displacement flow meters, is the magnetic flow meter, also technically an electromagnetic flow meter or more commonly just called a mag meter. A magnetic field is applied to the metering tube, which results in a potential difference proportional to the flow velocity perpendicular to the flux lines. The physical principle at work is electromagnetic induction. The magnetic flow meter requires a conducting fluid, for example, water that contains ions, and an electrical insulating pipe surface, for example, a rubber-lined steel tube. Usually electrochemical and other effects at the electrodes make the potential difference drift up and down, making it hard to determine the fluid flow induced potential difference. To mitigate this, the magnetic field is constantly reversed, cancelling out the static potential difference. This however impedes the use of permanent magnets for magnetic flowmeters.
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    1 votes
    61
    Mass flow meter

    Mass flow meter

    A mass flow meter, also known as an inertial flow meter is a device that measures mass flow rate of a fluid traveling through a tube. The mass flow rate is the mass of the fluid traveling past a fixed point per unit time. The mass flow meter does not measure the volume per unit time (e.g., cubic meters per second) passing through the device; it measures the mass per unit time (e.g., kilograms per second) flowing through the device. Volumetric flow rate is the mass flow rate divided by the fluid density. If the density is constant, then the relationship is simple. If the fluid has varying density, then the relationship is not simple. The density of the fluid may change with temperature, pressure, or composition, for example. The fluid may also be a combination of phases such as a fluid with entrained bubbles. There are two basic configurations of coriolis flow meter: the curved tube flow meter and the straight tube flow meter. This article discusses the curved tube design. The animations on the right do not represent an actually existing coriolis flow meter design. The purpose of the animations is to illustrate the operating principle, and to show the connection with rotation. Fluid
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    1 votes
    62
    PH meter

    PH meter

    A pH meter is an electronic device used for measuring the pH (acidity or alkalinity) of a liquid (though special probes are sometimes used to measure the pH of semi-solid substances). A typical pH meter consists of a special measuring probe (a glass electrode) connected to an electronic meter that measures and displays the pH reading. The pH probe measures pH as the activity of the hydrogen cations surrounding a thin-walled glass bulb at its tip. The probe produces a small voltage (about 0.06 volt per pH unit) that is measured and displayed as pH units by the meter. For more information about pH probes, see glass electrode. For very precise work the pH meter should be calibrated before each measurement. For normal use calibration should be performed at the beginning of each day. The reason for this is that the glass electrode does not give a reproducible e.m.f. over longer periods of time. Calibration should be performed with at least two standard buffer solutions that span the range of pH values to be measured. For general purposes buffers at pH 4 and pH 10 are acceptable. The pH meter has one control (calibrate) to set the meter reading equal to the value of the first standard
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    1 votes
    63
    Seismometer

    Seismometer

    • Subclasses: OBS: Ocean Bottom Seismometer
    Seismometers are instruments that measure motions of the ground, including those of seismic waves generated by earthquakes, volcanic eruptions, and other seismic sources. Records of seismic waves allow seismologists to map the interior of the Earth, and locate and measure the size of these different sources. The word derives from the Greek σεισμός, seismós, a shaking or quake, from the verb σείω, seíō, to shake; and μέτρον, métron, measure and was coined by David Milne-Home in 1841. Seismograph is another Greek term from seismós and γράφω, gráphō, to draw. It is often used to mean seismometer, though it is more applicable to the older instruments in which the measuring and recording of ground motion were combined than to modern systems, in which these functions are separated. Both types provide a continuous record of ground motion; this distinguishes them from seismoscopes, which merely indicate that motion has occurred, perhaps with some simple measure of how large it was. Inertial seismometers have levers in them that keep rhythmic motion Any motion of the ground moves the frame. The mass tends not to move because of its inertia, and by measuring the motion between the frame and
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    1 votes
    64
    SWR meter

    SWR meter

    The SWR meter or VSWR (voltage standing wave ratio) meter measures the standing wave ratio in a transmission line. The meter can be used to indicate the degree of mismatch between a transmission line and its load (usually a radio antenna), or evaluate the effectiveness of impedance matching efforts. A directional SWR meter measures the magnitude of the forward & reflected waves by sensing each one individually, with directional couplers. A calculation can then be performed to arrive at the SWR. Referring to the above diagram, the transmitter (TX) and antenna (ANT) terminals are connected via an internal transmission line. This main line is electromagnetically coupled to two smaller sense lines (directional couplers) which are terminated with resistors at one end, and diode rectifiers at the other. Sometimes a printed circuit board using three parallel traces is used to make the transmission line and the two sensing lines. The resistors are chosen to match the characteristic impedance of the sense lines. The diodes convert the magnitudes of the forward & reverse waves to FWD and REV DC voltages, respectively, which are then smoothed by the capacitors. To calculate the VSWR, first
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    1 votes
    65
    EC meter

    EC meter

    • Dimension measured: Conductivity
    An electrical conductivity meter (EC meter) measures the electrical conductivity in a solution. Commonly used in hydroponics, aquaculture and freshwater systems to monitor the amount of nutrients, salts or impurities in the water. The common laboratory conductivity meters employ a potentiometric method and four electrodes. Often, the electrodes are cylindrical and arranged concentrically. The electrodes are usually made of platinum metal. An alternating current is applied to the outer pair of the electrodes. The potential between the inner pair is measured. Conductivity could in principle be determined using the distance between the electrodes and their surface area using the Ohm's law but generally, for accuracy, a calibration is employed using electrolytes of well-known conductivity. Industrial conductivity probes often employ an inductive method, which has the advantage that the fluid does not wet the electrical parts of the sensor. Here, two inductively-coupled coils are used. One is the driving coil producing a magnetic field and it is supplied with accurately-known voltage. The other forms a secondary coil of a transformer. The liquid passing through a channel in the sensor
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    66

    Fixed Survey Meter

    The Fixed Survey Meter was a specialist detection instrument used by the Royal Observer Corps during the Cold War between 1958 and 1982 to detect ionising radiation from nuclear fallout generated by a ground burst. The instrument was designed and built by the Atomic Weapons Establishment at Aldermaston as a replacement for the Radiac Survey Meter No 2 which could only be used above ground. The Royal Observer Corps’ need was for an instrument that could be read from inside the protected environment on the underground post. The instrument had an analogue mechanical dial with a pivoted needle indicator on a scale that covered 0.1 roentgens to 500 roentgens. Powered by three obsolete high voltage batteries (15 volt and 30 volt), that had to be specially manufactured, the meter was contained in a sturdy enamelled metal case. The controls featured an on-off switch combined with a calibration adjustment and a multi-position battery test switch. The batteries were contained within a clip-on cassette that took several minutes of careful preparation. A spare cassette was also pre-prepared to enable quick battery changes during operations. The meter was connected by a heavy duty cable to an
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    67

    Portable People Meter

    The Portable People Meter (PPM) is a system developed by Arbitron to measure how many people are listening (or at least exposed) to individual radio stations and television stations, including cable TV. The PPM is worn like a pager, and detects hidden audio tones within a station or network's audio stream, logging each time it finds such a signal. It has proved to be much more accurate than the old handwritten logs or wired meters, and is immune to forgetful test subjects. There are several parts to the PPM system: The system can also be used for other media, such as movies and music which are recorded with a digital encoding. Various venues and retail locations are also encoding their media in the Houston area. The original concept for the PPM can be traced back to a brainstorming session at Arbitron in November 1988. At that time, concerns over the forthcoming move from analog video to high-definition digital television had engineers concerned that the technology currently in use would become obsolete overnight. Drawing upon his experience in testing labs, Dr. Gerald Cohen proposed embedding an identifying signal in the audio and later decoding it. The rationale was simple. Dr.
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    2 votes
    68

    Velocity air meter

    A Velocity air meter measures the force of air rushing into an engine against a spring-loaded door in an air tunnel. A linear potentiometer rotated along with the hinge of the air door measures the angle of the opening and sends an electrical signal to the engine control unit (ECU) that changes as the door opens more or less. The ECU can deduce airflow into the engine based on this value after making certain corrections. The problem is that the force against the door is a function of two variables - weight of the air and speed of the air - and the ECU cannot distinguish, for a given door angle, whether the air is less dense but traveling faster or whether the air is denser but traveling more slowly. Therefore air velociy must be corrected for air density (temperature and barometric pressure) in order to reflect air mass (actual number of air molecules entering the engine per unit of time). Velocity air meters from Bosch have been commonly used on systems such as older Bosch L-Jetronic and as a part of many factory systems, though they now have mostly been superseded by mass airflow sensors which have many advantages and are less damaging to engine volumetric efficiency (VE).
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    2 votes
    69

    Video plankton recorder

    A video plankton recorder (VPR) is towed underwater video microscope system, which photographs small to fine-scale structure of plankton, from 50 micrometers and up to a few centimeters in size. A VPR consists of five general components: cameras (with magnifying optics ), strobe, additive sensor and flight control, underwater platform and interface software for plankton identification. In order to obtain high-quality and low-noise images, charge-coupled device (CCD) sensors are used in the camera system. In the early design system, the CCD cameras were mounted in one of the arm of the platform. The developments in the recent years made the cameras system possible to be mounted in the platform body along with other sensors and flight control. The magnification power on the cameras should be vary, with high magnification power on the camera, we can obtain detail observation result on the plankton sample, such as protozoan that has
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    2 votes
    70
    Water meter

    Water meter

    A water meter is a device used to measure the volume of water usage. In many developed countries water meters are used to measure the volume of water used by residential and commercial building that are supplied with water by a public water supply system. Water meters can also be used at the water source, well, or throughout a water system to determine flow through that portion of the system. In most of the world water meters measure flow in Cubic metres (m) or litres but in the USA and some other countries water meters are calibrated in cubic feet (ft.), or US gallons on a mechanical or electronic register. Some electronic meter registers can display rate-of-flow in addition to total usage. There are several types of water meter in common use. Selection is based on different flow measurement methods, the type of end user, the required flow rates, and accuracy requirements. In North America, standards for manufacturing of water meters are made by the American Water Works Association. There are two major methods of flow measurement in use, with sub-technologies within each of them. Common displacement designs include oscillating piston and nutating disk meters. Velocity-based
    6.50
    2 votes
    71
    Cuckoo clock

    Cuckoo clock

    • Dimension measured: Time
    • Subclass of: Clock
    A cuckoo clock is a clock, typically pendulum-regulated, that strikes the hours with a sound like a common cuckoo's call and typically has a mechanical cuckoo that emerges with each note. The mechanism to produce the cuckoo call was installed in almost every kind of cuckoo clock since the middle of the 18th century and has remained almost without variation until the present. The design of a cuckoo clock is now conventional. Most are made in the "traditional style" (also known as "carved") or "chalet" to hang on a wall. In the "traditional style" the wooden case is decorated with carved leaves and animals. They have an automaton of the bird that appears through a small trap door while the clock is striking. The bird is often made to move as the clock strikes, typically by means of an arm that lifts the back of the carving. There are two kinds of movements: one-day (30-hour) and eight-day clockworks. Some have musical devices, and play a tune on a Swiss music box after striking the hours and half-hours. Usually the melody sounds only at full hours in eight-day clocks and both at full and half hours in the one-day timepieces. Musical cuckoo clocks frequently have other automata which
    5.33
    3 votes
    72
    Hydrometer

    Hydrometer

    • Dimension measured: Specific gravity
    A hydrometer is an instrument used to measure the specific gravity (or relative density) of liquids; that is, the ratio of the density of the liquid to the density of water. A hydrometer is usually made of glass and consists of a cylindrical stem and a bulb weighted with mercury or lead shot to make it float upright. The liquid to be tested is poured into a tall container, often a graduated cylinder, and the hydrometer is gently lowered into the liquid until it floats freely. The point at which the surface of the liquid touches the stem of the hydrometer is noted. Hydrometers usually contain a scale inside the stem, so that the specific gravity can be read directly. A variety of scales exist, and are used depending on the context. Hydrometers may be calibrated for different uses, such as a lactometer for measuring the density (creaminess) of milk, a saccharometer for measuring the density of sugar in a liquid, or an alcoholometer for measuring higher levels of alcohol in spirits. Operation of the hydrometer is based on Archimedes' principle that a solid suspended in a fluid will be buoyed up by a force equal to the weight of the fluid displaced by the submerged part of the
    5.33
    3 votes
    73
    Peak programme meter

    Peak programme meter

    A peak programme meter (PPM) is an instrument used in professional audio for indicating the level of an audio signal. There are many different kinds of PPM. They fall into broad categories: In professional usage, where consistent level measurements are needed across an industry, audio level meters often comply with a detailed formal standard. This ensures that all meters that comply with the standard will give the same indication on a given audio signal. The principal standard for PPMs is IEC 60268-10. It describes two different quasi-PPM designs which have their roots in meters originally developed in the 1930s for the AM radio broadcasting networks of Germany (Type I) and the United Kingdom (Type II). The term Peak Programme Meter usually refers to these IEC-specified types and similar designs. PPMs were originally designed for monitoring analogue audio signals but are also now used with digital audio. PPMs do not provide effective loudness monitoring. Newer types of meter do, and there is now a push within the broadcasting industry to move away from traditional level meters such as those featured in this article to two new types: loudness meters based on EBU Tech. 3341 and
    5.33
    3 votes
    74
    Seismic source

    Seismic source

    • Subclasses: Sparker
    A seismic source is a device that generates controlled seismic energy used to perform both reflection and refraction seismic surveys. A seismic source can be simple, such as dynamite, or it can use more sophisticated technology, such as a specialized air gun. Seismic sources can provide single pulses or continuous sweeps of energy. Both types of seismic sources generate seismic waves, which travel through a medium such as water or layers of rocks. Some of the waves then reflect and refract and is recorded by receivers, such as geophones or hydrophones. Seismic sources may be used to investigate shallow subsoil structure, for engineering site characterisation, or to study deeper structures, usually in the search for petroleum or mineral deposits, or for scientific investigation. The returning signals from the sources are detected by seismic sensors (geophones or hydrophones), laid in known locations relative to the position of the source. The recorded signals are then subjected to specialist processing and interpretation to yield comprehensible data about the subsurface. A seismic source signal has the following characteristics: The generalized equation that shows all above
    5.33
    3 votes
    75
    De Prony brake

    De Prony brake

    • Dimension measured: Torque
    The de Prony Brake is a simple device invented by Gaspard de Prony to measure the torque produced by an engine. The term "brake horsepower" is one measurement of power derived from this method of measuring torque. (Power is calculated by multiplying torque times rotational speed.) Essentially the measurement is made by wrapping a cord or belt around the output shaft of the engine and measuring the force transferred to the belt through friction. The friction is increased by tightening the belt until the frequency of rotation of the shaft is reduced. In practice more engine power can then be applied until the limit of the engine is reached. In its simplest form an engine is connected to a rotating drum by means of an output shaft. A friction band is wrapped around half the drum's circumference and each end attached to a separate spring balance. A substantial pre-load is then applied to the ends of the band, so that each spring balance has an initial and identical reading. When the engine is running the frictional force between the drum and the band will increase the force reading on one balance and decrease it on the other. The difference between the two readings is used to calculate
    5.00
    3 votes
    77
    6.00
    2 votes
    78

    Ion drift meter

    An ion drift meter is a device used to measure the velocity of individual ions in the area of a spacecraft. This information can then be used to calculate the ion drift in the space surrounding the instrument as well as the strength of any electric field present, provided that the magnetic field strength has been determined using a magnetometer. The device itself works by allowing ions to pass through an opening at the front of the instrument and measuring the currents produced by the impacts of ions in different locations on a grid at the back. The trajectories of the ions can then be determined. Ion drift meters have been used on several spacecraft including Dynamics Explorer and CHAMP.
    6.00
    2 votes
    79
    Light meter

    Light meter

    A light meter is a device used to measure the amount of light. In photography, a light meter is often used to determine the proper exposure for a photograph. Typically a light meter will include a computer, either digital or analog, which allows the photographer to determine which shutter speed and f-number should be selected for an optimum exposure, given a certain lighting situation and film speed. Light meters are also used in the fields of cinematography and scenic design, in order to determine the optimum light level for a scene. They are used in the general field of lighting, where they can help to reduce the amount of waste light used in the home, light pollution outdoors, and plant growing to ensure proper light levels. The earliest type of light meters were called extinction meters and contained a numbered or lettered row of neutral density filters of increasing density. The photographer would position the meter in front of their subject and note the filter with the greatest density that still allowed incident light to pass through. The letter or number corresponding to the filter was used as an index into a chart of appropriate aperture and shutter speed combinations for
    6.00
    2 votes
    80
    RX meter

    RX meter

    An RX meter is used to measure the separate resistive and reactive components of reactive parallel Z network. The two variable frequency oscillators track each other at frequencies 100 kHz apart. The output of a 0.5-250 MHz oscillator, F1, is fed in to a bridge. When the impedance network to be measured is connected one arm across the bridge, the equivalent parallel resistance and reactance (capacitive or inductive) unbalances the bridge and the resulting voltage is fed to the mixer. The output of the 0.6-250.1 MHz oscillator F2, tracking 100 kHz above F1,is also fed to the mixer. This results in a 100 kHz difference frequency proportional in level to the bridge unbalance. The difference frequency signal is amplified by a filter amplifier combination and is applied to a null meter. When the bridge resistive and reactive controls are nulled, their respective dials accurately indicate the parallel impedance components of the network under test.
    6.00
    2 votes
    82

    Air flow meter

    An air flow meter, is a device that measures air flow, i.e. how much air is flowing through a tube. It does not measure the volume of the air passing through the tube, it measures the actual speed of the air flowing through the device in a defined time segment. Thus air flow meters are simply an application of mass flow meters for a special medium. Typically, mass air flow measurements are expressed in the units of kilograms per second (kg/s). An air flow meter is used in some automobiles to measure the quantity of air going into the internal combustion engine. All modern electronically controlled diesel engines use air flow meter, as it is the only possible means of determining the air intake for them. In the case of a petrol engine, the electronic control unit (ECU) then calculates how much fuel is needed to inject into the cylinder ports. In the diesel engine, the ECU meters the fuel through the injectors into the engines cylinders during the compression stroke. The vane (flap) type air flow meters (Bosch L-Jetronic and early Motronic EFI systems or Hitachi) actually measure air volume, whereas the later "hot wire" and "hot film" air mass meters measure speed of air flow. The
    7.00
    1 votes
    83

    LCR meter

    An LCR meter (Inductance (l), Capacitance (C), and Resistance (R)) is a piece of electronic test equipment used to measure the inductance, capacitance, and resistance of a component. In the simpler versions of this instrument the true values of these quantities are not measured; rather the impedance is measured internally and converted for display to the corresponding capacitance or inductance value. Readings will be reasonably accurate if the capacitor or inductor device under test does not have a significant resistive component of impedance. More advanced designs measure true inductance or capacitance, and also the equivalent series resistance of capacitors and the Q factor of inductive components. Usually the device under test (DUT) is subjected to an AC voltage source. The meter measures the voltage across and the current through the DUT. From the ratio of these the meter can determine the magnitude of the impedance. The phase angle between the voltage and current is also measured in more advanced instruments; in combination with the impedance, the equivalent capacitance or inductance, and resistance, of the DUT can be calculated and displayed. The meter must assume either a
    7.00
    1 votes
    84
    7.00
    1 votes
    85
    PIGA accelerometer

    PIGA accelerometer

    • Subclass of: Accelerometer
    A PIG accelerometer (Pendulous Integrating Gyroscopic Accelerometer) is a type of accelerometer that can measure acceleration and simultaneously integrates this acceleration against time to produce a speed measure as well. The PIGA's main use is in Inertial Navigation Systems (INS) for guidance of aircraft and most particularly for ballistic missile guidance. It is valued for its extremely high sensitivity and accuracy in conjunction with operation over a wide acceleration range. The PIGA is still considered the premier instrument for strategic grade missile guidance, though systems based on MEMS technology are attractive for lower performance requirements. The sensing element of a PIGA is a pendulous mass free to pivot by being mounted on a bearing. A spinning gyroscope is attached such that it would restrain the pendulum against "falling" in the direction of acceleration. The pendulous mass and its attached gyroscope are themselves mounted on a pedestal that can be rotated by an electric torque motor. The rotational axis of this pedestal is mutually orthogonal to the spin axis of the gyroscope as well as the axis that the pendulum is free to move in. The axis of rotation of this
    7.00
    1 votes
    86
    7.00
    1 votes
    87

    Integrated electronic piezoelectric accelerometer

    • Subclass of: Accelerometer
    Integrated electronic piezoelectric (IEPE) accelerometers are a class of piezoelectric accelerometers that incorporate an electronic amplifier and use a single two-pole coaxial connector for both power input and signal output. The devices are also known by proprietary names such as Integrated Circuit Piezoelectric (ICP). Compared with earlier sensor interface systems requiring a charge-sensitive preamplifier external to the sensor, the use of a single coaxial connector with integrated electronics gives IEPE devices their main advantages: small size, light weight, robustness and low cabling costs. Microphones and other vibration sensors are also made using an IEPE-compatible interface. The IEPE interface is defined in the IEEE 1451.4 standard which also includes the definition for the Transducer Electronic Data Sheet (TEDS), data from which is carried on the same interface. Some IEPE sensors are made without TEDS, using only the powering interface defined by IEEE 1451.4. Different manufacturers' implementations vary, so the manufacturer's data sheet must be consulted for each device. Power is supplied to the inner conductor of the coaxial cable from an external constant-current
    5.50
    2 votes
    89

    Stimp meter

    The Stimp Meter was invented by Edward Stimpson. It is a simple device used to measure the speed of the putting greens at a golf course. The Stimp Meter is a small ramp that a ball is run down onto a flat section of the putting surface. The device is designed so the ball rolls at a uniform speed. The stimp meter reading is the average of the number of feet that the ball rolls across the green over multiple trials. Stimpson did not intend to create a device for comparing greens at one course with greens at another, merely to assist the greenskeeper in maintaining consistency from green-to-green within the same course. See also Stimpmeter. (The U. S. Open greens rate about 12 to 14 feet)
    6.00
    1 votes
    90
    Thermometer

    Thermometer

    • Dimension measured: Temperature
    A thermometer (from the Greek θερμός, thermos, meaning "hot" and μἐτρον, metron, "measure") is a device that measures temperature or temperature gradient using a variety of different principles. A thermometer has two important elements: the temperature sensor (e.g. the bulb on a mercury thermometer) in which some physical change occurs with temperature, plus some means of converting this physical change into a numerical value (e.g. the scale on a mercury thermometer). There are many types and many uses for thermometers, as detailed below in sections of this article. While an individual thermometer is able to measure degrees of hotness, the readings on two thermometers cannot be compared unless they conform to an agreed scale. There is today an absolute thermodynamic temperature scale. Internationally agreed temperature scales are designed to approximate this closely, based on fixed points and interpolating thermometers. The most recent official temperature scale is the International Temperature Scale of 1990. It extends from 0.65 K (−272.5 °C; −458.5 °F) to approximately 1,358 K (1,085 °C; 1,985 °F). Various authors have credited the invention of the thermometer to Cornelis
    6.00
    1 votes
    91

    Variable area meter

    A variable area meter is a meter that measures fluid flow by allowing the cross sectional area of the device to vary in response to the flow, causing some measurable effect that indicates the rate. A rotameter is an example of a variable area meter.
    6.00
    1 votes
    92
    Capacitance meter

    Capacitance meter

    A capacitance meter is a piece of electronic test equipment used to measure capacitance, mainly of discrete capacitors. Depending on the sophistication of the meter, it may display the capacitance only, or it may also measure a number of other parameters such as leakage, equivalent series resistance (ESR), and inductance. For most purposes and in most cases the capacitor must be disconnected from circuit; ESR can usually be measured in circuit. Some checks can be made without a specialised instrument, particularly on aluminium electrolytic capacitors which tend to be of high capacitance and to be subject to poor leakage. A multimeter in a resistance range can detect a short-circuited capacitor (very low resistance) or one with very high leakage (high resistance, but lower than it should be; an ideal capacitor has infinite DC resistance). A crude idea of the capacitance can be derived with an analog multimeter in a high resistance range by observing the needle when first connected; current will flow to charge the capacitor and the needle will "kick" from infinite indicated resistance to a relatively low value, and then drift up to infinity. The amplitude of the kick is an indication
    5.00
    1 votes
    93

    Clarity meter

    A clarity meter is an instrument used to measure the transparency of an object.Clarity refers to the optical distinctness with which an object can be seen when viewed through plastic film/sheet,glass,etc. In the manufacture of sheeting/film,or glass the quantitative assessment of clarity is just as important as that of haze. Clarity meter has another name based on the inventor George Metyas called a metyometer. Clarity depends upon the linearity of the passage of light rays through the material. Small deflections of the light, caused by scattering centers of the material, bring about a deterioration of the image. These deflections are much smaller than those registered in haze measurements. While haze measurements depend upon wideangle scattering, clarity is determined by small-angle scattering. Wide and small angle scattering are not directly related to each other. By this, we mean that haze measurements cannot provide information about the clarity of the specimen and vice versa.
    5.00
    1 votes
    94
    Ultrasonic flow meter

    Ultrasonic flow meter

    An ultrasonic flow meter is a type of flow meter that measures the velocity of a liquid or gas (fluid) by using the principle of ultrasound. Using ultrasonic transducers, the flow meter can measure the average velocity along the path of an emitted beam of ultrasound, by averaging the difference in measured transit time between the pulses of ultrasound propagating into and against the direction of the flow. Ultrasonic flow meters are affected by the temperature, density and viscosity of the flowing medium. They are inexpensive to use and maintain because they do not use moving parts, unlike mechanical flow meters. There are three different types of ultrasonic flow meters. Transmission (or contrapropagating transit-time) flow meters can be distinguished into in-line (intrusive, wetted) and clamp-on (non-intrusive) varieties. Ultrasonic flow meters that use the Doppler shift are called Reflection or Doppler flow meters. The third type is the Open-Channel flow meter. Ultrasonic flow meters measure the difference of the transit time of ultrasonic pulses propagating in and against flow direction. This time difference is a measure for the average velocity of the fluid along the path of
    5.00
    1 votes
    95

    Zero resistance ammeter

    • Dimension measured: Electric current
    A zero resistance ammeter or "ZRA" is an instrument measuring the electric current (practically) without voltage drop across the ammeter. A standard current meter, as usually built-in in typical multimeters measures the current as a voltage drop across a shunt resistor. A usual digital 3½ digit voltmeter has a lowest current range of 200 mV, accordingly rises the voltage drop across the internal shunt resistor up to 200 mV when the current corresponds to the full range. Example: You measure a current of 100 µA in the range 200 µA of the digital voltmeter. Typically, the internal shunt resistance in this range is 1 kΩ, across which a voltage of U = R x I = 1000 Ω x 100 µA = 100 mV will drop. When measuring the current in usual electronic circuits, this voltage drop may be disregarded. For electrochemical cells, a drop of 100 mV is nearly enormous. Electrochemists therefore need zero resistance ammeters to measure the current without producing a voltage drop. To achieve this, special zero resistance ammeters, also called "active current sinks", are used. Potentiostats e.g. can be used also as ZRA, and it is very simple to do so. Connect the counter electrode terminal to the
    5.00
    1 votes
    96
    Gravimeter

    Gravimeter

    • Dimension measured: Gravitational field
    • Subclass of: Accelerometer
    A gravimeter is an instrument used in gravimetry for measuring the local gravitational field of the Earth. A gravimeter is a type of accelerometer, specialized for measuring the constant downward acceleration of gravity, which varies by about 0.5% over the surface of the Earth. Though the essential principle of design is the same as in other accelerometers, gravimeters are typically designed to be much more sensitive in order to measure very tiny fractional changes within the Earth's gravity of 1 g, caused by nearby geologic structures or the shape of the Earth and by temporal tidal variations. This sensitivity means that gravimeters are susceptible to extraneous vibrations including noise that tend to cause oscillatory accelerations. In practice this is counteracted by integral vibration isolation and signal processing. The constraints on temporal resolution are usually less for gravimeters, so that resolution can be increased by processing the output with a longer "time constant". Gravimeters display their measurements in units of gals, instead of ordinary units of acceleration. Gravimeters are used for petroleum and mineral prospecting, seismology, geodesy, geophysical surveys
    4.00
    1 votes
    97

    Blood glucose meter

    A blood glucose meter is a small, portable, battery-powered device for personal or professional blood glucose monitoring. The device is used by diabetic, who need to be able to determine and track blood glucose levels to maintain their health. A specially treated test strip containing reactive chemicals is placed inside a blood glucose meter. A drop of blood is then taken from the fingertip or an alternate site(thigh, calf, forearm, upper arm can be used on certain meters)by using a lancing device, which shoots a sterile lancet into the skin with the press of a button. The blood sample is placed on the opposite end or top of the test strip, depending on the model of blood glucose meter. The blood reacts with the chemicals in the test strip causing a small electronic pulse to be sent into the meter which then calculates the level of glucose in the blood sample and shows the result in a digital display. Different makes of meters offer a variety of functions and data management capabilities to match individual testing needs. Newer models of meters, similar to the Freestyle Flash and Precision Xtra feature one-step sampling and readout: the chemically-treated strip is placed in
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    98

    Body fat meter

    A body fat meter is a widely available tool used to measure the percentage of fat in the human body. Different meters use various methods to determine the body fat to weight ratio. In contrast with clinical tools, one relatively inexpensive type of body fat meter uses the principle of bioelectrical impedance analysis (BIA) to determine an individual's body fat percentage. To achieve this, the meter passes a small, harmless, electric current through the body and measures the resistance, then uses information on the person's weight, height, age, and sex, to calculate an approximate value for the person's body fat percentage. The calculation measures the total volume of water in the body (lean tissue and muscle contain a higher percentage of water than fat), and estimates the percentage of fat based on this information.
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    99

    Clap-o-meter

    A clap-o-meter, clapometer or applause meter is a measurement instrument that purports to measure and display the volume of clapping or applause made by an audience. It can be used to indicate the popularity of contestants and decide the result of competitions based on audience popularity. Specific implementations may or may not be based on an actual sound level meters. Clap-o-meters were a popular element in talent shows and television game shows in the 1950s and 1960s, most notably Opportunity Knocks, but have been since been supplanted by other, more sophisticated, methods of measuring audience response. One of the first appearances of a clap-o-meter was in 1956, on the British TV game show Opportunity Knocks, developed and presented by Hughie Green. The clap-o-meter itself was a wooden box labelled "Audience Reaction Indicator". The prop is now part of the collection of the National Media Museum, in Bradford. Clap-o-meters were used in many other TV shows and at live events. In 1989, Green unsuccessfully attempted to sue the New Zealand Broadcasting Corporation for copyright infringement over a similar programme. The clap-o-meter was one of the distinctive features of the
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    100
    Ekman current meter

    Ekman current meter

    The Ekman current meter is a mechanical flowmeter invented by Vagn Walfrid Ekman a Swedish oceanographer, in 1903. It comprises a propeller with a mechanism to record the number of revolutions, a compass and a recorder with which to record the direction, and a vane that orients the instrument so the propellor faces the current. It is mounted on a free-swinging vertical axis suspended from a wire and has a weight attached below. The balanced propellor, with four to eight blades, rotates inside a protective ring. The position of a lever controls the propeller. In down position the propellor is stopped and the instrument is lowered, after which reaching the desired depth a weight called a messenger is dropped to move the lever into the middle position which allows the propeller to turn freely. When the measurement has been taken another weight is dropped to push the level to its highest position at which the propeller is again stopped. The propeller revolutions are counted via a simple mechanism that gears down the revolutions and counts them on an indicator dial. The direction is indicated by a device connected to the directional vane that drops a small metal ball about every 100
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    101
    Goddard High Resolution Spectrograph

    Goddard High Resolution Spectrograph

    The Goddard High Resolution Spectrograph (GHRS or HRS) was a spectrograph installed on the Hubble Space Telescope. It was replaced by the Near Infrared Camera and Multi-Object Spectrometer (NICMOS) in 1997. A technical description of the construction and operation of the GHRS can be found in NASA technical report CP-2244.
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    102
    GPS navigation device

    GPS navigation device

    A GPS navigation device is any device that receives Global Positioning System (GPS) signals for the purpose of determining the device's current location on Earth. GPS devices provide latitude and longitude information, and some may also calculate altitude, although this is not considered sufficiently accurate or continuously available enough (due to the possibility of signal blockage and other factors) to rely on exclusively to pilot aircraft. GPS devices are used in military, aviation, marine and consumer product applications. GPS devices may also have additional capabilities such as: In other words, all GPS devices can answer the question "Where am I?", and may also be able to answer: Consumer GPS navigation devices include: Dedicated devices have various degrees of mobility. Hand-held, outdoor, or sport receivers have replaceable batteries that can run them for several hours, making them suitable for hiking, bicycle touring and other activities far from an electric power source. Their screens are small, and some do not show color, in part to save power. Cases are rugged and some are water resistant. Other receivers, often called mobile are intended primarily for use in a car,
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    103

    Moisture meter

    Moisture meters are used to measure the percentage of water in a given substance. This information can be used to determine if the material is ready for use, unexpectedly wet or dry, or otherwise in need of further inspection. Wood and paper products are very sensitive to their moisture content. Physical properties are strongly affected by moisture content. Dimensioning also changes with moisture content. Newly-cut logs can have a moisture content (MC) of 80% or more, depending on species. Since wood shrinks, and can also split, twist or otherwise change shape as it dries, most wood is dried before being used. This is most often done using a kiln, but may use the air drying method, which is much slower. In most parts of the United States, the minimum moisture content that can be generally obtained in air drying is about 12 to 15 percent. Most air-dried material is usually closer to 20 percent moisture content when used. In-kiln drying is usually monitored by some type of moisture meter. Moisture meters are used to measure the amount of water in the wood so that the woodworker can determine if it is suitable for the intended purpose. Building inspectors and many more, carpenters,
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    104
    Ramp meter

    Ramp meter

    A ramp meter, ramp signal or metering light is a device, usually a basic traffic light or a two-section signal (red and green only, no yellow) light together with a signal controller, that regulates the flow of traffic entering freeways according to current traffic conditions. It is the use of traffic signals at freeway on-ramps to manage the rate of automobiles entering the freeway. Ramp metering systems have proved to be successful in decreasing traffic congestion and improving driver safety. Ramp meters are claimed to reduce congestion (increase speed and volume) on freeways by reducing demand and by breaking up platoons of cars. Two variations of demand reduction are commonly cited; one being access rate, the other diversion. Ramp meters are installed to restrict the total flow entering the freeway, temporarily storing it on the ramps, a process called "access rate reduction." In this way, the traffic flow does not exceed the freeway's capacity. Another rationale for installing ramp meters is the argument that they prevent congestion and break up "platoons" of cars. A platoon is a group of vehicles travelling in proximity, such as a green wave released by an arterial traffic
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    105
    Selenium meter

    Selenium meter

    A selenium meter is a light-measuring instrument based on the photoelectric properties of selenium. The most common use of such light meters is measuring the exposure value for photography. The electric part of such a meter is an electromagnetic measuring instrument which is connected to the anode and cathode of a selenium photo cell that produces more or less electric power when exposed to more or less light. The optical part of such a meter is a window in front of the photo cell's light-sensitive side. The window's surface is usually structured like a honeycomb made of convex lenses. This type of window helps to bundle the light coming from the direction in which the photo cell is pointed. The mechanical part of a selenium meter is an analog calculator which accepts exposure value and film speed as input parameters for showing the possible aperture and shutter-speed combinations for correct exposure. The simplest type of match-needle selenium meter shows a clockhand on the meter's scale. This can be moved by turning one slice of the analog calculator. When the clockhand matches the instrument's needle the EV-value is set right on the calculator. The picture on the right shows the
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    106
    Sphygmomanometer

    Sphygmomanometer

    • Dimension measured: Blood pressure
    A sphygmomanometer ( /ˌsfɪɡmoʊməˈnɒmɨtər/ SFIG-moh-mə-NOM-i-tər) or blood pressure meter (also referred to as a sphygmometer) is a device used to measure blood pressure, composed of an inflatable cuff to restrict blood flow, and a mercury or mechanical manometer to measure the pressure. It is always used in conjunction with a means to determine at what pressure blood flow is just starting, and at what pressure it is unimpeded. Manual sphygmomanometers are used in conjunction with a stethoscope. The word comes from the Greek sphygmós (pulse), plus the scientific term manometer (pressure meter). The device was invented by Samuel Siegfried Karl Ritter von Basch in 1881. Scipione Riva-Rocci introduced a more easily used version in 1896. In 1901, Harvey Cushing modernized the device and popularized it within the medical community. A sphygmomanometer consists of an inflatable cuff, a measuring unit (the mercury manometer, or aneroid gauge), and a mechanism for inflation which may be a manually operated bulb and valve or a pump operated electrically. The usual unit of measurement of blood pressure is millimeters of mercury (mmHg) as measured directly by a manual sphygmomanometer. There
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