Clamp meter

Ranked #19 on the list Best Measuring Instrument of All Time

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About Clamp meter

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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

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