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Analog multimeter Digital multimeter. A multimeter (also known as a volt-ohm-milliammeter, volt-ohmmeter or VOM) [1] is a measuring instrument that can measure multiple electrical properties. [2] [3] A typical multimeter can measure voltage, resistance, and current, [4] in which case can be used as a voltmeter, ohmmeter, and ammeter.
Clamp meters are used by electricians, sometimes with the clamp incorporated into a general purpose multimeter. It is simple to measure very high currents (hundreds of amperes) with the appropriate current transformer. Accurate measurement of low currents (a few milliamperes) with a current transformer clamp is more difficult.
Digital voltmeters give a numerical display of voltage by use of an analog-to-digital converter. Voltmeters are made in a wide range of styles, some separately powered (e.g. by battery), and others powered by the measured voltage source itself. Instruments permanently mounted in a panel are used to monitor generators or other fixed apparatus.
In a similar way, accurate AC/DC non-contact ammeters have been constructed using Hall effect magnetic field sensors. A portable hand-held clamp-on ammeter is a common tool for maintenance of industrial and commercial electrical equipment, which is temporarily clipped over a wire to measure current. Some recent types have a parallel pair of ...
The multimeter is often called simply an AVO, because the company logo carries the first letters of 'amps', 'volts' and 'ohms'. The design concept is due to the Post Office engineer Donald Macadie, who at the time of the introduction of the original AVOmeter in 1923 was a senior officer in the Post Office Factories Department in London.
Diagram showing positive tip polarity on the left and negative tip polarity on the right. To read diagram: The center positive drawing on the left indicates that the center (also known as the tip) of the output plug is positive (+) and the barrel (ring) of the output plug is negative (−).
IEC 62156 Digital video recording with video compression 12,65 mm type D-9 component format 525/60 and 625/50 (Digital S) IEC TR 62157 Cylindrical machined carbon electrodes – Nominal dimensions IEC PAS 62162 Field-induced charged-device model test method for electrostatic discharge withstand thresholds of microelectronic components