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单词 voltmeter
释义
voltmeter

Physics
  • An instrument used to measure voltage. Moving-coil instruments are widely used for this purpose; generally a galvanometer is used in series with a resistor of high values (sometimes called a multiplier). To measure an alternating potential difference a rectifier must be included in the circuit. A moving-iron instrument can be used for either d.c. or a.c. without a rectifier. Cathode-ray oscilloscopes are also used as voltmeters. The electronic digital voltmeter displays the value of the voltage in digits. The input is repeatedly sampled by the voltmeter and the instantaneous values are displayed.


Electronics and Electrical Engineering
  • A device that measures voltage. Voltmeters in common use include digital voltmeters, cathode-ray oscilloscopes, and d.c. instruments (such as permanent-magnet moving-coil instruments).

    In order to provide the minimum disturbance in the circuit containing the voltage to be measured, voltmeters are required to pass very little current and therefore require a very high input impedance. Digital voltmeters, cathode-ray oscilloscopes, and the now little used valve voltmeter comply with this requirement. A large series resistance however is required in the case of the moving-coil voltmeter and the electrostatic voltmeter in order to increase their input impedances. The electrostatic voltmeter is a voltmeter based upon the principle of operation of a quadrant electrometer or other type of electrometer.


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