Voltmetr

Voltmetr, or voltmeter in English, is an electrical instrument used to measure the potential difference between two points in an electric circuit. It is connected in parallel with the circuit element across which the voltage is to be measured, so as to draw only a small current from the circuit. Voltmeters are designed with high input impedance to minimize loading effects on the circuit under test.

Two main types exist: analog voltmeters and digital voltmeters. Analog voltmeters typically use a moving-coil galvanometer and a series resistance to convert voltage into a mechanical deflection on a calibrated scale. Digital voltmeters use a high-impedance input stage, an analog-to-digital converter, and a numeric display. They are commonly found as part of digital multimeters or as handheld standalone devices.

AC voltmeters can indicate alternating voltage; some meters measure true RMS values, while simpler devices use average-responding conversions. Modern meters offer multiple voltage ranges, from fractions of a volt to several kilovolts, selectable automatically or manually.

Proper use requires attention to safety and instrumentation limits. Use equipment rated for the expected voltage and category, observe probe insulation and clearance, and employ fusing or isolation as needed.

Origin: the volt is named after Alessandro Volta, and voltmeters have evolved from early galvanometer-based instruments to modern digital designs. See also: multimeter, oscilloscope.