chapter  18

Meter Voltage Measurement

WithAlessandro Ferrero

Instruments for the measurement of electric voltage are called voltmeters. Correct insertion of a voltmeter requires the connection of its terminals to the points of an electric circuit across which the voltage has to be measured, as shown in Figure 18.1. To a first approximation, the electric equivalent circuit of a voltmeter can be represented by resistive impedance Z v (or a pure resistance R v for dc voltmeters). This means that any voltmeter, once connected to an electric circuit, draws a current I v given by