| 摘要 |
<p>The mains power supply can be single or three-phase. An auxiliary voltage source (2) is inserted between earth (M) and the tested object (4) through a coupling component (7) and a measurement resistor (9). The frequeny of the auxiliary voltage (U2) source (2) is an integral submultiple of the mains frequency (f1). A voltage representing current (I) in the measurement circuit (2, 4, 9, M) and a reference voltage collected from it are applied to an evaluation circuit (12-19). This circuit contains a phase sensitive demodulator (15) controlled by the reference voltage. Its output voltage is a measure for the resistance (5) between the object (4) and earth (M).</p> |
