| 摘要 |
PURPOSE:To eliminate the influence of capacitive components and also perfectly eliminate the influence of ground potential by making the test frequency half the source frequency and automatically selecting earth lines. CONSTITUTION:The source voltage from a power supply plug socket L is supplied via an auxiliary power transformer T to an auxiliary power source D for electronic circuits and is also supplied to a flip-flop F, from which the square wave output of the frequency half the source frequency is supplied via a resistance r3 to an earth object Q to be tested and a test bar H. An inverting amplifier A1 measures ground potential drop R.ig, and supplies the same to an indicating meter M by way of a polarity inversion switch S which is synchronously inversion-controlled by the output of the flip-flop F. On the other hand, source voltage is supplied to a comparing amplifier A2, and earth lines are automatically selected by a select switch P. Thereby, the influence of the ground potential and the influence of the drift of the operational amplifier are perfectly removed and high accuracy is obtained. |
