Research on Weak Signal Measurement System for Electric-Field Measurement of Transformer Oil Based on Kerr Effect

As the Kerr constant of liquid medium is small, it is difficult to accurately detect the weak signals which from electric field measurement of transformer oil based on Kerr effect. To improve the accuracy of weak signal measurement, a weak signal measurement system was designed in this paper, which consists of signal channel module, reference channel module and phase sensitive detector module. The structure parameters of the lock-in amplifier processing system were designed carefully, and the measurement performance of the designed weak signal measurement system were tested. The test result showed that the weak signal measurement system can measure the low SNR weak signals accurately, and the measuring error were less than 2μV when there was 1mV signal noise or not. The weak signal measurement system possesses high linearity and accuracy.