Dielectric response micro-current measuring circuit with active error suppression function

Dielectric response test is a non-destructive and highly sensitive tool for insulation characterization, it requires a high-precision micro-current measurement circuit, which can meet the requirements of field with complex electromagnetic interference and large temperature change. Ultra low bias current amplifiers are commonly used in micro-current measurements to complete I-V transformation. However, bias and offset currents are very susceptible to temperature. The test process is easily disturbed by external power frequency and electromagnetic noise in the form of radiation. In this paper, the principle of feedback resistance method in micro current test is analyses. At the same time, this paper analyses the effect of the error caused by the amplifier and temperature. On the basis of error analysis, a novel current test topology is proposed, which can effectively suppress the power frequency interference and temperature drift of chip. Through the introduction of differential architecture, the purpose of high accuracy current measurement under limited component accuracy is achieved. Experimental results show that test results of the proposed circuit having high linearity in the current range of 10
^-7
A to 10
^-10
A Additional current testing results using dielectric response test system which contains proposed circuit are also given, which reveals the stability of the designed micro-current measurement device.