A Microcurrent Measuring Circuit for Dielectric Response Test

Abstract

The invention discloses a micro-current measuring circuit for dielectric response tests; the micro-current measuring circuit comprises a logarithm operation unit, a linear optical coupler unit, an index operation unit, and a signal secondary amplification unit connected in sequence; the logarithm operation unit comprises an ultra low bias current amplifier and a negative feedback element; the linear optical coupler unit comprises a linear optical coupler chip and a negative feedback circuit; the index operation unit comprises a high speed operation amplifier and a photosensitive diode; the micro-current measuring circuit has no feedback resistor, so the measuring result cannot be affected by a resistance temperature coefficient, thus providing high temperature drift influence inhibition ability, and the temperature coefficient can reach 100ppm / C.

Description

technical field [0001] The invention relates to the technical field of dielectric response testing of high-voltage electrical equipment, in particular to a microcurrent measurement circuit for dielectric response testing. Background technique [0002] In the field of dielectric response testing and high-voltage industrial applications, micro-current amplifier circuits are often used, and current amplifiers are required to have high precision. Currently on the market, I-V conversion amplifiers or sampling resistors are often used to amplify weak currents. [0003] For example, an I-V second-order differential measurement method and device disclosed in CN102323486A. The device includes a DC signal source, a function generator, an AC-DC adder with a voltage dividing function, a preamplifier, a lock-in amplifier and an environmental condition control system; The DC bias voltage superimposes and acts on the test sample together. The signal containing the test sample information...

AI Technical Summary

Problems solved by technology

But its disadvantage is: but because the feedback resistor with large resistance is required for current-voltage conversion, its output voltage signal will be interfered by power frequency radiation and high frequency radiation

The above two requirements indicate that the existing current amplification circuit or current testing method cannot well meet the actual needs

[0005] At the same time, another current measurement method based on Rogowski coils cannot measure current signals with higher or lower frequency ranges

This measurement method has a high isolation voltage, but it can only measure power frequency signals

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