Device and method for suppressing earth leakage and common-mode interference of cable of differential resistance sensor

Abstract

The invention relates to a device and method for suppressing earth leakage and common-mode interference of a cable of a differential resistance sensor. The device comprises a controllable constant current differential excitation circuit, an error amplification circuit and a differential measurement circuit which are connected in sequence, the controllable constant current differential excitation circuit is an excitation and differential measurement circuit with high impedance characteristic relative to the ground, so that influence of residual ground noise interference is presented as common-mode interference; residual common-mode interference is removed by the high common-mode rejection ratio characteristic of the differential measurement circuit; and the voltage between the potential value of the common end of the two resistor arms of the differential resistance sensor and the ground potential is forced to be almost zero through the error amplification circuit. Thus, the current flowing through the earth leakage impedance of the cable core is almost zero, the leakage current and the noise interference current are greatly reduced, the current flowing through the two resistor armsof the differential resistance sensor is ensured to be equal to each other to the greatest extent, and the accuracy of a resistance ratio measurement value is ensured.

Description

technical field [0001] The invention is used in the fields of safety monitoring of the stability of public facilities such as reservoir dams, bridges, and road slopes, as well as geological disaster monitoring, and specifically relates to a device and method for actively suppressing ground leakage and common-mode interference of differential resistance sensor cables . Background technique [0002] Usually, the five-wire measurement method is used to measure the parameters of differential resistance sensors, such as figure 1 The schematic diagram of the conventional five-wire measurement is shown. Among them, Rs1 and Rs2 are the two resistance arms of the differential resistance sensor, Iex is the excitation current, L-a, L-b, L-c, L-d, L-e are the cable core wires, Ra, Rb, Rc, Rd, Re are the internal resistance of the cable core wires, Za, Zb, Zc, Zd, Ze are the earth leakage impedance of the cable core wire, Vb, Vc, Vd are the voltage measurement terminals, Zg is the impe...

AI Technical Summary

Problems solved by technology

[0004] In order to avoid the increase of leakage current caused by the decrease of the cable core wire to ground leakage resistance after the cable is damp, and the increase of interference current caused by the distributed capacitive coupling of the cable when there is strong ground noise, affecting the resistance comparison measurement of the differential resistance sensor Value accuracy and other issues, the present invention provides a hardware design - a device for suppressing differential resistance sensor cables to ground leakage and common mode interference, controllable current constant current differential excitation circuit excitation and differential measurement of high impedance relative to the ground The circuit makes the influence of residual earth noise interference appear as common-mode interference characteristics, and the residual common-mode interference is removed by the high common-mode rejection ratio characteristics of the differential measurement circuit, and the common terminal potential of the two resistance arms of the differential resistance sensor is forced by the error amplifier circuit The value is equal to the earth potential value, so as to ensure that the leakage current of the cable core wire to the ground is almost zero, and at the same time greatly reduce the leakage current of other core wires to the ground and the noise interference current, and ensure that the current flowing through the two resistance arms of the differential resistance sensor is maximized. The current is equal to ensure the accuracy of the resistance ratio measurement

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