AC milliohm meter based on complex programmable logic device, and measurement method therefor

Abstract

The invention discloses an AC milliohm meter based on a complex programmable logic device (CPLD), and a measurement method therefor. The output of the CPLD is connected in series with a D / A converter and a second-order filter in turn and then forms a 1kHz voltage signal source; the voltage signal source is connected with a resistor to divide voltage; a feedback closed ring is connected in series between the voltage signal source and a tested resistor; the feedback closed ring consists of an error amplifier, a difference amplifier and a measurement range resistor and is connected with the CPLD; voltage at two ends of the tested resistor is connected with a band-pass amplifier through an isolating capacitor; the output of the band-pass amplifier is connected with a lock-in amplifier and a 20mV clamp control circuit respectively; the output of the 20mV clamp control circuit is connected with the CPLD and the resistor; the output of the lock-in amplifier is connected with an integral-type A / D converter; the lock-in amplifier and the integral-type A / D converter are connected with the CPLD respectively; and an MCU is connected between the CPLD and a display / separation module. The AC milliohm meter has test current less than 100 mA, has open circuit voltage within 20 mV, can test large-capacitance equivalent series resistance parameters, increases system integration level, and can improve the measurement resolution and signal-to-noise ratio of AC voltage.

Description

technical field [0001] The invention relates to a measuring instrument for testing various milliohm resistances, which can measure the contact resistance of electromechanical components, the internal resistance of batteries and the equivalent resistance in series of supercapacitors. Background technique [0002] At present, the DC test method is basically used in the field of low-resistance testing. The resolution of voltage measurement is difficult to exceed 1μV. To measure and distinguish a resistance of 1μΩ, the excitation current must reach 1A. The open circuit voltage is high and the anti-interference ability is weak. It does not meet the requirements of the national standard GB5095 and GBT351 (the national standard requires the test current to be less than 100mA, and the open circuit voltage is limited to within 20mV) for contact resistance detection of electronic equipment. [0003] Based on Complex Programmable Logic Device (CPLD), it is a digital integrated circuit ...

AI Technical Summary

Problems solved by technology

[0002] At present, the DC test method is basically used in the field of low-resistance testing. The resolution of voltage measurement is difficult to exceed 1μV. To measure and distinguish a resistance of 1μΩ, the excitation current must reach 1A. The open circuit voltage is high and the anti-interference ability is weak. Does not meet the national standard GB5095 and GBT351 (the national standard requires the test current to be less than 100mA, and the open circuit voltage is limited to within 20mV) for contact resistance detection requirements of electronic equipment

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