Two-port testing method of alternating current milliohm meter

Abstract

The invention discloses a two-port testing method of an alternating current milliohm meter, which is used for measuring the resistance and comprises the following steps: firstly, one end of a coaxial-cable is connected with an excitation source circuit, a shielding layer of the coaxial-cable is connected with an earth wire of the excitation source circuit; secondly, one end of the other coaxial-cable is connected with a sampling circuit, a shielding layer of the coaxial-cable is connected with the negative terminal input of the sampling circuit, an inner core wire of the coaxial-cable is connected with the positive terminal input of the sampling circuit; thirdly, the other ends of the two coaxial-cables are respectively connected with two ends of a tested piece; fourthly, excitation current flows through inner cores of the coaxial-cables and then flows through the tested piece, at last flows back to an excitation source through the shielding layers of the coaxial-cables; fifthly, current of the sampling circuit flows through the inner cores of the coaxial-cables, and then flows through the tested piece, at last flows back to the sampling circuit through the shielding layers of the coaxial-cables. The invention reduces the area of the excitation circuit and the sampling circuit, effectively lowers the noise coupling, inhibits the magnetic field coupling interference, obviously improves the interference free performance, and increases the testing accuracy.

Description

technical field [0001] The invention relates to a testing method of an AC milliohm meter, which is used for measuring contact resistance, storage battery internal resistance and supercapacitor equivalent series resistance. Background technique [0002] The test method of the AC milliohm meter is to use a 1kHz AC signal as an excitation signal, apply it to the device under test, and sample its AC voltage value at the same time, and calculate the resistance value according to Ohm's law. Since the measurement resolution of the AC voltage can improve the signal-to-noise ratio by using a band-pass amplifier, a lock-in amplifier, and an integrated integral A / D converter, the final voltage can resolve signals up to 10nV or higher. To measure a resistance of 1μΩ, the excitation current is only 10mA, and the open circuit voltage is easily limited within 20mV, which can fully meet the national standard requirements for contact resistance of electronic components (GB5095 and GBT351 req...

AI Technical Summary

Problems solved by technology

[0004] 1. It is impossible to achieve high accuracy and test stability under a small test current

[0005] 2. The ability to suppress magnetic field interference is poor, especially when the test current is small and the test line is longer, the interference is more obvious

[0006] 3. The area of ​​the test loop is large, the coupling inductance and parasitic inductance are relatively large, and it is easy to be interfered, especially under the condition of small test current or long test line, the test accuracy is not easy to improve due to interference

[0008] When performing low-resistance testing, the resistance of the test line and contact resistance will seriously affect the test accuracy and test stability

Images