The DC low resistance tester adopts the four terminal measurement method and is a specialized instrument for measuring low DC resistance. The HY2512 series DC low resistance tester developed and produced by Haoyi has high precision, high resolution, and high-speed measurement characteristics, with a maximum accuracy of 0.05% and a minimum resolution of 1 μ Ω.
- What are 4-terminal measurement and 2-terminal measurement
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The above diagram is an abstract schematic of the four terminal measurement and two terminal measurement. The DC resistance tester can be equivalent to having one voltmeter inside to measure the voltage drop across the tested component, and one ammeter to measure the current flowing through the tested component. The final measured voltage divided by the current is the impedance of the tested component.
When using a 4-terminal connection for measurement, the detection terminal of the voltmeter directly contacts the measured component. Due to the very high input impedance of the voltmeter, the voltage measured by the voltmeter is actually the voltage drop across the measured component. The final measured voltage divided by the current is the true impedance of the measured component, thus eliminating the influence of resistance on the measurement line.
When using a two terminal connection for measurement, the voltage drop caused by the resistance on the measuring line will be detected by the voltmeter, so the final result includes the resistance on the measuring line.
- When DC low resistance is used for automated testing, how should it be wired?
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The instrument has a total of four pairs of test terminals: HD (current drive high End), LD (current drive low end), HS (Voltage sampling high end), and LS (voltage sampling low End). When measuring, HD, HS, LD, LS should be connected to the leads of the component under test to form a complete four-terminal test, so as to reduce the influence of the leads and connection points on the test results. Especially when testing low-resistance components, HS and LS should be connected to the lead terminals of the components to prevent the lead resistance from adding to the impedance under test. The principle of connection is that the voltage detected by HS and LS should be the actual voltage existing on the device under test.
If the contact point and lead resistance Rlead is much smaller than the measured impedance (for example: Rlead<zx 1000, the error influence is required to be less than 0.1%), hd, hs, ld, ls can be connected together first, and then connected to both ends of the measured device (measured at both ends).