What problems do we encounter in using loop resistance testers?

The loop resistance tester(Contact Resistance Tester,circuit resistance tester) is an instrument that is used very frequently in our power industry, but in fact, this instrument will encounter some problems during use, how do we solve these problems?

According to the conventional design principle of loop resistance testers (contact resistance tester,circuit resistance tester) found in the field test, they will have a common problem: when the tester voltage wiring loop has poor contact or open circuit, the tester will display a value, and the following situations will occur about the value:

1, the voltage loop is open, the test site has no strong electric field interference, in this case, because the differential mode voltage of the amplifier input is basically 0, so the test value displayed by the instrument is close to 0, if the tester has enough field test experience, We can judge from it that the instrument voltage loop test line is abnormal, and after the instrument voltage loop test line is abnormally discharged, we can obtain the final correct test result;

2, the voltage loop contact is poor, in most cases the circuit breaker terminal in the long-term operation of the rear end of the outer surface of the sub-row will produce oxide film or oil film, when the loop resistance meter voltage test clamp clamp to such a terminal block may produce poor contact, both the voltage test line clamp itself to produce a certain contact resistance, the contact resistance value to the voltage sampling circuit internal resistance value when the equivalent will have a serious impact on the test results.       

3. The voltage loop is open circuit or poor contact, and the test site has strong electromagnetic interference, such as the busbar is charged, at this time, the charged bus bar passes through the capacitance of the air as the medium, interfering with the two voltage test lines of the tester, and the differential mode voltage appears at both ends of the voltage collection line of the loop tester due to the effect of interference.