The accuracy self-check of the direct current bridge tester needs to be achieved through "standard comparison + function verification", the core of which is to calibrate the key range with the standard resistance box, and at the same time check the hardware status, the specific operation is as follows:

First, make self-inspection preparations, prepare standard resistance boxes that have been calibrated (with a range covering the common levels of the tester), original four-end test leads, and operate in an environment without strong electromagnetic fields, with a temperature of 20 ± 5 ℃ and humidity ≤ 70%. The tester is powered on and preheated for 15-30 minutes.

Then perform the core calibration of the range, segmented by the range of the tester (such as 0-200mΩ, 0-20kΩ), select 3 key values in each segment (such as 10mΩ, 100mΩ, 200mΩ for the low resistance range). After the four-wire connection, set the corresponding current of the tester (use a large current for low resistance, such as 10A; use a small current for high resistance, such as 100mA), adjust the resistance box to the target value, measure twice and take the average value, calculate the relative error, if ≤ the instrument's rated accuracy (such as ±0.5%), it is qualified.

Then perform auxiliary function verification, measure the output current of the tester with a clamp meter, and a deviation ≤ ±2% is normal; short-circuit the test terminal, the displayed value should ≤ 10mΩ; open circuit when the displayed value ≥ 100MΩ, and check the wiring or internal fault if abnormal.

The last record of self-inspection data, if the error of a certain gear exceeds the standard, the terminal can be cleaned, the line can be replaced for re-measurement, and if it is still abnormal, it can be sent for repair; functional verification faults need to be directly contacted with professional personnel for maintenance, and it is forbidden to use it with faults.