By hvhipot 
Common faults and solutions of DC resistance tester are as follows:
1. The DC resistance tester tests normally, but the resistance value cannot be measured.
There are generally two reasons for the phenomenon that the value cannot be measured: 1. The switching power supply is broken and there is no current output; 2. The set value exceeds the device range, and the program cannot recognize the command.
If the power supply is damaged, just replace the power supply. If it is over-range, restart the instrument and select the resistance or current within the range for measurement.
2. Fuzzy screen appears during the test of the DC resistance tester.
Fuzzy screen of the direct resistance meter is most likely due to poor contact of the internal cable. Turn off and check whether the cable is loose. Reinforce the cable to solve the problem.
Another possibility is that the screen display is abnormal due to electromagnetic interference. If this is the reason, just contact the manufacturer and add a filter capacitor.
3. When the DC resistance tester is turned on, the insurance will be burned out.
There are two situations in which the insurance burned when starting up: This is the case with the direct resistance meter of 5A~10A. Generally speaking, the built-in transformer is burned out by the high voltage, which makes the instrument unable to use normally; the direct resistance meter with current above 20A has this situation. Situation, usually there is a problem with the switching power supply. In case of burning insurance, just replace the transformer or switching power supply in time and it can be used normally. When the equipment is repaired, a professional engineer must disassemble the equipment. If the repair conditions are not available on site, it must be returned to the factory for repair.
In addition to the quality problems of the DC resistance tester itself, unreasonable operation methods and storage methods can also cause equipment damage. During use, do not touch the LED screen with high-temperature objects, and check whether the input interface fixture is normal before testing. In addition, keeping the equipment dry and clean is also an effective way to extend the service life. For the special requirements of accurate measurement of testing equipment, it is best to calibrate the equipment once a year to ensure the accuracy and stability of the measured values.