a) The battery voltage is insufficient. The battery voltage is too low, causing the circuit to not work normally, so the measured reading is inaccurate.

b) The test wire connection is incorrect. Wrongly connect the "l", "g", "e" three-terminal wiring, the insulation resistance tester or "g", "l" wiring "g", "e" wiring is connected to the two ends of the tested product .

c) The "g" terminal is not connected. The test product has errors caused by current leakage due to contamination, humidity and other factors, resulting in inaccurate testing. At this time, the "g" terminal must be connected to prevent leakage current from causing errors.

d) Excessive interference. If the product under test is subject to excessive electromagnetic interference from the environment, the meter reading will jump. Or the pointer is shaking. Cause inaccurate readings.

e) Human reading errors. When measuring with a pointer type insulation resistance tester, the displayed value is inaccurate due to artificial viewing angle errors or scale errors.

f) Insulation resistance tester instrument error. The error of the meter itself is too large and needs to be re-calibrated.