The multimeter is shorted, the multimeter does not return to zero
1. Release the test lead, and observe whether the pointer can return to zero at the initial position on the left. If it cannot be reset to zero, use a fingernail to insert the Bakelite adjustment eccentric rod at the root of the adjustment pointer to reset it to zero. If there is no response to the adjustment, the small internal rod is broken. To reset to zero, put the meter on the table and hold it on both sides of the table and shake it left and right to observe whether the needle is obstructed from the leftmost to the rightmost. Obstructions indicate that the hands are scratching the dial or glass. Take it apart for repair. No barriers, go to the next step.
2. Adjust the zeroing knob to the right to the end, which is the maximum zeroing correction. The red test lead touches the metal seat of the black test lead socket, and the black test lead touches the metal seat of the red test lead, which is equivalent to the parallel connection of the two test leads, and can be reset to zero, indicating that the test leads have poor contact and should be checked and ruled out. Can not return to zero, go to the next step
3. Remove the cover of the battery box at the bottom, take out the 1.5 volt battery, and put the multimeter in the DC voltage 2.5 volt range. Check whether the battery has 1.5 volts, if it is not enough, replace it. If the voltage is sufficient, observe whether there is oxidation and rust on the positive and negative shrapnel of the battery box, and if so, remove it. No rust, adjust the shrapnel to enhance the contact with the battery, and install the battery. See if it can be reset to zero. Can not be zeroed, the next step.
4. Disassemble the meter box and observe the center contact piece of the zero-returning wire wound potentiometer, whether there is any bad contact or the resistance wire of the potentiometer is broken. no problem, next step
5. Check the contact condition of the ohmic position of the shift switch, and observe whether the switch is in poor contact. No problem, go to the next step.
6. Observe whether the small wirewound resistor in the ohm x1 range is burnt.
If the first five steps are all normal, the problem is the sixth step. Usually someone accidentally sets the ohm scale to measure the voltage and burns out the internal small wirewound resistor, resulting in failure to return to zero. Accurately match the resistor with the same resistance value, and the fault is eliminated.
