The multimeter rod is short circuited, and the multimeter does not return to zero
There are multiple reasons, from outside to inside, from simple to complex, step by step search.
1. Release the pen and observe if the pointer can return to zero at the starting position on the left. If it cannot be reset to zero, insert a nail into the electric wood adjustment eccentric rod at the root of the adjustment pointer to reset to zero. The adjustment has no response, and the internal small rod has broken. Can be reset to zero, place the meter on both sides of the tabletop and hold it, and shake it left and right against the tabletop. Observe if there is any obstruction halfway from the left to the right of the watch needle. If there is an obstruction, it indicates that the pointer is scraping the dial or glass. Disassemble and repair. Accessible, take the next step.
2. Adjust the zero knob to the bottom right, which is the maximum zero correction amount. The red pen touches the metal seat of the black pen socket, while the black pen touches the metal seat of the red pen, which is equivalent to two parallel probes that can be reset to zero. This indicates that there is a poor contact between the pens, which needs to be checked and eliminated. Cannot return to zero, proceed to the next step
3. Remove the bottom battery box cover, remove the 1.5V battery, and place the multimeter in the DC voltage range of 2.5V. Measure if the battery has 1.5 volts, if not enough, replace it. If the voltage is sufficient, observe whether there is oxidation and rust on the positive and negative spring plates of the battery box. If there is, remove it. No rust, adjust the shrapnel to enhance contact with the battery, and install the battery. See if it can be reset to zero. Cannot return to zero, next step.
4. Open the meter box and observe if the zero wire is wound around the center contact of the potentiometer for poor contact or if the resistance wire of the potentiometer is broken. No problem, next step
5. Check the contact condition of the ohmic gear position of the gear shift switch and observe for poor contact on the switch. No problem, take the next step.
6. Observe the small winding resistance of Ohm x1 gear for any burning.
If the first five steps of inspection are all normal, the problem is the sixth step. Usually, some people do not pay attention and mistakenly use the ohm range to measure voltage, burning out the internal small wire winding resistance, causing it to not return to zero. By accurately matching a resistor with the same resistance value, the fault is eliminated.
