How to prevent the pointer of a multimeter from bending and the head from burning out
When using a multimeter, improper operation may bend the pointer, and in severe cases, the meter head may be burned.
To prevent such accidents from occurring, the following precautions should be taken when using a multimeter:
1) Before measuring, estimate the size of the measured object and turn the range switch to the appropriate range.
If you are unsure of the measured size, you can first set the range to the maximum range and then slowly move closer to the appropriate range.
Note that when measuring large objects with a small range, it is highly possible to bend the pointer.
2) When measuring resistance, the tested circuit must be disconnected from the power supply.
3) When testing high voltage or high current, it is prohibited to rotate the range switch. To prevent arcing of the contacts and damage to the switch.
4) When measuring the Electrolytic capacitor, first discharge it after short circuit, and then measure it.
5) When using a multimeter incorrectly, the meter head may be burned.
Preventive measures: Two silicon diodes are connected in parallel at the positive and negative ends of the meter head for protection (one in forward parallel and one in reverse parallel).
The conduction voltage of silicon diodes is generally greater than 0.5V, and below 0.5V, the forward resistance of silicon diodes is large, which has a small impact on the original internal resistance of the meter head and can be basically ignored.
When mismeasuring, an increase in voltage will cause a decrease in the forward resistance of the silicon diode, and most of the current will be diverted by the diode to protect the meter head.
