Preventive Measures for Multimeter Pointer Bending and Meter Head Burning
When using a multimeter, if the operation is improper, the pointer will be bent, and in serious cases, the meter head will be burned.
In order to prevent such accidents, pay attention to the following items when using the multimeter:
1) Before measuring, estimate the size of the object to be measured, and turn the range switch to the appropriate range.
If you don't know the size to be measured, you can turn the range to the maximum first, and then slowly approach the appropriate range.
Note that when measuring a large object with a small range, it is very likely to bend the pointer.
2) When measuring resistance, the circuit under test must be cut off from the power supply.
3) When testing high voltage or high current, it is forbidden to rotate the range switch. In order to prevent the contacts from arcing and damage the switch.
4) When measuring the electrolytic capacitor, it should be short-circuited and discharged before measuring.
5) When the multimeter is used incorrectly, the meter head may be burned.
Precautionary measures: connect two silicon diodes in parallel at the positive and negative ends of the meter head for protection (one forward parallel and one reverse parallel).
The conduction voltage of the silicon diode is generally greater than 0.5V, and the forward resistance of the silicon diode is very large below 0.5V, which has little effect on the original internal resistance of the meter and can basically be ignored.
When the error is measured, the voltage rise will reduce the forward resistance of the silicon diode, and most of the current will be shunted by the diode to protect the meter.
