Preventive measures for bending pointer and burning meter head of multimeter
When using a multimeter, the pointer will be bent if it is improperly operated, and the meter will be burned when the situation is serious.
In order to prevent such accidents, pay attention to the following items when using multimeter:
1) Before measurement, estimate the measured size and turn the range switch to the appropriate range gear.
If you don't know the measured size, you can first dial the range to the maximum gear, and then slowly approach the appropriate range gear.
Note that when measuring a large measured object with a small range gear, it is very likely to bend the pointer.
2) When measuring the 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 avoid contact arc and damage the switch.
4) When measuring electrolytic capacitance, short-circuit discharge shall be performed before measurement.
5) When the multimeter is used incorrectly, the meter head may be burned.
Precautions: Connect two silicon diodes in parallel at the positive and negative ends of the meter to protect it (one is in forward parallel and the other is in reverse parallel).
The turn-on voltage of silicon diode is generally greater than 0.5V, and the forward resistance of silicon diode is very large below 0.5V, which has little influence on the original internal resistance of meter head and can be basically ignored.
When the measurement is wrong, the forward resistance of the silicon diode will be reduced by the voltage increase, and most of the current will be shunted by the diode to protect the meter.
