Preventing multimeter pointer bending and head burning
To prevent such accidents, pay attention to the following matters when using the multimeter:
(1) Before measurement, estimate the size of the measured and set the range switch to the appropriate range gear.
If you are not sure of the size of the measurement, 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 resistance, the circuit under test must be cut off from the power supply.
3) It is forbidden to rotate the range switch when testing high voltage or high current. In order to avoid contact arc, damage to the switch.
4) When measuring electrolytic capacitors, short-circuit and discharge them before measuring.
5) When using the multimeter incorrectly, the meter head may be burnt.
Preventive measures: Connect two silicon diodes in parallel with the positive and negative ends of the meter head to protect it (one forward parallel, one reverse parallel).
Silicon diode on voltage is generally greater than 0.5V, below 0.5V silicon diode forward resistance is very large, the original internal resistance of the meter head has a small impact, basically negligible.
When mismeasurement, the voltage rise will make the silicon diode forward resistance decrease, most of the current is shunted by the diode, play the role of protecting the meter head.
