Preventive Measures for the Bent Pointer of a Multimeter and the Burnout of Its Meter Head
To prevent such accidents, pay attention to the following points when using a multimeter:
Before measurement, estimate the magnitude of the quantity to be measured and set the range switch to an appropriate range.
If you're unsure about the magnitude of the quantity, set the range to the maximum first and then gradually adjust it to a more appropriate range.
Note that when measuring a large quantity with a small - range setting, it's highly likely to bend the pointer.
When measuring resistance, you must disconnect the circuit to be measured from the power supply.
When testing high - voltage or large - current circuits, do not rotate the range switch. This is to prevent arcing at the contacts, which may damage the switch.
When measuring electrolytic capacitors, short - circuit them to discharge first and then conduct the measurement.
The meter head may burn out if the multimeter is misused.
Preventive measure: Connect two silicon diodes in parallel across the positive and negative terminals of the meter head (one in forward - parallel and the other in reverse - parallel).
The forward - conduction voltage of silicon diodes is generally greater than 0.5V. Below 0.5V, the forward resistance of silicon diodes is very large, which has little impact on the original internal resistance of the meter head and can be basically ignored.
In case of incorrect measurement, when the voltage rises, the forward resistance of the silicon diodes will decrease. Most of the current will be shunted through the diodes, thus protecting the meter head.
