Multimeter pointer bending and head burning preventive measures
1) Before measurement, estimate the size of the measurement and set the range switch to the appropriate range.
If you are not sure of the size of the measurement, you can first set 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 disconnected 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 them and discharge them before measuring.
5) When using the multimeter incorrectly, the meter head may be burned.
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.
Precautions
1> Measurement of current and voltage can not choose the wrong gear. If you mistakenly choose the wrong resistance or current gear to measure the voltage, it is very easy to burn out the meter. When the multimeter is not in use, it is best to rotate the gear to the highest level of AC voltage to avoid damage due to improper use.
2>When measuring current and voltage and DC current, pay attention to "+" "-" polarity, can not be connected to the wrong. If you find that the pointer begins to reverse, both should immediately switch the meter stick to avoid damage to the pointer and the meter head.
3>If you don't know the size of the measured voltage or current, you should use the highest grade first, and then choose the appropriate grade to test, so as to avoid excessive deflection of the needle and damage to the meter head. The closer the selected gear is to the measured value, the more accurate the measured value will be.
4>When measuring the resistance, do not touch the bare ends of the components (or the metal parts of the two bars) with your hands, so as to avoid the parallel connection of the human body resistance and the measured resistance, which will make the measurement result inaccurate.
5> Measurement of resistance, such as the two sticks shorted, adjust the "zero ohm" knob to the maximum, the pointer is still not up to 0, this phenomenon is usually caused by insufficient voltage of the battery inside the table should be replaced with new batteries can be measured accurately.
6>When the multimeter is not in use, don't choose the resistance gear, because there are batteries inside, such as accidentally easy to make the two rods touch the short circuit, not only consume batteries, and in serious cases, it will even damage the meter head.
