Preventive Measures for Bend of Multimeter Pointer and Burning of Meter Head
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.
The process of installing the brush knob and gear position of the multimeter
1. Take out the spring and steel ball, put them in Vaseline oil, put the spring with lubricating oil into the small hole of the brush knob, and the steel ball will stick to the top of the spring. Don't lose it.
2. The brush knob installation part on the back of the observation panel is composed of 3 brush knob fixing clips, 2 brush rotation steel positioning arcs, 1 steel ball installation groove and 1 petal-shaped steel ball rolling groove.
3. Put the brush knob flat on the panel, and pay attention to the direction in which the brush is placed. Use a screwdriver to gently push the steel ball into the petal groove, carefully roll it off, and evenly force the brush knob into the fixed card with your fingers.
4. Turn the panel to the front, gently set the gear switch knob on the small handle protruding from the round hole, turn the knob slowly to check whether the brush knob is installed correctly, you can hear "click", "click" Click" positioning sound.
If you can't hear it, it means that the steel ball is missing or has fallen into the gap between the brush knob and the panel, and the gear switch cannot be positioned and needs to be removed and reinstalled.
5. Gently remove the gear switch knob, gently press the handle in the small hole with your hand, and at the same time gently pull the 3 positioning cards one by one on the opposite side, the force must be light and even, so as not to break the positioning card, be careful The steel ball cannot roll off.
