How to repair the multimeter resistance file pointer does not move
How to repair the multimeter resistance file pointer does not move
If the pointer multimeter can measure other measurements, but the pointer of the resistance gear does not move, you should check:
1. The resistance gear band switch is in poor contact.
2. The adjustable resistor (zero-adjustment fine-tuning, and some wire-wound fine-tuning) is short-circuited.
3. The shunt and step-down resistors are desoldered or burned.
1. Basic functions of multimeter
The modified multimeter is a novel-designed magnetoelectric system rectification portable multi-range multimeter. It can measure DC current, AC and DC voltage, DC resistance, etc., and has 26 basic ranges and levels, capacitance, inductance, and transistor DC parameters. etc. 7 additional reference ranges.
Second, the dial and gear plate
The dial and the gear plate are printed in red, green and black. The dial colors are respectively made according to AC red, transistor green, and the rest are black. It is easy to read when using. There are six scales on the dial, the first one is for testing For resistance; the second is for measuring AC and DC voltage and DC current; the third is for measuring transistor magnification; the fourth is for measuring capacitance; the fifth is for measuring inductance; the sixth is for measuring Audio level. Mirror mounted on the dial to eliminate parallax.
Except that there are separate sockets for AC/DC 2500V and DC 5A, the other gears only need to turn a selection switch, which is easy to use.
What is the reason for the high DC voltage measured by the multimeter and the low AC voltage?
There are two semi-variable potentiometers to adjust the measurement accuracy, one is welded behind the meter head, called R61, which is used to adjust the accuracy of the whole meter, and the other is welded to the upper left corner of the circuit board, called R33, which is specially used to adjust the AC voltage range precision.
Adjust R61 to the 50μA level, find a standard meter in series with this meter, connect a potentiometer with a dry battery for the power supply, adjust the potentiometer to make the standard meter close to full bias, and then adjust R61 to make the meter consistent with the standard value. If not consistent, check R10 of this form. After adjusting R61, the DC voltage file is ready.
Adjust R33 to switch to the AC 10V gear, and connect the appropriate AC low-voltage power supply in parallel with the standard meter, and adjust R33 to make the two indications consistent. If not consistent, you should check R32, R25 or diodes BG1, BG2 (diodes seldom go wrong).
