Multimeter can easily detect the problem of poor contact of potentiometer and operating procedures
Check if the movable arm of the potentiometer is in good contact with the resistor. While measuring the resistance value with a multimeter, rotate the potentiometer shaft and observe the oscillation of the pointer. When measuring, set the multimeter to the resistance mode, connect one probe to the "2" end of the potentiometer's movable arm, and connect the other probe to the "1" or "3" end of the resistor body. Measure the resistance value at the "1", "2" or "2", "3" ends. Generally, R12+R23=R13. At the same time, rotate the potentiometer shaft counterclockwise, then clockwise, and observe the pointer of the multimeter. A normal potentiometer and multimeter pointer should move back and forth smoothly. If the pointer moves unstably or jumps, it indicates a fault of poor contact between the potentiometer arm and the resistor, as shown in the figure.
For potentiometers with switches, it is also necessary to check whether the switch of the potentiometer is in good condition. Use the resistance mode of the multimeter, connect the two probes to the switch contacts "4" and "5" respectively, rotate the potentiometer shaft or push and pull the potentiometer shaft alternately to "turn on" and "turn off" the switch, and observe the multimeter pointer indication. When the switch is turned on, the pointer of the meter should point to the far right (with zero resistance); When the switch is turned off, the pointer of the meter should point to the far left (with an infinite resistance). It can be repeatedly tested several times to observe whether the switch has poor contact faults.
Key points to note:
Select the appropriate gear, connect the probes to terminal 1.3, measure the nominal values at both ends, check the contact of the body arm, measure the resistance while observing the needle movement, and then test whether the switch is good. It is good to turn on zero and turn off if not.
