As we all know, the potentiometers are widely used in our life. In the process of using potentiometers, sometimes we need to check whether they are good or bad. How should we check them for those who are not professionals?

1. Appearance inspection

For the fixed resistance, first check the mark is clear, the protective paint is intact, no burning, no scars, no cracks, no corrosion, and the resistance body is in close contact with the pin. The adjustable power resistor should also check that the rotating shaft is flexible, tight and comfortable. The potentiometer with switch should check whether the action of switch is normal.

2. Multimeter Detection

(1) Detection of Fixed Resistance
The resistance of the multimeter is measured by the resistance of the multimeter, and different times of the multimeter are selected for measuring the resistance of different resistance values. For the pointer multimeter, because the indicator number of resistance is non-linear, the larger the resistance value, the more dense the indicator number, so choosing the appropriate range, the needle deflection angle should be larger, indicating the full range of 1/3-2/3, and reading more accurately. If the measured resistance exceeds the error range of the resistance, the resistance value is infinite, the resistance value is 0 or the resistance value is unstable, it indicates that the resistor has been damaged.
In the measurement, attention should be paid to the hand holding resistance not to contact with the two pins of the adjustable variable resistor, which will make the resistance presented by the hand parallel to the measured resistance and affect the accuracy of the measurement. In addition, the resistance of the resistor in the circuit can not be detected by the multimeter resistor when it is not live. On-line detection should first power off, then interrupt the resistance from the circuit, and then measure.

(2) Detection of Fuse Resistance and Sensitive Resistance of Volume Adjustable Potentiometer
The resistance of fuse is usually only a few to several dozen Euros. If the measured resistance is infinite, it has been fused. It can also measure the resistance of the fuse on-line, and measure the voltage between the two ends to the ground. If one end is the power supply voltage and the other end is 0 volt, the resistance of the fuse has fused.
There are many kinds of adjustable variable resistor. Taking thermistor as an example, they are divided into positive temperature coefficient and negative temperature coefficient thermistors. For positive temperature system (PTC) thermistors, the general resistance value is not large at room temperature. When the thermistor is near the resistance by hot soldering iron in the measurement, the resistance value should increase significantly, indicating that the resistance is normal. If there is no change, the negative temperature system thermistor will be the opposite.
When the adjustable power resistor is not illuminated (with hands or objects covering the light), the resistance value measured by the multimeter is large, and the resistance value indicated by the photometer needle decreases obviously. If there is no change, the component will be damaged.

(3) Detection of Variable Resistance and Potentiometer
Firstly, the resistance between the two fixed terminals is measured to be normal, if it is infinite or zero Euro, or if the difference between the resistance and the nominal value is large enough to exceed the allowable error range, all of them are damaged; if the resistance of the resistor body is normal, then one of the multimeter's pen-to-potentiometer sliding end and the other one's pen-to-potentiometer (adjustable power resistor) fixed end are rotated slowly to observe whether the pin changes smoothly. When turning from one end to the other, the resistance changes from zero Euclidean to nominal value (or vice versa), and there is no jump or jitter, which indicates that the potentiometer is normal. If there is jump or jitter in the process of turning, it means that the sliding point shows poor contact of the adjustable variable resistor.