Naming of chip resistors 3

When testing with a multimeter, first select the appropriate resistance range of the multimeter based on the resistance value of the potentiometer being tested. Then, the following methods can be used for inspection. A. Use the ohms range of the multimeter to measure the resistance between terminals "1" and "2". The reading should be the nominal resistance value of the potentiometer. If the multimeter pointer does not move or the resistance value varies greatly, it indicates that the potentiometer is damaged. B. Check whether the contact between the moving arm and the resistor chip of the potentiometer is good. Use the ohms range of the multimeter to measure the resistance between terminals "1" and "2" (or "2" and "3"). Rotate the potentiometer shaft counterclockwise to a position close to "off". At this point, the smaller the resistance value, the better. Then slowly rotate the shaft clockwise, and the resistance value should gradually increase, and the pointer in the meter head should move smoothly. When the shaft is rotated to the extreme position "3", the resistance value should be close to the nominal value of the potentiometer. If the multimeter pointer jumps during the rotation of the potentiometer shaft, it indicates that there is a faulty contact in the moving contact. 5. Testing of Positive Temperature Coefficient Thermistor (PTC) During testing, use the multimeter in the R×1 range, and the specific operation can be divided into two steps: A. Room Temperature Testing (indoor temperature close to 25°C); touch the two leads of the PTC thermistor with the two probes to measure its actual resistance value, anddiode compare it with the nominal resistance value. If the difference between the two values is within ±2Ω, it is normal. If the actual resistance value differs greatly from the nominal resistance value, it indicates that its performance is poor or it has been damaged. B. Heating Testing; Based on the normal room temperature test, the second step of testing - heating testing can be carried out. Place a heat source (such as an electric soldering iron) near the PTC thermistor to heat it, and simultaneously use the multimeter to monitor whether its resistance value increases with the increase in temperature. If it does, it indicates that the thermistor is normal. If the resistance value does not change, it indicates that its performance has deteriorated and it cannot be used anymore. Be careful not to place the heat source too close to or directly contact the PTC thermistor to prevent it from being burned.diode