Instructions for using a pointer multimeter to detect the quality of rectifier diodes
A diode has unidirectional conductivity. Apply forward voltage to conduct and reverse voltage to cut off. Its forward resistance is small, and its reverse resistance is large, which is the basis for detection.
1, Normally, for a single rectifier diode, the multimeter should be set to the ohm range of Rx100 or Rx1K before testing. Connect the two probes to the two leads of the diode and measure the resistance value. Then switch the pens of the two meters and measure the resistance value again. Finally, compare the results of the two measurements.
If the resistance value is high and low, it indicates that the rectifier diode is normal. When the resistance is low, the black probe is connected to the positive terminal of the diode, and the red probe is connected to the negative terminal of the diode.
If both resistance values are high, it indicates that the diode is open circuit.
If the resistance value is small twice, it indicates that the diode is short circuited.
It should be noted that the measured resistance values may vary depending on the gear selected.
2, During actual maintenance, it is often necessary to solder the diode out of the circuit, which can be quite troublesome. In fact, it is also possible to directly perform online detection without soldering the rectifier diode. The method is simple and the effect is good. I am sharing it now for reference.
Power on the electrical equipment normally (AC), set the multimeter to the AC voltage range, select the specific range based on the rectified voltage, connect the red probe to the positive terminal of the rectifier diode and the black probe to the negative terminal, and measure an AC voltage value. Swap the probes again and measure another voltage value. Using the same method, set the range of the multimeter to the DC voltage range and measure a DC voltage value. Then compare the results.
If the first measured AC voltage value is about twice the DC voltage value, and the second measured AC voltage is zero, it indicates that the rectifier diode is normal.
If the difference between the two measured AC voltage values is not significant, it indicates that the diode has broken down.
If the voltage values measured twice are both zero, it indicates that the diode has short circuited.
If the second measured value is neither zero nor equal to the first value, it indicates that the performance of the diode has deteriorated.
