January 24, 2022



Test Zener Diodes with Three Simple Methods

As one of important part of Zener Diode Tutorial, test a Zener diode is commom during use.

1. Resistance Measurement

The resistance measurement method is generally more practical to measure the tube voltage regulation value below 10V, because the maximum voltage of the stacked battery is 9V from the analog multimeter we use.

The principle of the test is: through the multimeter RX10K block, the internal power supply is 9V at this time to make the internal PN junction of the diode to be in a reverse breakdown state, which will have a relatively small resistance.

Another way is using a multimeter to measure the forward and reverse resistance in the R×1k block. Normally, the reverse resistance is relatively large. If the needle swings or other abnormal phenomena are found, it indicates that the regulator tube has poor performance or even damage. The method of energizing in the road can also roughly measure the quality of the Zener tube. The method is to measure the DC voltage at both ends of the Zener tube with the DC voltage file of a multimeter. If the voltage close to regulation value, the diode is basically intact; if the voltage deviates too much from the nominal voltage regulation value or is unstable, the voltage regulator tube is damaged.

The disadvantage is that it can only measure the quality of Zener diodes below 10V, and can only be measured with an analog multimeter.

The diode block of the multimeter can also be used to measure the quality of the Zener tube. When measuring, adjust the multimeter’s range switch to the diode position firstly, and then touch the positive and negative poles of the regulator tube with the red and black test pens. If the tube is normal, the multimeter will display a reading of about 0.700. Next, Change the two test pens. And measure the reverse resistance of the Zener tube. If it is a good tube, the reading will be “1”; if the positive and negative readings of the Zener tube are both “0.000” or both are “1” during the measurement, it means that the Zener tube is damaged.

2. Voltage Measurement

This measurement method is relatively simple. We generally use the DC voltage file of the digital multimeter to directly measure the output voltage regulation value of the Zener diode. If the measured DC voltage result is equal to the voltage regulation value of the Zener diode, it means that this is stable. The pressure diode is working normally, which also shows that the diode is good.

3. Measuring Zener Diode with Megger

For Zener diodes with higher regulated voltages, sometimes we can also use a megger to detect them. We connect the terminal of the megger to the diode and shake the handle of it according to the rated speed. When it is found that the megger is relatively stable at a certain value, it means that the quality of the Zener diode is good. If the swing is more severe, it means that the Zener diode is poor or is not a Zener diode.

We all know that the Zener diode works in a breakdown state, so you can use this feature to distinguish whether it is an ordinary diode or a Zener tube. Use a 500-volt megger, and its output terminal is connected in parallel with a multimeter, either digital or analog meter. Adjust the voltage of the multimeter to 500 volts, shake the megger to make the needles deflect in the positive direction, at this time, the red test lead is positive.

Then connect the two test leads to the two electrodes of the tested tube. If you know the electrodes of the tested tube in advance, connect the red test lead to the negative electrode of the tested tube, shake the megger, and the voltage value measured on the meter is regulator voltage value, that is the voltage stabilization value of the Zener tube. If you don’t know the electrodes of the tube under test, first shake the megger to see the voltage. If there is no voltage (0.5 volt), change the test lead and test again. This method is suitable for detecting Zener diodes below 200 volts. If the measured voltage exceeds 200 volts, it may not be a Zener diode.

submitted by /u/Ross713kk
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