How to Test TRIAC with Multimeter?
A thyristor is a four-layer semiconductor device, consisting of alternating P type and N type materials (PNPN). The four layers act as bistable switches. As long as the voltage across the device has not reversed (that is, they are forward biased), thyristors continue to conduct electric current. The most common type of thyristor is the silicon-controlled rectifier (TRIAC)
The triac is one of the important devices in the power semiconductor devices family. The triac is widely used for controlling the AC voltage.

How to test TRIAC with Digital Multimeter OR using Ohmmeter?
The symbol of the Triac:

1. The TRIAC is 5 layer, 3 terminal Power semiconductor device.
2. It has a pair of phase-controlled SCRs connected in an inverse parallel manner on the same chip.
3. It is a bidirectional device, which means it can conduct current in both directions.

Step by step Procedure:
1. The below steps explains how to test triac with a multimeter.
2. Select the multimeter setting on resistance mode.
3. find out the polarity of the ohmmeter lead using P-N junction diode. When positive lead is connected to the anode and negative lead is connected to cathode shows continuity.
4. The triac remains in its off state when the positive voltage is applied at MT1 and the negative voltage is applied at MT2 with gate current zero.
5. In a similar way, the triac remains in its off state when the positive voltage is applied at MT2 and the negative voltage is applied at MT1 with gate current zero.
6. In steps No. 3 &4 of triac testing, the ohmmeter should indicate no continuity through the triac. It means triac offers very high resistance. In this below step that Triac Good Condition.

In steps No. 3 & 4 of triac testing, if the ohmmeter shows continuity through the triac. It means triac is short circuit and defective. In this below steps shows that the triac is Faulty.

1. Now, if the gate of the triac gets positive voltage the device turns on either MT1 is positive with respect to MT2 or MT2 is positive with respect to MT1. This can be done by connecting the gate of triac to positive lead ( It may be MT1 or MT2 terminal, depending on which terminal has positive voltage through ohmmeter.

2. As per step No.8, the triac must turn on and must show very low resistance or continuity between MT1 and MT2. If triac shows continuity triac under test is OK.

If triac does not turn on as per step 8, triac offers very high resistance and triac is Faulty.

In this above steps following above steps, we can test the Triac with multimeter.

About the Author


Hello! My Dear Friends. I am Subramanian. I am writing posts on androiderode about Electronics testing and equipments.

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