How to test SCR with Multimeter?
Testing SCR with Multimeter :
How to test the Silicon Controlled Rectifier [SCR] using Multimeter?
This post will discuss about testing SCR - Silicon Controlled Rectifier with the help of Multimeter or Ohmmeter.
It is highly recommended to read about thyristor (SCR) basics before proceeding further.
Click here to know more about SCR - Introduction, Structure, Characteristics
The thyristor pin assignment diagram of TO-220 package is given for ready reference. If you are using Ohmmeter Read the following paragraph else skip it and proceed to next paragraph.
Identify the terminals of the Ohmmeter:
- Using a junction diode, we can find out which ohmmeter lead is positive and which is negative.
- Connect the general purpose PN junction diode to across the positive and negative terminals of the Ohmmeter.
- The ohmmeter will indicate continuity only when the positive lead is connected to the anode of the diode and the negative lead is connected to the cathode.
- The SCR can be tested with an ohmmeter based on this concept.
Procedure to Test the SCR with the help of Multimeter:
- To test the SCR, keep the Multimeter into Ohmmeter mode.
- Connect the positive output lead of the multimeter to the anode and the negative lead to the cathode.
- The multimeter should indicate no continuity.
- Touch the gate of the SCR to the anode.
- The multimeter should indicate continuity through the SCR.
- When the gate lead is removed from the anode, conduction may stop or continue depending on whether the multimeter is supplying enough current to keep the device above its holding current level.
- If the multimeter indicates continuity through the SCR before the gate is touched to the anode, it indicates that the SCR is shorted.
- If the multimeter will not indicate continuity through the SCR after the gate has been touched to the anode, it indicates that the SCR is open.
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