How to test an SCR

john May 21, 2009 17 Comments

Testing SCR using a multimeter.
A multimeter can be used to test SCRs quite effectively. The first procedure is to check the diode action between the gate and cathode terminals of the SCR. This test is just like what you have done in the case of testing a silicon diode (see testing a silicon diode).

Now put the multimeter selector switch in a high resistance position. Connect the positive lead of multimeter to the anode of SCR and negative lead to the cathode. The multimeter will show an open circuit. Now reverse the connections and the multimeter will again show an open circuit.

Then connect the anode and gate terminals of the SCR to the positive lead of multimeter and cathode to the negative lead. The multimeter will show a low resistance indicating the switch ON of SCR. Now carefully remove the gate terminal from the anode and again the multimeter will show a low resistance reading indicating the latching condition. Here the multimeter battery supplies the holding current for the triac. If all of the above tests are positive we can assume the SCR to be working fine.

Circuit for testing SCR.

This is another method for testing an SCR. Almost all types of SCR can be checked using this circuit. The circuit is just a simple arrangement for demonstrating the basic switching action of an SCR. Connect the SCR to the circuit as shown in diagram and switch S2 ON. The lamp must not glow. Now press the push button switch S1 ON and you can see the lamp glowing indicating the switch ON of SCR. The lamp will remain ON even if the push button S1 is released (indicates the latching).If the above checks are positive then we can conclude that the SCR is fine.

circuit-for-testing-scr

Comments
  • February 26, 2015

    plz sir can u give me a single circuit to test scr and transistor

  • April 3, 2014

    this is a very good method to test the scr

  • jet
    October 16, 2013

    An scr is not a triac.

    • Mark
      June 25, 2015

      Agreed, that is not a Triac. It is an SCR or Thyristor

  • July 25, 2013

    Its a great projetc… i think it will help me a lot. i had subscribed today.. i am a Student of E&C in Delhi.. Please update me daily with this type of articles.

    thanks

  • Fixer
    May 30, 2013

    1. test K-G for diode response.

    2. connect A to +, K to -. Test for high res.

    3. connect A to +, K to -. Test for high res.

    Steps 2 & 3 are the same. Your test procedure is wrong.

  • waleed21
    April 24, 2013

    plz accept me in your webside and send me all new information to my email .
    Thanks

  • P.PURUSHOTHAMAN
    July 14, 2012

    GOOD. EASY AND CORRECT TESTING METHOD.NEED NOT GO FOR THEORITICAL CALCULATION AND ARGUMENTS

  • Pathan Hasan
    March 15, 2012

    Thank u very much fro help,inspitie of an engineer i m not aware of how to test it, but i can easily test SCR

  • Hemchand
    August 5, 2011

    Thanks for helping hobbist&beginners.

  • May 11, 2011

    […] Test scrTaken from: http://www.circuitstoday.com/how-to-test-an-scr […]

  • April 23, 2011

    I think that 270 ohms is too small and would blow up the gate at 12 V on some SCRs. Plus an SCR is not a triac.

    I have a CR6CM-12 which only draws 0.015 amps at the gate.

    0.015 x 270 = 4v

    12v – 4v = 8v

    The gate on mine is maximum 6v. 8v is too much.

  • January 26, 2011

    […] 03:17 PM Hi all, I'm new here. I built a simple SCR circuit similar to the one on this page: http://www.circuitstoday.com/how-to-test-an-scr The differences are 1. I used an LED instead of a lamp. 2. The resistance at the gate is 1k ohm. 3. […]

  • nishant
    October 26, 2010

    if a scr is given but i dont no which terminal is anode cathode or gate how can i know the terminals using multimeter

  • srikanth
    March 5, 2010

    hello ahmed first of all u must know the basics

  • ahmed
    November 11, 2009

    hi
    plz what is the meaning of S2,also in test of SCR where can i wired the (-12) the second pole of Dc.

    • admin
      November 13, 2009

      Switch S2 can be used bring back the SCR from the latching state.

      negative end of the DC must be connected to the ground of the circuit

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