How to test a relay

john February 16, 2010 11 Comments

This article shows you how to test a relay. A relay will usually have a coil, pole terminal and a set of contacts. The set of contacts that are open when the relay is not energized are called normally open (N/O) contacts and the set of contacts that are closed when the relay is not energized are called normally closed (N/C) contacts. The following steps can be used to perform the testing of the relay using a multimeter.

  • Keep the multimeter in the continuity check mode.
  • Check for continuity between the N/C contacts and pole.
  • Check for discontinuity between N/O contacts and the pole.
  • Now energise the relay using the rated voltage. For example use a 9V battery for energising a 9V relay. The relay will engage with clicking sound.
  • Now check for continuity between N/O contacts and pole.
  • Also check for discontinuity between N/C contacts and pole.
  • As a final test, measure the resistance of the relay coil using a multimeter and check whether it is matching to the value stated by the manufacturer.

If all the above tests are positive we can conclude that the relay is healthy.

TAKE A LOOK : WORKING OF RELAYS

TAKE A LOOK : TYPES OF RELAYS


Comments
  • ANISO DAVID
    September 17, 2014

    pleaese teach me how to test for electrical contactor and transformers

  • Komal
    February 9, 2014

    How to test 5 terminal relay?

  • Nazrul
    November 19, 2013

    I LIKE TO TEST A RELAY O(VAMP 210) WITH SVERKER 780. IT IS NEEDED STEP BY PORCEDURE. THANKS AND REGARDS. NAZRUL

  • darshan
    March 14, 2013

    pls tell me how to check the diod

    • Seetharaman
      March 16, 2013

      Hi use a multimeter in its diode continuity range. one way it should indicate 550 to 700mV and other way by inter changing the probe connecting to diode should show over range. If it is showing less in both ways then it is defective.

  • darshan
    March 14, 2013

    pls tell me how to check the diode

  • June 30, 2012

    Good list of tests for a relay.

    Great article.

  • September 5, 2011

    i have some oil circuit breaker and i want to convert it to in vacuum circuit breaker,plz send me all step to done it,

  • Gurjit Singh
    July 29, 2011

    Hello i am confuse in some point as i know that dc voltage is not given to coil because x=2pie*f*L and
    in dc f=0 so reactance is zero and current go to infinite

    then why we apply dc voltage to the relay and how dc can produce the magnetic field in the relay because

    in dc there is no variation and inductor pass it without any effect and

    no magnetic field produce when we apply dc to any inductor..?

    please give me the answer of that question so that i can come out of my confusion.

    • tilahun temechew
      October 20, 2014

      it is known that any current caring conductor can create magnetic field around the wire so, dc current can create magnetic field. As you say no time varying current in dc source but magnetic field can be created even with dc current. you have to know that alternating current is mandatory to create an EMF (ELECTROMOTIVE FORCE).

  • Feroj
    February 16, 2010

    Please send a how to test a relay.

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