October 1, 2011

Testing Capacitors with an Ohmmeter (Analog Multitester)

A capacitor may develop troubles like open, shorted and weak or leaky. Following are rules to be followed in testing capacitors:
  1. Switch off the power supply.
  2. To be safe and to protect your ohmmeter from damage, discharge the capacitor before testing. Do this by short-circuiting its two terminals with a conductor. Make sure that the conductor that you are using has an insulated handle to protect you from electric shock.
  3. Disconnect one terminal lead of the capacitor from the circuit before testing.
  4. Adjust your ohmmeter to appropriate range. Use the guide below in selecting the range to be used for a range of capacitance values.

    Capacitance                          Range
    0.01 uF to 1uF            X10K and above
    1uF to 47 uF               X1K
    47 uF to 1000 uF        X10
    1000 uF and above      X1
  5. Connect the test probes to the terminal of the capacitor.
    Test probes connected to the terminals of the capacitor
  6. Evaluate the meter deflection. Below are the guides in evaluating the meter deflection.

    Good Capacitor – the pointer needle will deflect to the right and will move back to its initial position.

    Defective Capacitor:
    Open – the pointer needle would not deflect at all. Shorted – the pointer needle will rest to zero ohm scale.
    Leaky - the pointer needle will deflect to the right and stays somewhere at the middle.

Meter deflection of a GOOD, OPEN, SHORTED and LEAKY Capacitor.
Click the picture to enlarge.


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