When a 10 µF capacitor is connected across the terminals of an ohmmeter, the instrument initially shows low resistance and then slowly the value of resistance rises to a very high value.

When a 10 µF capacitor is connected across the terminals of an ohmmeter, the instrument initially shows low resistance and then slowly the value of resistance rises to a very high value. What conclusion can be drawn about the condition of the capacitor?

Right Answer is:

The capacitor is straight

SOLUTION

Testing of Capacitor

To really test a capacitor, two conditions must be assessed.

  • One is the condition of the dielectric, and the other is the condition of the plate area.
  • The first test can be made with an ohmmeter.
  • If an ohmmeter is connected across the terminals of a capacitor, the meter should show a deflection upscale and then return to infinity ohms.
  • The deflection upscale indicates current flow to the capacitor when it is being charged by the ohmmeter battery.
  • If the leads of the ohmmeter are reversed, the meter should deflect twice as far upscale and then return to infinity occurs.
  • If a digital ohmmeter is employed, it should indicate either infinity or very high resistance in the megohm range. That indicates that the capacitor is straight and is working fine.

  • The ohmmeter test for a capacitor is actually a very poor test.
  • This test will not indicate a broken plate that would lower the value of capacitance.
  • The ohmmeter test can indicate a show circuit, but it cannot test the condition of the dielectric.
  • To test the dielectric rated voltage must be applied to the capacitor.
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