Testing An Electric Capacitor With The Help Of Ohm-meter

The remaining capacity of the capacitor can be concluded with the use of an ohm meter. Normally, ohm meter tells you about the power and the remaining charging capacity of the capacitor. As capacitor can accumulate charge even when it is not attached to an electrical source, be sure to discharge it before testing.

Since capacitor is the power house unit of electrical appliances, they can give you bad time if you touch the terminals of a charged capacitor. To avoid such mishaps, always discharge the capacitor before testing it. You can discharge it through a screw driver which has an insulated handle. Touch both the probes of the capacitor on the metal end of the screw driver and it discharges along with a spark.

Now, switch on the ohm meter and change the setting to 'ohm'. Some ohm meters don't have 'ohm' indicator. In such a case, switch the indicator to RX1. RX1 indicates that all the readings are measured with a one-to-one ratio.

Touch both the probes to each other and zero the meter by adjusting the knobs placed on the meter. Zero value is located on the extreme right of the meter and the extreme left is known as infinity.

Now, touch the red lead to the one terminal of the capacitor and the black lead to another. The pointer of the meter will move towards the zero and then slowly to the left (infinity). This indicates that the capacitor is in a healthy condition. The constant fluctuation of the meter denotes the healthy status of the charging and discharging process.

Next, reverse the position of the leads on the capacitor terminals. If no difference occurs then it is ok. If however the needle deflects towards the right (zero ohm) and does not come back to left (infinity) then it refers to a shorted capacitor.

In case the needle of the meter never deflects then a wide open circuit or an internal break is detected in the capacitor. In both the cases, the capacitor needs to be replaced.

Make sure that the capacitors replaced once they have exceeded their expiry period.