Mastering Capacitor Testing: An In-depth Guide to Measuring Capacitance with Precision

What is a capacitor and how does it work?

A capacitor is a passive electronic component that stores electrical energy in the form of an electrostatic field. It is made up of two conductive plates separated by an insulating material called a dielectric. When a voltage is applied across the capacitor, opposite charges build up on the two plates, creating an electrostatic field between them.

Capacitors are widely used in electrical equipment such as single-phase compressors and fans for several reasons:

• They are used to smooth the supply voltage by quickly absorbing or releasing energy when the voltage varies.
• They allow the starting of single-phase motors by providing an out-of-phase phase necessary for the initial torque.
• They filter high frequency noise present on the electrical network.

Visually checking the health of a capacitor

Before proceeding with further testing, it is important to visually examine the capacitor to identify any apparent signs of malfunction. Here are some clues that may indicate a problem:

• Swelling or leaking capacitor housing
• Traces of burning or oxidation on the terminals
• Loose or broken cables

If any of these signs are present, it is best to replace the capacitor rather than attempt a repair.

Discharge a capacitor safely

Before testing a capacitor, it is essential to discharge it to avoid any risk of electrocution. Here’s how to do it:

1. Turn off the power supply and unplug the device containing the capacitor.
2. Get a resistor (for example 10 kΩ) and a pair of insulated pliers.
3. Grasp the resistor with the insulated tweezers and place one end on each terminal of the capacitor for a few seconds. This operation will allow the energy stored in the capacitor to dissipate through the resistor.

Testing a capacitor: two main methods

1. Load test with a multimeter in ohmmeter mode:

For this method, you will need a multimeter that can measure electrical resistance (in ohms). Follow these steps:

1. Set your multimeter to ohmmeter mode (Ω symbol).
2. Place the test probes of the multimeter on the terminals of the discharged capacitor. Polarity does not matter for this method.
3. Observe the value displayed by the multimeter. If the capacitor is in good condition, the resistance should increase quickly to infinity (or a very high value). If it remains low or zero, this indicates a short circuit in the capacitor. If it doesn’t change at all, it means the capacitor is open (faulty).

2. Capacity test:

This method allows the capacitance of the capacitor to be directly measured in microfarads (µF) and requires a specific instrument called a capacitance meter or a current source and a current clamp.

Direct measurement with a capacitance meter:

1. Set your capacitance meter to capacitance mode (symbol F).

   …..,

   > &nbspan>; Does he have this setting?

2. Place the test probes of the capacitance meter on the terminals of the discharged capacitor. Respect the polarity if your device tells you to do so.