What do you measure capacitance in

Recall that farads is the unit of measurement for a capacitor. The image below shows a run capacitor used in HVAC systems. Setting your device up. To measure capacitance, you will need to plug your leads into the correct ports on your multimeter. This is the symbol for capacitance. Before taking any measurements, you need to set your multimeter dial to measure capacitance. See the image above for an example. Recall each dial position on a multimeter can have multiple measurements.

To measure the farads of a capacitor, the capacitor must be disconnected from the circuit. You must be careful when handling capacitors. You risk being shocked when touching a capacitor since it stores electrical charge. Even when the power is off, the capacitor will have stored energy. If you touch a capacitor before it has been discharged, you will be shocked or injured.

Once the power is turned off , you must discharge the capacitor. In the field, it is common for technicians to touch the metal part with an insulated screwdriver across the two terminals to discharge it. When a meter measures capacitance, it sends a small test current through the capacitor.

The multimeter reads this test current to determine the farads of the capacitor. In order to accurately measure this test current, the capacitor needs to be discharged. Part One. Turn off the power to the circuit. Part Two. Discharge the capacitor by touching the metal end of an insulated screwdriver across both terminals. Be sure that you are not touching the metal end of the screwdriver.

Remove the capacitor from the circuit. Log in Social login does not work in incognito and private browsers. Please log in with your username or email to continue. No account yet? Create an account. Edit this Article. We use cookies to make wikiHow great. By using our site, you agree to our cookie policy. Cookie Settings.

Learn why people trust wikiHow. Download Article Explore this Article methods. Tips and Warnings. Related Articles. Article Summary. Method 1. Choose a tool that will measure capacitance. Even cheap digital multimeters often have a capacitance setting "— —. They do give accurate results for most film capacitors, since these behave more like the ideal capacitors your multimeter's calculations assume. These tools can cost several thousand US dollars, but have several reliable ways to test capacitance.

This guide focuses on multimeters. LCR meters should come with a detailed instruction manual specific to your device. ESR meters equivalent series resistance meters can conduct tests on capacitors while they are in a circuit, but do not measure capacitance directly. Shut off the power to the circuit. Confirm that the power is off by setting your meter to test for voltage.

Place the leads on opposite sides of the circuit's power source. If the power was successfully shut off, the voltage should read zero. Discharge the capacitor carefully. A capacitor can hold charge for several minutes after the power is disconnected, or even longer in rare cases. Connect a resistor across the capacitor terminals so the charge can drain safely. Large capacitors found in appliance power supplies, camera flash circuits, and large motors can hold a dangerous or lethal amount of charge.

Experienced supervision is recommended. Disconnect the capacitor. Testing while the capacitor is part of a circuit can give very inaccurate results, and potentially damage other components. Remove the capacitor carefully, desoldering the connection if necessary. Method 2. Set the multimeter to measure capacitance. Providing a logic level of 3. How on earth is this achieved? There are many ways to measure capacitance, If you have a waveform generator you can either use a square wave and measure the rise time.

Or a sine wave and measure the current and voltage. If you know current and voltage, you know what your load is. If the load is a capacitor, you'd also need phase information. The links below go into more depth on how this is done.

Instead of an waveform generator, the DMMs usually have a simpler circuit usually only generating one or a few frequencies. Instead of an oscilloscope circuits that measure phase and amplitude to do the calculations. The cool thing is, if you have an oscilloscope and waveform generator, you can also measure capacitance, sometimes better than a DMM.

This also works for inductance to. Even though RLC meters use a more precise constant current sinewave at selected frequencies to measure voltage amplitude and phase shift to compute all values, they still do not go up to 1 Farad.

So the Fluke only measures up to uF. The Keysight portable meters measure only up to Edit: The high impedance is only for the voltage measurement setting. The impedance is much much lower when measuring capacitance. According to Fluke :. A multimeter determines capacitance by charging a capacitor with a known current, measuring the resulting voltage, then calculating the capacitance. They are not waiting for the RC time constant. They may also do the same thing discharging the cap, in a loop.