In this multimeter use guide, learn how to measure capacitance of a capacitor within a circuit using a multimeter. Understand what capacitance measurement and capacitors are, the importance of maintaining capacitors, units of capacitance, and how to use a multimeter to measure a capacitor's capacitance.
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Multimeter Basics
There are two types of multimeters: digital multimeters and clamp multimeters. Most of what is pictured in this guide is a digital multimeter.
Multimeters can be used to measure various electrical measurements:
Measure voltage in Volts
Measure current in Amperes
Measure resistance in Ohms
Measure continuity in Ohms
Measure capacitance in Farads - this is the focus of this guide!
Measure temperature in Farenheit or Celcius
Multimeters have 2-4 ports for the provided test leads to be plugged into.
Test leads have one end of the wire called the plug end that plugs into the multimeter port. The other end of the wire called the probe end is used to touch the component of measurement.
Remember that black lead represents the negative probe, and red lead represents the positive probe.
Ensure that the probe ends of your test leads do not touch as you measure using the multimeter, as that can short the circuit and become a safety hazard.
Instead of test leads, alligator clips can also be used.
Why Should You Measure Capacitance?
Capacitance is the ability of an electronic component - often a capacitor - to store an electrical charge. Capacitance measurement refers to the "capacity" of charge a capacitor holds. The unit of measurement for a capacitor is farads, with more accurate readings using microfarads.
Capacitors are electronic components that store electrical energy or charge without producing it. There are many types of capacitors for different circuits and purposes - for example, electrolytic capacitors are used in filtering devices whereas film capacitors are used for energy discharge applications.
Malfunctioning or faulty capacitors is a common cause to failed circuits due to having limited life. Checking capacitance measurements consistently helps to tell if your capacitor is still working effectively or if it short circuited. If your capacitor short circuits, it means that the fuse has been blown and cannot be used; surrounding electronic components may also be effected.
Digital multimeters are the most common tool used to measure capacitance and many other electrical measurements. A capacitance meter is also used to measure capacitance. A capacitance meter may used in more special cases, as digital multimeters can only measure capacitance under a constant DC voltage signal.
Setting Up Your Multimeter To Measure Capacitance
To measure the farads or microfarads of a capacitor, the capacitor must first be disconnected from the circuit. It's important to stay careful when handling capacitors connected to a circuit. 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.
When a digital multimeter measures capacitance, it sends a small test current through the capacitor. The multimeter reads this test current to determine the farads or microfarads of the capacitor. In order to accurately measure this test current, the capacitor needs to be discharged.
Let’s learn how to discharge the capacitor before removing it from the circuit:
Turn off power to the circuit. You can test if a circuit is off by measuring its voltage.
Once the power is turned off, begin discharging the capacitor.
Discharge the capacitor by touching the terminals with a 20,000 Ω, 5-watt resistor across the capacitor terminals for five seconds.
Technicians typically touch the metal part of a capacitor with an insulated screwdriver across the two terminals to discharge it for safety.
To set up your meter for capacitance measurement, you first need to plug your test leads into the correct ports on your digital multimeter:
Your red lead goes into the port marked with the "–|(–” symbol. This is the capacitor symbol.
Your black lead is plugged into the port marked with “COM”.
Afterwards, you need to set your multimeter dial to the capacitor symbol for capacitance measurement:
Rotate the dial until it points at the "–|(–” capacitor symbol. This capacitor symbol is universal on all multimeters for capacitance measurement.
On some multimeters, you might need to use the yellow function key to set the multimeter to the capacitance symbol instead. This is because each dial position on a multimeter can have multiple measurements. Press the yellow function key until the "–|(–” capacitor symbol appears on your display.
Taking Capacitance Measurement With A Multimeter
Making Sure You're Set Up
Turn off the power to the circuit.
Discharge the capacitor.
Remove the capacitor from the circuit.
Confirm that test leads are in the right location: your black lead should be plugged into the “COM” port and your red lead should be plugged into the port marked with the capacitor symbol "–|(–”.
Set your dial so that the arrow points to the "–|(–” capacitor symbol. Otherwise, make sure to use the function key to set your meter to the capacitor symbol instead.
Measuring Capacitance
Remember to remove the capacitor from the circuit. To stay safe, wear insulated gloves and safety glasses when handling any type of electrical equipment.
Place one test lead on each terminal of the capacitor. Be sure that your hands do not touch the capacitor. This can interfere with the measurement. As you touch the test leads to the capacitor, a value will appear on the display. When a steady value is being displayed on the multimeter screen, that is your capacitance measurement. Note the units displayed on the meter. For example, the meter might display microfarads.
Some multimeters require you to manually set the range of your measurement. If your multimeter is not auto ranging, you may need to adjust your range until you get an accurate result. Do this by slowly turning the dial to a lower range setting. Stop once you have an accurate read out.
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FAQs
What is capacitance?
Capacitance refers to the ability of a system (like a capacitor) to store electrical charge. The unit of capacitance is the farad (F), although microfarads (µF) are often used for more precise measurements in smaller components.
How do I measure capacitance with a multimeter?
To measure capacitance, first, ensure the capacitor is disconnected from the circuit. Then, discharge the capacitor, plug the multimeter leads into the correct ports (red lead into the port marked with the capacitor symbol “–|(–”), and set your multimeter to the capacitance measurement mode. Place the leads on each terminal of the capacitor and read the measurement on the multimeter.
Do I need to remove the capacitor from the circuit?
Yes, to accurately measure the capacitance, the capacitor must be removed from the circuit. Capacitors in a circuit could potentially interfere with the multimeter's reading.
How do I discharge a capacitor before measuring its capacitance?
Discharge the capacitor by placing a 20,000 Ω, 5-watt resistor across the terminals for about five seconds. Alternatively, technicians often use an insulated screwdriver to short the terminals, discharging the capacitor safely.
Why do I need to discharge the capacitor before measuring capacitance?
Discharging the capacitor ensures safety and prevents any stored electrical charge from interfering with your measurements or potentially causing a shock.
Can I use an analog multimeter to measure capacitance?
Yes, but for capacitance measurements, digital multimeters tend to provide more precise and clearer readings. Analog multimeters might require more manual adjustments and are less accurate for small values of capacitance.
What should I do if my multimeter doesn't display a steady value?
Ensure the capacitor is disconnected from the circuit, discharged, and that you're using the correct leads and settings. If your multimeter has a manual range, try adjusting it until the reading stabilizes.
Can I measure capacitance of electrolytic capacitors?
Yes, electrolytic capacitors can be measured with a multimeter, but note that they tend to have a wide tolerance range. Always ensure the electrolytic capacitor is discharged before measuring.
What is the unit of measurement for capacitance?
Capacitance is typically measured in farads (F), but for smaller components, microfarads (µF) are more commonly used.
What is the capacitor symbol on my multimeter?
The capacitor symbol on your multimeter looks like “–|(–”. This symbol is used to set the multimeter to capacitance measurement mode.
What’s the difference between microfarads (µF) and farads (F)?Microfarads (µF) are a smaller unit of capacitance, commonly used for measuring smaller capacitors. One microfarad is equal to one millionth of a farad (1 µF = 1 x 10^-6 F).
Can I measure the capacitance of a polarized capacitor with a multimeter?
Yes, you can measure a polarized capacitor with a multimeter, but it's important to connect the red lead to the positive terminal and the black lead to the negative terminal. Always ensure the capacitor is discharged before measuring.
Can I measure capacitance in a circuit with the power on?
No, always make sure the power is turned off before measuring capacitance. Measuring capacitance in a live circuit can be dangerous, potentially causing harm to you and damaging the multimeter.
Quiz
Question #1: What is the unit of measurement for capacitance?
Amperes
Ohms
Farads
Volts
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Question #2: Why must a capacitor be discharged before measuring its capacitance?
To ensure a stable reading
To prevent the multimeter from being damaged
To avoid electrical shock
To increase the accuracy of the measurement
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Question #3: What symbol should you look for on a multimeter when measuring capacitance?
Ω (Ohm symbol)
V (Voltage symbol)
A (Ampere symbol)
–|(– (Capacitor symbol)
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Question #4: What is the first step in preparing your multimeter to measure capacitance?
Set the multimeter to resistance mode
Set the multimeter to voltage mode
Plug the test leads into the correct ports
Turn on the power to the circuit
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Question #5: What should you do if your multimeter doesn't automatically range for capacitance?
Switch to a different multimeter
Set the range manually by adjusting the dial
Wait until the reading stabilizes
Measure capacitance again
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Question #6: What safety precaution should you take when measuring capacitance in a circuit?
Always wear gloves and safety glasses
Only use the multimeter’s auto range setting
Ensure the capacitor is in the circuit when measuring
Keep the capacitor connected to the circuit
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Question #7: What does the multimeter display when you measure capacitance?
Resistance value
A steady capacitance value
The voltage across the capacitor
The circuit’s current flow
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