Using a Multimeter: Chapter 5
Content
So in this module, we will teach you how to use a multimeter to measure capacitance, capacitance measurement, unit of capacitance, how to measure capacitance, and what property of objects is best measured by their capacitance. Let’s jump right in.
Let’s talk about the Settings
Recall that capacitance refers to a system that stores an electric charge. Recall that farads is the unit of measurement for a capacitor. The image below shows a run capacitor used in HVAC systems. Let’s learn how to set your meter to measure capacitance. Capacitance measurement plays a major role in setting up a device.
Setting your device up
To measure capacitance, you will need to plug your leads into the correct ports on your multimeter.
Your red lead goes into the port marked with the "–|(–” symbol. This is the symbol for capacitance.
Your black lead will be plugged into the port marked with “COM”.
Before taking any measurements, you need to set your multimeter dial to measure capacitance.
Rotate the dial until it points at the "–|(–” symbol. See the image above for an example. All multimeters use the "–|(–” symbol for capacitance.
On some multimeters, you will need to use the yellow “function” key to set the multimeter to capacitance. Recall each dial position on a multimeter can have multiple measurements. If this is the case, press the yellow function key until the "–|(–” symbol appears on your display.
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.
Let’s learn how to discharge the capacitor before removing it from the circuit.
Once the power is turned off, you must discharge the capacitor.
Discharge the capacitor by touching the terminals with a 20,000 Ω, 5-watt resistor across the capacitor terminals for five seconds.
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.
How to measure capacitance using a multimeter?
Part One
Start by confirming that your black lead is plugged into the “COM” port and your red lead is plugged into the port marked "–|(–”.
Set your dial so that the arrow points to the "–|(–” symbol.
Turn off the power to the circuit.
Discharge the capacitor.
Remove the capacitor from the circuit.
Part Two
Turn off the power to the circuit.
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. Wear insulated gloves and safety glasses when handling any type of electrical equipment.
Part Three
Place one lead on each terminal of the capacitor. See the picture above.
In the picture, they are measuring a disconnected capacitor. Be sure that your hands do not touch the capacitor. This can interfere with the measurement.
As you touch the probes 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. Note the units displayed on the meter. For example, the meter might display microfarads.
Recall that 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.
Conclusion
It’s a wrap! Wasn’t that hard, was it? Learning how to set your meter to measure capacitance in the right way is very important in order to get an accurate measure. Be very sure to disconnect the capacitor from the circuit to avoid any risks. In this section, you learned how to measure the capacitance of a disconnected capacitor. In the next section, we will teach you how to measure continuity. By now, you will have a clear idea on unit of capacitance, how to measure capacitance and what property of objects is best measured by their capacitance.
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Answer the questions below!
Question #1:
"–|(–” is the universal symbol for capacitance on a multimeter.
True
False
Scroll down for the answer...
Answer: True
True, the "–|(–” symbol always represents capacitance on a multimeter. This includes the dial and port.
Question #2:
The capacitor has power after you turn off power to the circuit.
True
False
Scroll down for the answer...
Answer: True
True, the capacitor will keep a charge after the power is turned off. The capacitor is used to store electrical energy.
Question #3:
What should you do before removing a capacitor from the circuit:
Turn off the power
Discharge the capacitor
Wear all necessary safety gear
All of the above
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Answer: All of the above
Before you can measure capacitance you must turn off the power, discharge it, and wear safety gear.
Question #4:
Where should you place your leads on the component:
One lead on each terminal of the capacitor
Both leads on one terminal
Only use one lead on one terminal
All of the above
Scroll down for the answer...
Answer: One lead on each terminal of the capacitor
To measure capacitance you must place both leads on the entrance and exit of the component.
Question #5:
It is okay to hold a capacitor while you are measuring its capacitance.
True
False
Scroll down for the answer...
Answer: False
False, touching the component you are measuring can interfere with the multimeters ability to get an accurate reading.