Using a Multimeter: Chapter 4
In this module, we will teach you how to use your multimeter to measure resistance. Skip to quiz!
1. Settings
To measure resistance, you will need to connect your leads into the correct ports on your multimeter. Your red lead goes into the port marked with a “Ω”. 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 resistance. Rotate the dial on your multimeter until the dial is pointed at the “Ω” symbol.
On all multimeters, “Ω” is the symbol for resistance. The “Ω” symbol stands for ohms, the unit of measurement for resistance.
To measure a component’s resistance, the component must be disconnected from the circuit. Before disconnecting the component, turn the power off. Treat the circuit as if it still has power until you measure the voltage. If there is 0 voltage, then you can continue.
The multimeter measures resistance by running a small test voltage through the component. When the component has power running through it, the multimeter cannot read the test voltage. This prevents the meter from accurately reading resistance.
2. How to measure resistance using a multimeter?
Now that you know how to setup your multimeter, we will go through the process of measuring resistance.
Confirm that your black lead is connected to the “COM” port and your red lead is connected to the port marked “Ω”. Confirm that your dial is set to the “Ω” symbol. Place the disconnected component away from the circuit.
To measure resistance, you need to place your leads on the positive and negative terminals of the component. In the picture, we are measuring the resistance of a fuse. Notice that one lead is touching the positive end of the fuse. The other lead is touching the negative end.
When your leads are touching the component, you will see a value appear on the multimeter display. This is your resistance measurement. The display will also show the units of the measurement. For example, your display may read 200Ω.
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 to get an accurate result. Do this by slowly turning the dial to a lower range setting. Stop once you have an accurate measurement.
If your multimeter is Auto ranging, the multimeter will automatically change the range. By automatically changing the range, your multimeter shows you the most precise value.
For example, look at the V measurements on this non auto ranging meter. You can see that there are values ranging from 2 to 1000 volts. If your meter dial is pointed at 1000, you are measuring in the range of 0-1000V. If you change the dial to point at 2, you are measuring in the range of 0-2V.
The range determines the accuracy of your measurement. If you measure a 2Ω resistance at a 2000Ω range, your precision will be very bad. By decreasing the range, you will get a more accurate result and more decimal places on the measurement.
3. Conclusion
In this section, you learned how to measure the resistance of a component. In the next section, we will teach you how to measure capacitance.
Question #1: “Ω” is the universal symbol for resistance on a multimeter.
True
False
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Answer: True
True, the “Ω” symbol always represents resistance on a multimeter. This includes the dial and port.
Question #2: Your multimeter measures resistance by running a small test voltage through the component:
True
False
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Answer: True
True, the multimeter sends a small voltage through the component. Having the power on while measuring resistance interferes with the multimeters ability to read this test voltage.
Question #3: Before measuring resistance, you must:
Disconnect the component from the circuit
Set your multimeter dial to “Ω”
Connect your leads to the “Ω” and COM ports
All of the above
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Answer: All of the above
Before you can measure resistance you must disconnect the component, set your dial, and attach your leads.
Question #4: Where should you place your leads on the component:
One lead on the positive side and one lead on the negative
Both leads on the negative side
Only use one lead on the component
All of the above
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Answer: One lead on the positive side and one lead on the negative
To measure resistance you must place both leads on the positive and negative ends of the component.
Question #5: It is okay to hold a component while measuring resistance.
True
False
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Answer: False
False, touching the component you are measuring can interfere with the multimeters ability to get an accurate reading.