# How To Use A Multimeter

1. ## 步骤 1 Testing Continuity

• A continuity test tells us whether two things are electrically connected: if something is continuous, an electric current can flow freely from one end to the other.

• If there's no continuity, it means there is a break somewhere in the circuit. This could indicate anything from a blown fuse or bad solder joint to an incorrectly wired circuit.

• Continuity is one of the most useful tests for electronics repair.

2. ## 步骤 2

• To begin, make sure no current is running through the circuit or component you want to test. Switch it off, unplug it from the wall, and remove any batteries.

• Plug the black probe into the COM port on your multimeter.

• Plug the red probe into the port labeled with a V symbol (in this case, the right port).

3. ## 步骤 3

• Switch on your multimeter, and set the dial to continuity mode (indicated by an icon that looks like a sound wave).

• Not all multimeters have a dedicated continuity mode. If yours doesn’t, that’s okay! Skip to step 6 for an alternate way to perform a continuity test.

4. ## 步骤 4

• The multimeter tests continuity by sending a little current through one probe, and checking whether the other probe receives it.

• If the probes are connected—either by a continuous circuit, or by touching each other directly—the test current flows through. The screen displays a value of zero (or near zero), and the multimeter beeps. Continuity!

• If the test current isn't detected, it means there's no continuity. The screen will display 1 or OL (open loop).

5. ## 步骤 5

• To complete your continuity test, place one probe at each end of the circuit or component you want to test.

• As before, if your circuit is continuous, the screen displays a value of zero (or near zero), and the multimeter beeps.

• If the screen displays 1 or OL (open loop), there's no continuity—that is, there's no path for electric current to flow from one probe to the other.

• Continuity is non-directional, meaning it doesn't matter which probe goes where. But there are exceptions—for instance, if there's a diode in your circuit. A diode is like a one-way valve for electricity, meaning it will show continuity in one direction, but not in the other.

• To check for this, reverse what the probes are touching and check for continuity. If the multimeter shows continuity, then it's possibly a diode.

6. ## 步骤 6 Test for continuity (alternate method)

• If your multimeter doesn't have a dedicated continuity test mode, you can still perform a continuity test.

• Turn the dial to the resistance mode.

• If your multimeter has manual ranging, set the resistance to the lowest setting.

• Resistance is measured in ohms, indicated by the symbol Ω.

7. ## 步骤 7

• In this mode, the multimeter sends a little current through one probe, and measures what (if anything) is received by the other probe.

• If the probes are connected—either by a continuous circuit, or by touching each other directly—the test current flows through. The screen displays a value of zero (or near zero—in this case, 0.8). Very low resistance is another way of saying that we have continuity.

• If no current is detected, it means there's no continuity. The screen will display 1 or OL (open loop).

8. ## 步骤 8

• To complete your continuity test, place one probe at each end of the circuit or component you want to test.

• It doesn't matter which probe goes where; continuity is non-directional.

• As before, if your circuit is continuous, the screen displays a value of zero (or near zero).

• If the screen displays 1 or OL (open loop), there's no continuity—that is, there's no path for electric current to flow from one probe to the other.

9. ## 步骤 9 Measuring voltage

• The next four steps will show you how to measure voltage.

• Plug the black probe into the COM port on your multimeter.

• Plug the red probe into the port labeled with a V symbol (in this case, the right port).

10. ## 步骤 10

• Switch on your multimeter, and set the dial to DC voltage mode (indicated by a V with a straight line, or the symbol ⎓).

• Virtually all consumer electronic devices run on DC voltage. AC voltage—the kind that runs through the lines to your house—is considerably more dangerous, and beyond the scope of this guide.

• Your multimeter may be auto-ranging or manual ranging. An auto-ranging multimeter (such as the iFixit multimeter) will automatically determine the best measuring range. All you have to do is set what kind of measurement you want to take.

• If your multimeter is manual ranging, you'll also need to set the correct range for the voltage you expect to measure.

• Each setting on the dial lists the maximum voltage it can measure. So for example, if you expect to measure more than 2 volts but less than 20, use the 20 volt setting.

11. ## 步骤 11 Auto-ranging voltage measurement

• Place the red probe on the positive terminal, and the black probe on the negative terminal. The multimeter will display the measured voltage.

• Reversing the probes won't do any harm; it just gives a negative reading.

• Skip the next step, which describes how to measure voltage using manual ranging multimeters.

12. ## 步骤 12 Manual ranging voltage measurement

• Follow this step to measure voltage with a manual ranging multimeter.

• Place the red probe on the positive terminal, and the black probe on the negative terminal.

• If your range was set too high, you may not get a very precise reading. Here the multimeter reads 9 volts. That's fine, but we can turn the dial to a lower range to get a more precise.

• If you set the range too low, the multimeter simply reads 1 or OL, indicating that it is overloaded or out of range. This won't hurt the multimeter, but we need to set the dial to a higher range.

• With the range set correctly, we get a reading of 9.42 volts.

• Reversing the probes won't do any harm; it just gives us a negative reading.

13. ## 步骤 13 Measuring resistance

• The next three steps will show you how to measure resistance with your multimeter.

• To begin, make sure no current is running through the circuit or component you want to measure. Switch it off, unplug it from the wall, and remove any batteries.

• Remember that you'll be measuring the resistance of the entire circuit. If you want to measure an individual component such as a resistor, measure it by itself—not with it soldered in place!

• Plug the black probe into the COM port on your multimeter.

• Plug the red probe into the port labeled with an Ω symbol (in this case, the right port).

14. ## 步骤 14

• Switch on your multimeter, and set the dial to resistance mode.

• Resistance is measured in ohms, indicated by the Ω symbol.

• The iFixit multimeter is auto-ranging, meaning it will automatically determine the best measuring range.

• If your multimeter is manual ranging, you will need to set the correct range for the resistance you expect to measure. If you're not sure, start with the highest setting.

15. ## 步骤 15

• Place one probe at each end of the circuit or component you want to measure.

• It doesn't matter which probe goes where; resistance is non-directional.

• If your multimeter is manual ranging:

• If your multimeter reads close to zero, the range is set too high for a good measurement. Turn the dial to a lower resistance range.

• If you set the range too low, the multimeter simply reads 1 or OL, indicating that it is overloaded or out of range. This won't hurt the multimeter, but we need to set the dial to a higher range.

• The other possibility is that the circuit or component you are measuring doesn't have continuity—that is, it has infinite resistance. A non continuous circuit will always read 1 or OL on a resistance test.

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### 134条评论

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