Before testing your circuits, you must make sure that your meter is working properly. Any malfunction gives you incorrect testing results — and you may not even realize it.
To test your multimeter, follow these steps:
Check the cleanliness of the test probes
Make sure that the test probes at the end of the test leads are clean. Dirty or corroded test probes can cause inaccurate results. Use an electronic contact cleaner to clean both ends of the test probes and, if necessary, the connectors on the meter.
Turn on the meter
Turn on the meter and dial it to the Ohms (Ω) setting. If the meter isn’t auto-ranging, set it to low ohms.
Plug the test probes
Plug both test probes into the proper connectors of the meter and then touch the ends of the two probes together. Avoid touching the ends of the metal test probes with your fingers while you’re performing the meter test. The natural resistance of your body can throw off the accuracy of the meter.
The meter should read 0 (zero) ohms or very close to it
If your meter doesn’t have an auto-zero feature, press the Adjust (or Zero Adjust) button. On analog meters, rotate the Zero Adjust knob until the needle reads 0 (zero). Keep the test probes in contact and wait for a second or two for the meter to set itself to zero.
Recheck the dial setting
If you don’t get any response at all from the meter when you touch the test probes together, recheck the dial setting of the meter. Nothing happens if you have the meter set to register voltage or current. If you make sure that the meter has the right settings and it still doesn’t respond, you may have faulty test leads. If necessary, repair or replace any bad test leads with a new set. You can consider the meter calibrated when it reads zero ohms with the test probes shorted together (held together so they’re touching each other). Do this test each time you use your meter, especially if you turn off the meter between tests. If your meter has a Continuity setting, don’t use it to zero-adjust (calibrate) the meter.
The tone may sound when the meter reads a few ohms, so it doesn’t give you the accuracy you need. Recalibrate the multimeter using the Ohms setting, and not the Continuity setting, to ensure proper operation.