How to detect a short in a digital multimeter

Written by ryan long
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How to detect a short in a digital multimeter
Digital multimeters can be used to check for a short in a circuit in other digital multimeters. (digital multimeter 3 image by dinostock from Fotolia.com)

A digital multimeter is a great tool to determine whether there is a short in a given electrical system. It is also possible to use one multimeter to check another multimeter for a short. If your multimeter does not power on or is giving incorrect readings, you can check for a short circuit using a second multimeter to check the continuity or the resistance of the circuit. Checking the continuity will let you know if the multimeter is losing voltage, and testing the resistance will tell you if the circuit is correctly connected.

Skill level:
Easy

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Things you need

  • Digital multimeter
  • Test leads
  • Small Phillips or Torx screwdriver

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Instructions

  1. 1

    Switch on your digital multimeter and test it against a known circuit to make sure that it is in good working condition. If the multimeter is showing no reading, or an error in reading, test it one more time before continuing to Step 2

  2. 2

    Remove the back panel of your digital multimeter, using the small Phillips or Torx screwdriver. Visually inspect the circuit for obvious gaps or brown liquids. If gaps are detected or brown viscous liquid is detected, dispose of digital multimeter. If no obvious shorts are detected, proceed to Step 3.

  3. 3

    Set the second digital multimeter to its continuity mode to test for a short in the first digital multimeter. Touch the tips of the test probes on the second multimeter together to form a circuit. Your multimeter should beep audibly. This will indicate that a continuous circuit has been formed. If you do not hear a beep, make sure that the two probes are touching only on the metal portion. Also make sure that you are where you can hear the beep. If the multimeter does not beep, check to make sure that you are in the continuity mode as indicated by your user manual. Once you hear a beep after forming a circuit, you will be ready to test other circuits.

  4. 4

    Touch the test leads to a continuous circuit in the first multimeter at two points along the same wire. It does not matter where you place the test leads as continuity is not affected by polarity. Engage the digital multimeter. You should hear a beep. This indicates that there is not a short in the circuit. If you do not hear a beep this could indicate that you have a short in the circuit or that the circuit is disconnected at some point and the electrical charge put out by the multimeter is not making it all the way through the circuit. Most digital multimeters will show "OL," or "Open Loop," on their display. This indicates that there is lack of continuity in the circuit. This will also show up when the probes are not attached to the circuit and not touching one another.

  5. 5

    Touch the circuit again with the probes in a different area. If there is continuity you should hear a beep and the multimeter display will show a very small voltage. If you do not hear a beep, you will have to repair the circuit and check for continuity again.

Tips and warnings

  • Make sure that the power to the digital multimeter that you will test is off. The digital multimeter sends out voltage to read continuity, so if there is already a load on the system, it will throw off the results of the multimeter and may mask a potential short.

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