October 4, 2013

Using your multimeter: Continuity Test

One of the most basic uses of a multimeter is to test if there is continuity in a circuit. Testing for continuity means to verify if a circuit, wire or fuse is complete with no open. A switch in the off position will be "open" and no continuity.  A switch in the on position "closed" and has continuity between its contacts.

Digital Multimeter

Audible continuity means the multimeter produces a tone that you can hear when a circuit is complete.  Audible continuity testing is very handy since it allows you keep your eyes on your hands and the circuit you are testing.  You can hear if continuity is present without looking at the meter.

Never try to test continuity with on a circuit that is energized.  The meter may be damaged and you risk injury.

The basic procedure for a continuity test:
  1. Make sure the circuit is not energized.
  2. Set your multimeter to continuity test.
  3. Touch the two probes together.  You should hear a tone which indicates the continuity test is working.  If you don't hear a tone then the multimeter you must stop and resolve the issue. Likely problems: the meter is not set to continuity test, the meter's fuse is blown, or the multimeter is damaged.
  4. Place the two probes across the two conductor you are testing for continuity.
  5. If you hear a tone, continuity is present.  If you don't hear a tone then the circuit is "open" and there is no continuity.
Typical uses in amateur radio:
  • Confirm there is no electrical connection (short) between the center conductor and shield on a piece of coax
  • Confirm that there is an electrical connection between the center conductors on both ends of a length of coax
  • Confirm that there is an electrical connection between the shield on one end to the other end on a length of coax
  • Testing DC power cable assemblies.
  • Testing fuses
  • Test if a switch is working properly
  • Test if the multimeter's own internal fuse has been blown
There are an endless number of uses for a basic continuity test and it is a great feature to have in a multimeter and on your bench.

Good DX and 73, NJ2X

Check out our other related articles on NJ2X.COM:
Quick Guide To Common Multimeter Symbols and Abbreviations

© Michael W. Maher and NJ2X.COM, 2013. Unauthorized use and/or duplication of this material without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Michael W. Maher and NJ2X.COM with appropriate and specific direction to the original content.