First Steps in Using a Multimeter
Part 3: Continuity Testing
Created on: 9 August 2012
A multimeter can be used for continuity testing. Continuity testing is done to check if there is a break in a wire or track on a circuit board (open circuit). Continuity testing can also check whether a wire or track is shorted to another wire or track (short circuit).
When the continuity function is used on a multimeter, the leads of the multimeter are placed on either end of a wire or track, the multimeter will make an audible sound if the wire or track is not broken, i.e. it is continuous. The multimeter acts as a buzzer circuit and the leads act as a switch. When the leads are touched together or on either ends of a conductor, the buzzer circuit is completed and the buzzer sounds.
The videos below show continuity testing on various items. A description of what is being done follows each video.
Basic Continuity Testing
Selecting the Continuity Function
To use the multimeter continuity function, switch the multimeter dial to the continuity test function. Touch the multimeter leads together and you should hear an audible "beep" sound. It is best to always touch the leads together and check for the beep before testing. This is done so that you know that the continuity function is working.
Performing the Continuity Test
In the video, a piece of stripboard is tested to see if a strip is unbroken and also to see that it is not shorted to one of the adjacent strips (one of the strips next to it).
A second multimeter is used to do the same stripboard test. This multimeter has a single dial setting for both the diode test and the continuity test.
A third multimeter (which is a cheap one) does not have an audible continuity tester. In this case, the diode tester is used and continuity is shown on the multimeter's display.
Wires from a cable are then tested for continuity.
Finally a printed circuit board (PCB) is tested for continuity of its tracks and to test that tracks are not shorted to each other. Normally every track would be tested, but only a few are checked in this video for demonstration purposes.
Continuity Testing on Breadboards
In this video, two different breadboards are tested for continuity. This shows that the two breadboards have different configurations of the horizontal rails. The first breadboard has horizontal rails that are split in the middle. The second breadboard has horizontal rails that run the full length of the breadboard.
Testing a Cable for Short Circuits
In this video, every wire in a cable is checked to see if it is shorted or not to every other wire in the cable. The wires at one end of the cable have been inserted into a breadboard to make testing easier.
To test every wire, the wires are measured in a pattern – put the first test lead on the first wire and the the other on every other wire in turn. Now move the first test lead to the second wire and check every other wire to the right of it with the second test lead, each in turn. Follow this pattern, moving the first test lead up by one wire each time as shown in the video.
Each short of one wire to another is marked on a piece of paper. At the end of the video, the other end of the cable is shown. The connections on the paper match the shorts at the end of the cable.