Connectors

Mini Project

Testing Your Wire with a Multimeter

A multimeter is a handheld device that can measure ("meter") several different electrical properties ("multi"), depending on what mode it is set to.

One of its uses is to test whether there is a complete electrical connection between two points. This is helpful for checking whether a wire has been correctly constructed.

Step 1

A multimeter can be used to test for an unbroken electrical connection between two points. Something with no breaks is called "continuous", so this process is called "continuity" testing.

[STATIC IMAGES: Broken dotted line vs. Continuous line with labels]
Step 2

The continuity testing function of the multimeter tests for electrical continuity between two points that you touch the multimeter's leads to.

[Continuity test icon embedded in larger picture showing leads placed on opposite ends of wire, sound waves drawn coming out of multimeter]

Tip: If there is a continuous connection, the multimeter will make a beep sound, so the icon for this mode usually looks like a "sound waves" symbol.

No continuity test mode?
  • Some multimeters do not include this feature. If yours does not, follow the steps below but use the lowest-value Resistance test feature ([Ohm icon]) on your multimeter instead, and instead of a beep, look for a resistance value of zero or near zero to be shown on the screen.
SAFETY

The continuity tester does not work on circuits that have power running through them. Disconnect power from the portion of the circuit you are testing and test the parts individually. The multimeter may be damaged if you attempt to use this feature on a powered circuit.

Step 3

Plug the black lead of the multimeter into the COM terminal.

Step 4

Plug the red lead of the multimeter into the terminal with one of the following icons next to it:

[continuity testing icon, Ohm icon, Voltage icon, Diode icon [as images]]

Tip: The continuity test feature is electrically similar to several other multimeter functions, so it usually shares a plug and a spot on the dial with one of them. Different multimeters have it share with different modes.

Step 5

Turn the dial to the connectivity testing setting.

[IMAGE]
Step 6

Touch the metal parts of the multimeter leads together. The multimeter should make a sound while they are in contact (because the two leads are electrically connected to each other).

[IMAGE with sound wave markup]
No sound?
  • If no sound is played, check your connections and try again.
Step 7

Touch the two leads to the ends of the wire you want to test. If you hear a sound, it means that there is a continuous electrical path between those two points.

No sound?
  • This means there is no connection between the two points. Try to narrow down where the problem is by testing shorter portions of the wire. For instance, try touching the leads directly to the conductor in the wire -- if that part passes, then the problem must involve one of the connectors.

    [IMAGE showing subsection testing]
Unstable sound?
  • This either means you are trying to test for continuity across a component like an LED that cannot be tested using this mode (use Diode test mode instead), or it means the connection is loose.
  • The connector may be not be tightly crimped onto the wire conductor. Try tightening it.
  • You may also have damaged the conductor itself while attaching the connector -- for instance, you might have accidentally cut into the conductor while removing the wire insulation. This generally cannot be repaired, and you should remake that portion of the wire.
Step 8

Turn the multimeter dial back to the OFF position when you are done.

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