A continuity test is done to determine whether a circuit is open or closed. For example, a wall switch is closed when it is turned to the "on" position and it is open when it is turned off. An open circuit cannot conduct electricity. A closed circuit has continuity.
This test should be done when current is NOT present. Always unplug the device or turn off the main circuit breaker before attempting a continuity test. Always test your test equipment for proper operation before use.
To test the continuity of a circuit requires the use of a multimeter (also called a multitester) or a continuity tester (a simple device that lights up to indicate continuity).
Set the multimeter to the ohm setting. The symbol for ohm is , the Greek letter omega. If there is more than one ohm setting, choose X1. An analog meter, like the one pictured below, uses a needle to indicate the measured value. A digital meter performs the same test functions as an analog meter, with the key difference being that a digital meter provides a numeric reading instead of using a needle.
Note that while the probes are not touching anything, the multimeter will indicate a reading of infinity. A reading of infinity means that the circuit is open. When you touch the two probes together, the reading changes to zero. A reading of zero indicates that the circuit is closed or complete. A complete circuit is one that can conduct electricity; an open circuit cannot.