Continuity tester

[1] The tester consists of an indicator in series with a source of electrical power - normally a battery, terminating in two test leads.

For situations where continuity testing must be done on high resistance circuits, or where delicate conductors and sensitive components that might be damaged by excessive current are present, a low voltage, low current device must be used.

For example, vibration-induced problems in automobile wiring can be extremely difficult to detect because a short or open is not maintained long enough for a standard tester to respond.

A more complex device, it detects intermittent opens and shorts as well as steady-state conditions.

[4] These devices contain a fast acting electronic switch (generally a Schmitt trigger) forming a gated astable oscillator which detects and locks (latches) the indicator on an intermittent condition with a duration of less than a millisecond.