Most moisture detecting switches are instruments of the float type or conductivity type. Float types are adapted to actuate at very low levels. Conductivity types may consist of point sensitive probes located very close to the bottom of a low point or sump where water will collect, or they may be ribbons or strips with wires separated by a non-conductive material, such that when any portion of the ribbon is exposed to liquid moisture, the electrical circuit is completed and the switch mechanism activates. Current Switches Current sensing relays are used in DDC systems to monitor the status of electrical devices. The devices typically have one or more adjustable current set points.
Current switches can detect broken fan belts if properly adjusted.
Current relays can also be used for phase monitoring.