Wiring diagram for contact monitoring

Switch contact status is effortless when using a portable self-contained Data Logger from ACR – simply wire two terminals without an external power supply.

ACR Temperature Data Loggers can be used to monitor dry-contacts either normally open or closed. These can be part of existing circuits as long as voltage is not applied to the inputs hence the term dry – this can be a separate pole on a switch or relay. For applications where only a voltage signal is available, use an interposing relay to isolate the input. TrendReader software produces a graph showing the duty cycle of the contact either on or off over the sampling interval. In normal mode, a contact state change can be detected once every 8 seconds. In the SmartReader Plus Fast Read mode, a state change can be detected once every 25msec. For momentary contact closure such as a pushbutton switch or rate counter, it is recommeded to use a Pulse Input Data Logger to capture every event.


  • Easy Installation – Any Contact Type
  • No External Power Required
  • Software Shows Duty Cycle