Technical Note — Logged Output


Created: ; updated: .


A logged port output is used to control an electrical device using the 12V supplied by a port output, either directly or via a 12V coil relay. The logged output can:

  • Provide manual or automatic control of a device, including automation based on water level and timers.
  • Show the current state of the output.
  • Provide history showing the output's on and off time.

Typical Observant Global display of a logged output that is controlling a pump:

Supported hardware

The device to be controlled should meet the following electrical specifications:

  • Nominal supply voltage: 12VDC
  • Maximum current draw: 500mA


When powering a device from a port output, keep in mind that this will eventually drain the field unit battery. If a device is to be powered for extended periods, or draws more than 100mA, it is strongly recommended that the field unit be provided with some manner of auxiliary power.

Specific hardware that has been used successfully in 240V pump control applications includes:

  • Manufacturer: Finder
  • Part number: 

Typical Application

Electric pump control


Connection to the field unit:

Refer to the wiring instructions accompanying the device and connect it to a field unit port output as follows:

Port pin



Output (1 or 2)


Red (typical: refer to the device datasheet)



Black (typical: refer to the device datasheet)


Many of the steps needed to install a field unit, modem, and other common devices can be seen on Vimeo at:


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