The PS-1 Irrigation Pressure Switch adds irrigation water on/off data into the soil moisture data set. On/off data is a critical parameter to add to your system when using soil moisture sensors to monitor irrigation because it enables you to know your irrigation times.
The PS-1 registers ON at 5 PSI (=1.0 PSI). Because the sensor must be plumbed into the irrigation line, your data logger should be located where this can be done conveniently and cleanly.