The TruBlue 575 Baro is an absolute non–submersible pressure transducer. This unit provides local atmospheric pressure data that can be used to compensate one or more submerged, non–vented water level transducers. An absolute format measures all pressure applied to it including atmospheric. If submerged, it measures the atmospheric pressure plus pressure exerted by the column of water above the sensor. A level value can be arrived at using two absolute transducers–one submerged and one at ground level–subtracting atmospheric pressure from the submerged transducer measuring water pressure. A vented transducer provides a highly accurate water level reading with no further compensation required. This is accomplished via a vent tube that’s internal to the cable connected to the transducer. The vent tube exposes the sensor to the pressure of open atmosphere.