When using DSI pressure transmitters, it is necessary to use an Ambient Pressure Reference.  DSI’s ambient pressure monitors report the absolute pressure measured in the room where it is placed.  However, the ambient pressure monitors do not adjust to changes in altitude.  Below are considerations for laboratories with elevations above sea level.

Some barometers are calibrated to report barometric pressure adjusted to a sea level reading, which is what the weather service reports.  This allows the weather service to report and compare barometric pressure differences with no regard to the elevation of the reporting station.  DSI’s ambient pressure monitors report the absolute pressure measured in the lab, which will vary with elevation of the lab.  This reading is lower than that given by the weather service due to the elevation above sea level.

For comparison to weather service and/or sea level adjusted barometers, the differences are summarized in the following table: