dave-in-nj:
absolute pressure ? as referenced to ????
The internal sealed 2nd pressure port is evacuated to as perfect a vacuum as possible, so it's port is measuring applied pressure to the exposed port relative to absolute zero pressure.
the so-called one sided measurement is referenced ambient pressure.
Yes, the internal 2nd pressure port is exposed to ambient pressure but not available to the user, often called a gauge pressure measurement.
put it on a plane or in a barometric chamber and in both cases it will read zero.put it on a plane and connect it to the outside of the plane and the pressurized cabin will only effect one side of the sensor. odd'ly, the side NOT connected to the tubing.
all a differential pressure device has is a second connection port.
you put that sensor in a waterproof box, add a house for the box area and a second one to the connection and you have created a differential pressure sensor.
a Bordon tube is a perfect example. the atmosphere in which the device is placed is the reference pressure. the tubing is connected to a separate environment.