CodeRage
Death by Magumba!
The sensors are stainless steel wet sensors with a 2 wire 4-20MA loop powered interface. I will have to lookup the make and model numbers and let you know what they were. What is interesting is no one has tried to make a liquid isolator with saran wrap sandwiched between plastic flanges. Glue sensor on one side and connect wet pressure on other side, if there are no air leaks on sensor it should work well. We use same principal to isolate hazardous chemicals from pressure devices in industry, but I have not used them for this low a pressure range before.
With a negative offset value applied to signal, density correction formula for temperature compensation, and time scaled SG factor, the freescale sensors should be fairly close most of the time.
Where I work we tried ssomething like this, it was to protect the sumbersable pressure sensor from lightning strikes. If I remember correctly these were 15 PSIg PITs. They worked okay but accuracy was always an issue. Any air in the system and temperature changes would hose the calibration. They ended up dropping the design.