Hello Brian,
Indeed, for the use of pressure sensors in any other environments than dry air will require additional precautions and protection of the sensing element inside the pressure sensor:
Freescale's silicon pressure sensors are not compatible with oil, gas, petrol and water or water vapors, or chemicals.
After some working hours, maybe days the device would fail. The strain gauge and the electronic circuitry for calibration and compensation are protected by a nitride layer but the aluminum bonding pads which provide electrical connections between the leadframe and the gauge are not protected, in order to make the bonding feasible.
The complete die is also protected with a silicone gel. This gel is not fully hermetic, although we use much better gel for our newer types of pressure sensors, water or any other fluid can penetrate the gel and can reach the die.
I would like to recommend a possible solution to use our sensors in applications with other media than dry air:
Usually in a water measurement application, a head tube is used. This is simply a piece of tubing between the sensor and the container in which the water level or pressure needs to be measured.
Air is trapped in the tube and this isolates the sensor from the liquid water.
You cab refer to the following application note that would be worth to be considered in addition to the provided information.
AN3728 - Media Compatibility for IPS PRT Pressure Sensors
I hope this information will be useful for you. Please let me know if you need detailed information.
If I misunderstood your question, feel free to let me know. I will be glad to help.
Have a great day.
David Diaz.
