dc42:
That's an interesting device, however the following excerpt from the datasheet would concern me:"The MPX2010 series pressure sensor operating characteristics and internal reliability and qualification tests are based on use of dry air as the pressure media. Media other than dry air may have adverse effects on sensor performance and long term reliability".
Allowing water into the device doesn't sound like a good idea to me. It would be possible to have the pressure sensor connected to an air-filled tube, with the other end of the tube at the bottom of the tank; but in this arrangement, the air is always going to be at 100% relative humidity, so it's hardly dry.
Or maybe you have an ingenious arrangement that keeps the sensor in dry air all the time?
Although this device has been used by many it seems for the same application, yes you do need to keep it dry using a trapped column of air. The RH didn't bother me as the application notes suggest using it for Application Examples • Respiratory Diagnostics, doubt that 0%RH either. What exactly is considered "dry air". Anyway I placed a loop in the tube filled with a oil. Naturally the oil can move in the loop. So the tube goes from the bottom of the tank, loop round then out the top of the tank. The loop prevents the oil just dropping out the bottom of the tube.
If you have access to an outlet pipe at the bottom or the bottom of the tank that's better as you won't have diffusion problems with the air mixing with the water and the water moving up the tube giving lower tank level readings.
Anyway, It's worked for me and others so I'm happy with any risk of blowing the sensor. Plus I ordered 2 samples from freescale so I have a spare.