Hi, For some background:
http://www.bapihvac.com/content/uploads/2010/07/Understanding-4-20-mA-Current_Loops.pdf
This is an Industrial Control standard. It is fairly resistant to noise, is insensitive to length of cable, and since the current is always > 0 you can tell if there is an open or shorted cable.
You can use it by connecting the device from some voltage like 9 or 12 V DC (Greater than the 8V minimum) and to a resistor to ground. Pick the resistor to have a voltage drop less than 5V at the maximum pressure you want to measure.
- Say that is 20mA (Max pressure). So R=E/I so R=5/.02 = 250 ohms. Do a little math with the Device data sheet and the 0..1023 Arduino measurement result and you have the pressure.
-- NOTE that there is a 4ma value to subtract in your math so that 4ma = 0 pressure.
Consider that the current will vary from 4 to 20 ma, and that range represents the pressure range.
4-20ma devices are usually expensive, but in surplus they can be a nice choice. Many types of sensors are made that put out this type of signal.
Let us know how you make out...
Regards, Terry King
terry@yourduino.com