I selected a pressure sensor from Freescale Semiconductor wide range. I picked up one with the following specifications: integrated, absolute measure, 0 to 250 kPa.
It comes in various form-factors, either small outline / surface mount package or unibody package, with or without a nose.
The manufacturer provides an excellent application note Understanding Pressure and Pressure Measurement. The sensor provides a voltage linear to the pressure measured. So implementation is rather easy.
After extensive testing with the Arduino board, I went into packing the sensor into a fischertechnik block so I could use it with my industrial models.
Pressure Sensor Tests
I carried out some tests with the pressure sensor on an Arduino board.
How many measures per second? What is the reactivity?
The sensor is powered by a fischertechnik battery. Signal is sent to A0 analog input.
When used, SD card is connected to TX → 1 pin.
I guess the hardware has a consequence on the measures:
Measures rate and reactivity are good enough for my fischertechnik industrial models!
Pressure Sensor Mathematical Model
I've built a very basic model based on the ideal gas law (reference):
PV = nRT
I considered R and T as constants and took 1 atm close to 100 kPa. Actually, 1 atm = 101,33 kPa instead of 1 atm ≈ 100 kPA.
I measured the volumes of the tank and the piston rods, with and without spring.
I conducted two series of measures:
As always, the model and the measures are provided below. It's always nice to see that Nature obeys physical laws!
Results and Interpretation
The findings are:
Now, how to build a smart pressure management?