Today I have successfully interfaced an MPX4115A pressure sensor to my Arduino board. The MPX4115A is an analog pressure sensor that outputs an analog voltage proportional with the pressure. The setup is the same as the previous one with the TMP102 temperature sensor; I just added the pressure sensor, a few decoupling capacitors and connected it to an analog input of the Arduino board.
Between 0° and 85° C the output voltage scales linearly with the pressure and the temperature error is negligible. Thus, calculating the pressure from the voltage is very simple according to the formula given in the data sheet. You can see the formula on the figure below.
A short video showing the MPX4115A pressure sensor and the TMP102 temperature sensor connected to the Arduino Duemilanove in action:
Watch the video on YouTube.
how can you have such stable pressure measurements each second?! The raspberry pi changes a lot of voltage. Its not always 5000 mV. in a second it can varie more than 20 mV and this can represent 1 hPa in pressure!!