I try to connect an MPX5500DP to an Arduino Mega but it keeps giving me a reading of about 78PSI which correspond to around 5V even nothing is connected to the ports. I was expecting to get something close to 0 in that case. In don't really care about the noise so the sensor is directly connected the Arduino (1 Vout, 2 GRD, 3 Vcc) and do not use capacitors. I use sample sensors. I tried with 2 different sensors with the same result. Can they be damage on arrival? What can cause such behaviour to the sensors?