1. Depth Sensing There is a linear relationship between pressure and depth. The following is the mathematical representation of the relationship: ΔP = γh –ΔP  Pressure Difference –γ  Specific Weight of Liquid –h  Change In Elevation

2. Freescale MPX4250AP Ported Pressure Sensor

3. Pressure Sensor Tests The data collected from the pool test shows that the sensor has a linear output of about 62mV per foot. This gives us a full scale voltage of about 4.25 V which provides an excellent resolution to feed into the A2D converter on the HC08.