The pitot tube produces a Differential pressure (DP) signal proportional to the square of the flow rate in accordance with Bernoulli's theorem. This signal has two components, the high pressure (HP) and the low pressure (LP).
When the fluid impacts the sensor, it creates a high pressure zone, greater than pipe static pressure, in front of the sensor. As the fluid moves past the sensor, it accelerates and a low pressure zone is created to the sides and rear of the senor. Multiple sensing ports are positioned in the high and low pressure zones and an averaged differential pressure is produced. The DP increases proportionally to the square of the velocity of the fluid.