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, high pressure (HP) and low pressure (LP).

DP= HP-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 sensor. 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.