High-Sensitivity Liquid Manometer Controlled by Personal Computer using a Laser Diode. Automatic Manometer under Fuzzy Control.

The problem of measuring small pressure differences with high accuracy has many engineering applications. These include, for instance, measurement of low flow velocities using Pitot tubes, and measurement of flow rate using nozzles. This paper describes an automatic liquid manometer that operates on the basis of a position-detecting system under fuzzy control. The manomater operates as follows. A laser beam is directed to the bottom of a float located inside a glass tube, and the spotlight is detected by a position-sensitive detector (PSD). The application of external pressure to the manometer causes the position of the spotlight on the float to change. The manomater moves the spotlight back into position by lifting a reservoir connected to the glass tube. The vertical displacement of the reservoir required to return the spotlight to its original position is equal to the pressure head applied. The system has been tested experimentally with good results.