a flapper-nozzle system and Fig.shows a relationship between the output pneumatic signal and the distance between the flapper and the nozzle.
The diameter of the supply restriction 1 is 0.2-0.3 mm, whereas that of the nozzle 2 is 0.8 mm. The distance between the flapper 3 and the nozzle determines the output pressure in the chamber between them. This pressure is measured by the pressure gauge 4.
Small nozzle diameters increase gain, but also increase the danger of clogging. Large nozzle diameters increase the air consumption. The variation of the nozzle clearance by 0.04 mm gives the change in the output pressure from 20 to 100 kPa.