Flapper - Nozzle system (323)
The set up helps in understanding conversion of mechanical motion to pressure signal. It consists of flapper - nozzle mechanism, Dial gauge indicator, pressure gauges and air filter regulator. A regulated supply of pressure, usually over 20 psig, provides a source of air through the restriction.
The nozzle is open at the end where the gap exists between the nozzle and flapper, and air escapes in this region.