Work 1 to be checked is placed on base 2, and above the work, with a certain clearance, measuring head 3 is rigidly mounted. This head is connected by tube 4 to measuring chamber 6 into which compressed air enters through small orifice (restrictor) b. Tube 7, immersed in water chamber 8, serves to maintain constant air pressure. Surplus air is evolved as bubbles. Manometer 5 is connected to measuring chamber 6 and to water chamber 8. The difference in height h between the levels in water chamber 8 and manometer 5 depends upon the clearance a between the metering orifice of measuring head 3 and work 1. The manometer tube is graduated in units of deviation of the size of the work from the specified value.
$3730$SHP,M$