Gas at the higher pressure is delivered into the lower chamber of the gauge where it applies a force on the bottom of bellows 1. Gas at the lower pressure is delivered into the bellows. The difference in the pressures acting on the bottom of the bellows is counterbalanced by spring 2 whose number of active coils can be varied by turning insert 3. Owing to the pressure difference, the bellows is compressed and, by means of lever 4, it turns shaft 6. This shaft is brought out through seal 5 and is linked to a mechanism which operates the shutter of the regulator. The instrument is zeroed by adjusting screw 7. The motion of the bellows is restricted by sleeve 8 and by boss a of the gauge housing.
$4080$EHP,M$