wasser@viking.DEC (John A. Wasser) (01/20/86)
Air pressure pushes against a piston that compresses a spring.
As the piston moves it pushes the calibrated rod out the top.
When the spring pressure matches the air pressure, the motion
stops (equilibrium). When the guage is removed, the spring
goes back but the rod is held in place by friction until pushed
back into the guage by hand.
Experiment: While the guage is still pressed to the tire,
push in on the rod. Do you feel the air pressure? Good.
-John A. Wasser
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