SM07-006-0
Page 3/(4 Blank)
DESCRIPTION
The low pressure indicating switch is designed to
provide a warning to the operator that one or both air
systems are at a low pressure. The switch is electri-
cally connected to a buzzer and a red indicator warn-
ing light. The switch has a die cast body with a nylon
cover, and employs a spring loaded O-ring diaphragm
and piston. A gasket is used between the cover and
body. The switch is provided with electrical contacts
and a single terminal from connection to the electri-
cal system. The contacts remain closed by spring
force until the air pressure below the diaphragm is
great enough to overcome the spring force. This
pressure setting is approximately 75 psi (517 kPa/
5.17 bar) and should be marked on a label affixed to
the valve body.
THEORY OF OPERATION
When air pressure at the supply port and under the
75 psi (517 kPa/5. 17 bar), the spring exerts a force
diaphragm is above 75 psi (517 kPa/5.17 bar), the
which is greater than the force exerted by the air
electrical contacts remain open because the force
pressure below the diaphragm. This causes the di-
exerted by air pressure underneath the diaphragm
aphragm and piston to move and allow the electrical
overcomes the force exerted by the spring above the
contacts to close. This completes or closes the elec-
diaphragm.
trical circuit to the warning buzzer and the indicator
light.
When air pressure below the diaphragm drops below
