The limit of
deviation from the set point of a pressure or vacuum switch. It
is usually defined in either pounds per square inch, or percentage
of full scale.
between the set point and reset point.
between the increasing and decreasing readings when the switch is
operated between set point and reset point.
Opens or closes
an electrical circuit in response to movement from the pressure
or vacuum sensing element. Single pole, double throw (SPDT) snap
action switches are standard, may be used as single pole, single
throw (SPST). NO/NC circuitry is selectable, but must be specified
at order placement.
in pressure or vacuum switch response to increasing and decreasing
pressure or vacuum.
- Normally Closed
through the switch until broken by a pressure or vacuum change.
- Normally Open
No current flows
through the switch until contact by a pressure or vacuum change
A pressure scale
based on PSIA "0" or a perfect vacuum.
immediately surrounding a pressure switch, usually but not necessarily,
atmospheric gauge pressure.
caused by the actual weight of the earth's atmosphere. At sea level
atmospheric pressure equals 14.7 psi, 30 inches of mercury or 408
inches of water, above absolute "0" ("0" PSI).
difference between two pressures. The term is correctly applied
to "differential" pressure switches that detect variations
in a fixed difference between two pressures.
pressure used as zero reference point so there is no compensation
for changes in barometric pressure.
which can be applied to a pressure switch without causing irreparable
damage. It is usually 150% of the pressure sensing element's rated
maximum system pressure.
pressure level not including surges or spikes.
- Pressure Sensing
of the pressure switch that moves with a change in system fluid
- Pressure Switch
that converts a pressure change to an electrical function.
of the switch to actuate repeatedly at the desired set point within
- Reset Point
After the pressure
has reached set point and operated the electrical switch, it must
return to the reset point before the electrical switch returns to
its original position.
- Set Point
The exact point
at which the electrical switching element functions. This is generally
expressed in PSI, inches of mercury or PSIA.
less than ambient pressure using ambient pressure as a reference.