SOR 141 Differential Pressure Switch - Manual (Page 3)

Form 1307 (04.13) ©SOR Inc. 3/4
Calibration
This instrument may be calibrated as a pressure switch (low side vented); however, for
best performance, calibrate under simulated operating conditions.
The 131 has a static shift of -1 psi per 100 psi applied static. If the unit is calibrated without
static pressure applied, the set point should be adjusted to counter the actual static pressure.
To check the set point of a switch, monitor either the common (C) and normally open (NO)
or the common (C) and normally closed (NC) contacts for change of state. Connect the
process connection to a regulated hydraulic or pneumatic pressure source. Monitor with
an accurate pressure measuring standard. Slowly increase or decrease the pressure to
accurately capture the precise moment that the switch changes state. To assure the most
accurate and repeatable results, the switch must be tested in an identical manner each time
the calibration is checked.
Increasing Set Points
If the normal operating pressure is below the set point, then the pressure should be increased from 0
PSI up to the increasing set point and then back down to the reset point. Repeat this cycle
as necessary.
Decreasing Set Points
If the normal operating pressure is above the set point, then the calibration should be checked by first
pressurizing to the normal operating pressure, then reducing the pressure to the decreasing set point,
and then increasing the pressure to the reset point. Repeat this cycle as necessary.
To adjust pressure at which switch will operate, remove cover and tighten the hex head adjusting nut
with a 3/4” wrench to increase pressure; loosen to reduce pressure.
After calibration is complete, reinstall the cover with new gaskets as required by the
Maintenance instructions.
Switching Element
Calibration Scale
Adjusting Nut
The switching element has been
positioned with a dial indicator to
a tolerance of ±.002 inches. Do
not move this switching element!
Its position has nothing to do with
the set point adjustment. Any
movement can either render the
switch inoperative or cause the
switching element to be damaged
with overpressure.
Do not apply more than 300 psi
positive differential to the switch.
Do not apply a negative differential
of more than 10 psi.