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PSW-141 Series
Low Differential Pressure Switch
INSTALLATION OF PSW-141 PRESSURE
SWITCH
NOTE:
Each switch is calibrated in the vertical
positionꢀ It is recommended the switch be
mounted in the vertical position, as viewed
in Figure 1ꢀ Any adjustments to the
setpoint or deadband should be performed
with the instrument in the mounted positionꢀ
The PSW-141 differential pressure switch is suitable for clean air
or inert gas applicationsꢀ If dust is present, a small in-line filter is
recommended to insure long, trouble-free operationꢀ The normal
operating temperature range is from 0°C to 45°C (32°F to 115°F),
and the normal humidity range from 10% to 90% RꢀHꢀ
Figure 1
Air connections are by means of 3/16” (4ꢀ75mm) barbed fittings
suitable for 1/4” OꢀDꢀ polyethylene tubing (6mm), 1/8” IꢀDꢀ Tygon or
polyurethane tubing (3 - 4mm)ꢀ
The two mounting holes are 0ꢀ19” (4ꢀ8mm) in diameter and are
suitable for #8 or #10 mounting screwsꢀ
Ohmmeter Output: Relay
Common and Normally
Closed
Rising
Pressure
Electrical connections are by means of 3/8” terminal strips with #6
screwsꢀ
Spacing between mounting holes: 4ꢀ75 inches (121 mm)ꢀ
Care should be taken not to exceed the maximum overpressureꢀ
Falling
Pressure
Pressure
No Applied
Pressure
Full Pressure
Maximum Safe Momentary Overpressure Table
Closed (0)
Open (OL)
Open (OL)
Closed (0)
Range
Overpressure
English
Metric
English
Metric
0.1" to 1.0" H2O
2.0" to 10.0" H2O
11" H2O to 5 PSID
6 PSID to 15 PSID
16 PSID to 30 PSID
25 to 250 Pa
0.5 to 2.5 kPa
2.7 to 35 kPa
40 to 100 kPa
110 to 200 kPa
8" H2O
5 PSID
20 PSID
30 PSID
60 PSID
2 kPa
35 kPa
140 kPa
200 kPa
420 kPa
Table 2
Setpoint Adjustment
Apply full pressure, (or the pressure at which the setpoint is to
activate)ꢀ Rotate the 20 turn Setpoint potentiometer, until the ohm-
meter changes stateꢀ Turn clockwise to increase the set point and
counter-clockwise to decrease the set point
Power consumption is ꢀ35 W for the DC powered units,
1ꢀ70 W for the 24 Vac and 1ꢀ90 W for the 120 Vacꢀ
The power supply leads are connected to the two leftmost termi-
nals (terminals 1 and 2) on the terminal stripꢀ The relay terminals
are accessed across terminals 3, 4, and 5, refer to Figure 1ꢀ
Slowly decrease the pressure until the relay deactivatesꢀ The dif-
ference between the pressure at which the relay deactivates and
the pressure at which the relay activates is the deadbandꢀ If more
deadband is required, turn the deadband potentiometer and re-
peat the previous stepsꢀ Adjustment of the deadband will have a
slight effect on the set point, therefore it will be necessary to re-
peat these steps several timesꢀ
The pressure switch comes with Setpoint and Deadband Adjust-
mentsꢀ These are adjusted at the factory to activate on either fall-
ing or rising pressureꢀ The setpoint is factory set to activate at the
maximum pressureꢀ The deadband is set to 5% of the maximum
pressureꢀ
RELAY SPECIFICATIONS
The output of the SPDT (1 Form C) relay contact is rated at:
5A @ 30 VDC/120 VAC Resisitive
SETPOINT/DEADBAND ADJUSTMENT PROCEDURE
4A @ 240 VAC Resistive
The set point and deadband are field adjustable so long as an
accurate pressure source is available and a qualified technician
performs the adjustmentsꢀ The low pressure switches are extremely
sensitive to sudden pressure changesꢀ
Gold-plated relay contactsꢀ
Electrical life expectancy: 100 x 103 opsꢀ minimum @ 5A
Isolation between coil and contacts: 2000 VAC 1 minute
Maximum switched power: 600 VA (AC) or 120 W (DC)
Operate Time: 8 ms, max (Excluding Bounce)
Release Time: 4 ms, max (Excluding Bounce)
To gain access to the Setpoint or Deadband potentiometers re-
move the black hole plugs above the Setpoint and Deadband la-
bels, located on the top left of the instrumentꢀ To access either
potentiometer use a slotted 3/32” screw driverꢀ
Connect the switch to its appropriate power supplyꢀ
Connect an ohmmeter to the relay contacts “common” and “nor-
mally closed” or “normally open”ꢀ If a switch was ordered with a
relay activated on “Rising Pressure” and the ohmmeter terminals
are connected to the “normally closed” and “common” of the relay,
with no pressure applied, the ohmmeter should read 0 or closed,
refer to Table 2ꢀ
Deadband Adjustment
To set the deadband to zero, turn the Deadband potentiometer
fully counter-clockwise ꢀ Zero deadband will cause the relay to
chatterꢀ It is recommended that some amount of deadband be
usedꢀ Turning the deadband potentiometer clockwise increases
the deadbandꢀ
PSW-141 Series
M-3488 / 0011
WARRANTY/DIS CLAIMER
OMEGA ENGINEERING, INC. warrants this unit to be free of defects in m aterials and workm anship for a
period of 1 3 m o n t h s from date of purchase. OMEGA’s Warranty adds an additional one (1) m onth grace
period to the norm al o n e (1 ) ye a r p ro d u c t w a rra n t y to cover handling and shipping tim e. This
ensures that OMEGA’s custom ers receive m axim um coverage on each product.
If the unit m alfunctions, it m ust be returned to the factory for evaluation. OMEGA’s Custom er Service
Departm ent will issue an Authorized Return (AR) num ber im m ediately upon phone or written request.
Upon exam ination by OMEGA, if the unit is found to be defective, it will be repaired or replaced at no
charge. OMEGA’s WARRANTY does not apply to defects resulting from any action of the purchaser,
including but not lim ited to m ishandling, im proper interfacing, operation outside of design lim its,
im proper repair, or unauthorized m odification. This WARRANTY is VOID if the unit shows evidence of
having been tampered with or shows evidence of having been damaged as a result of excessive corrosion;
or current, heat, m oisture or vibration; im proper specification; m isapplication; m isuse or other operating
conditions outside of OMEGA’s control. Com ponents which wear are not warranted, including but not
lim ited to contact points, fuses, and triacs.
OMEGA is p le a s e d t o o f fe r s u g g e s t io n s o n t h e u s e o f it s v a rio u s p r o d u c t s . Ho w e ve r,
OMEGA neither assum es responsibility for any om issions or errors nor assum es liability for any
dam ages that result from the use of its products in accordance w ith inform ation provided by
OMEGA, either verbal or w ritten. OMEGA w arrants only that the parts m anufactured by it w ill be
a s s p e c if ie d a n d f r e e o f d e f e c t s . O M EG A M A KES N O O THER WA RRA N TIES O R
REPRESENTATIONS OF ANY KIND WHATSOEVER, EXPRESS OR IMPLIED, EXCEPT THAT OF TITLE,
AND ALL IMPLIED WARRANTIES INCLUDING ANY WARRANTY OF MERCHANTABILITY AND FIT-
N ES S FO R A P A RTIC U LA R P U RP O S E A RE HEREBY D IS C LA IM ED . LIM ITATIO N O F
LIABILITY: The rem edies of purchaser set forth herein are exclusive, and the total liability of
OMEGA w it h re s p e c t t o t h is o rd e r, w h e t h e r b a s e d o n c o n t ra c t , w a rra n t y, n e g lig e n c e ,
in d e m n ific a t io n , s t ric t lia b ilit y o r o t h e rw is e , s h a ll n o t e xc e e d t h e p u rc h a s e p ric e o f t h e
c o m p o n e n t u p o n w h ic h lia b ilit y is b a s e d . In n o e v e n t s h a ll O M EG A b e lia b le f o r
consequential, incidental or special dam ages.
CONDITIONS: Equipm ent sold by OMEGA is not intended to be used, nor shall it be used: (1) as a “Basic
Com ponent” under 10 CFR 21 (NRC), used in or with any nuclear installation or activity; or (2) in m edical
applications or used on hum ans. Should any Product(s) be used in or with any nuclear installation or
activity, m edical application, used on hum ans, or m isused in any way, OMEGA assum es no responsibility
as set forth in our basic WARRANTY/DISCLAIMER language, and, additionally, purchaser will indem nify
OMEGA and hold OMEGA harm less from any liability or dam age whatsoever arising out of the use of the
Product(s) in such a m anner.
RETURN REQUES TS / INQUIRIES
Direct all warranty and repair requests/inquiries to the OMEGA Custom er Service Departm ent. BEFORE
RETURNING ANY PRODUCT(S) TO OMEGA, PURCHASER MUST OBTAIN AN AUTHORIZED RETURN
(AR) NUMBER FROM OMEGA’S CUS TOMER S ERVICE DEPARTMENT (IN ORDER TO AVOID
PROCESSING DELAYS). The assigned AR num ber should then be m arked on the outside of the return
package and on any correspondence.
The purchaser is responsible for shipping charges, freight, insurance and proper packaging to prevent
breakage in transit.
FOR WARRANTY RETURNS, please have the
following inform ation available BEFORE
contacting OMEGA:
FOR NON-WARRANTY REPAIRS, consult OMEGA
for current repair charges. Have the following
inform ation available BEFORE contacting OMEGA:
1. Purchase Order number under which the product
was PURCHASED,
1. Purchase Order num ber to cover the COST
of the repair,
2. Model and serial num ber of the product under
warranty, and
3. Repair instructions and/or specific problem s
relative to the product.
2. Model and serial num ber of the product, and
3. Repair instructions and/or specific problem s
relative to the product.
OMEGA’s policy is to m ake running changes, not m odel changes, whenever an im provem ent is possible. This affords
our custom ers the latest in technology and engineering.
OMEGA is a registered tradem ark of OMEGA ENGINEERING, INC.
© Copyright 1999 OMEGA ENGINEERING, INC. All rights reserved. This docum ent m ay not be copied, photocopied,
reproduced, translated, or reduced to any electronic m edium or m achine-readable form , in whole or in part, without the
prior written consent of OMEGA ENGINEERING, INC.
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PSW-141 Series
M-3488 / 0011
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