User’s Guide
www.omega.com
e-mail: info@omega.com
PSW 3 1 SERIES
ELECTRONIC PRESSURE SWITCH FOR PNEUMATIC APPLICATIONS
ELECTRONIC PRESSURE SWITCH FOR PNEUMATIC APPLICATIONS
PSW31 Series
APPLICATION
Ideal for Control of Filtered Compressed Air,
Lubricated or Non-Lubricated
FEATURES
Real-Time LED Status Display of Pressure
Adjustable Hysteresis
Off-Line Calibration
Fast, Accurate Response
Extensive Service Life
SPECIFICATIONS
Ports/ Mounting Plate
Adjustment Range
Maximum Pressure
Temperature Rating
Ambient
1/ 4" NPT
-14 to 350 PSI (-1 to 25 bar)
See Part Number Identification Table
.43
(11)
14° to 140° F (-10° to 60° C)
14° to 175° F (-10° to 80° C)
Media
Temperature Sensitivity
@ Zero Point
Set Point Shifts 0.4% of FS/ 10°C
1.85 (47)
1.18 (30)
@ Set Point Pressure Set Point Shifts 0.3% of FS/ 10°C
Electronics
Pressure Sensor, Microprocessor
Evaluation Circuitry and
Solid-state Output Driver
Switching/ Reset Point
Linearity
Electrical Connector
Adjustable between 0 – 100% of FS
< 0.5% of Final Value ± 1 digit
DIN Style Plug with Removable
Cable Plug Adapter
Ø.31 (8)
MATERIALS OF CONSTRUCTION
Housing
Die-Cast Zinc
.05 (1.2)
.79 (20)
1.18 (30)
All dimensions in inches (mm)
ELECTRONIC PRESSURE SWITCH FOR PNEUMATIC APPLICATIONS
ELECTRICAL PARAMETERS
Electrical connection
DIN 43650 Table A
18 to 32V DC
10% (within 18 to 32V)
<50 mA (plus load current)
Power supply (polarity safe)
Permissible residual ripple
Current consumption
DIN 43650
1
+24V
3 Uout Imax = 1A
Micro-
Controller
E2PROM
(SP,RP)
p
=
Load
0V
PE
2
I
SP RP
SWITCHING OUTPUT
Switching mode
Open collector PNP switched to supply
(suited for inductive load)
Output voltage
Contact rating
Supply voltage minus 1.5V (approx)
I
= 1A (short-circuit proof)
max
Switching time
Service life
< 5ms
100 million switching cycles
Switching logic
Signal “on” with rising pressure, if SP* > RP**
Signal “on” with falling pressure, if SP < RP
* SP = Switching point
**RP = Reset point
PART NUMBER IDENTIFICATION
SWITCHING
STEP
PART
NUMBER
PRESSURE
RANGE – PSI
MAXIMUM
PRESSURE
SIZE OF
DISPLAY*
PSW31B
-14 – 15
0 – 145
0 – 350
145
440
580
0.14
0.6 – 0.7
1 – 2
PSW31C
PSW31D
*Pressure display in PSI
I N S T R U C T I O N
M A N U A L
supply is switched on. Release this button
Case 2
ADJUSTING THE SWITCHING POINTS (SP)
again after the power supply has been
switched on. The display will then show the
buffering time in milliseconds (e.g. 03) or
seconds. The cursor buttons M, M can be
used to set the buffering time to 03, 06,
12, 24 or 50 ms or 0.1, 0.2 or 0.4
seconds. When this has been done, press
SP to store the setting.
Positive hysteresis
1
AND RESET POINTS (RP)
Switching point
0
a) Adjusting the switching point.
p
Case 1
or Case 2
f) Window mode
Q
Q
If it is desired to monitor whether the pressure
lies within a certain range, a switching window
can be created for this purpose. The pressure
switch will then indicate cases in which the
actual pressure lies above or below this area.
In order to set a switching window, the two
buttons SP and M must be pressed
simultaneously before the power supply is
switched on.
d) Setting the pressure switch to ambient
pressure = 0.
Since ambient pressure varies according to
altitude, the user may re-calibrate the zero
point to match local conditions.
p
p
Press and hold the SP button. The display
will show the previous switching pressure
setting, and the dotted bar will flash while
the button is pressed down (case 1).
Press the button RP before the power
supply is switched on. Release this button
again after the power supply has been
switched on and the display test has run.
The display will then show "OFS". The
cursor buttons M, M can be used to set the
pressure display to 0. When this has been
done, press SP to store the setting.
Release these buttons again after the power
supply has been switched on and the display
test has run. The display will then show the
operating mode.
You can now use the cursor keys to adjust
the switching point upwards or downwards.
If a cursor key is held down, the values will
change faster. When the cursor key is
released again, the switch-on pressure
setting will cease to change. This setting is
stored and activated when the SP button is
released, after which the display will show
the current pressure value and the bar will
quit flashing.
The cursor buttons M,M can now be used to
change the operating mode until "FEn"
e) Hysteresis mode
(standing for "Window") in the display. When
this has been done, press SP to store the
setting. The button SP can be used to display
the switching-point setting, which can be
modified by means of the cursor buttons M, M.
If it is desired to operate with a fixed
hysteresis value instead of the reset point,
this value can be selected as desired.
In order to set a hysteresis value, the two
buttons SP and M must be pressed
simultaneously before the power supply
is switched on.
b) Adjusting the reset point.
The distance between the switching point and
reset point is the switching window. If the
switching point is lower than the reset point, a
signal will be output as long as the pressure
lies within the preset window (case 1, rising
pressure). If the switching point is higher than
the reset point, a signal will be output as long
as the pressure lies outside the preset window
(case 2, rising pressure). In the case of falling
pressure, the signal is inverted.
Case 3
or Case 4
Release these buttons again after the
power supply has been switched on and the
display test has run. The display will then
show the operating mode. The cursor
buttons M,M can now be used to change
the operating mode until "HYS" appears in
the display. When this has been done,
press SP to store the setting.
Q
Q
p
p
Press and hold the RP button. The display
will show the previous reset pressure
setting, and the dotted bar will flash while
the button is pressed down.
Case 1
The SP button can be used to display the
switching-point setting, which can be
modified by means of the cursor buttons
M,M.
On = Pressure within window
1
You can now use the cursor keys to adjust
the reset point in the same manner as
described above.
The button RP can be used to display the
hysteresis setting, which can also be
modified by means of the cursor buttons
M,M.
During both adjustment operations, it may
occur that the hysteresis graph changes
from one state to another at the time a
transition is made through the point
"Switching pressure = Reset pressure".
When both points are correctly set, the
hysteresis graph will also be correct. You
can change between SP and RP as often as
you wish until the settings are correct.
0
p
SP
<
RP
Case 2
Negative hysteresis means: Signal “on”
with rising pressure (case 1).
Off = Pressure within window
1
Positive hysteresis means: Signal “on” with
falling pressure (case 2).
If the switching point is modified, this will
automatically also result in a change in the
reset point by a value equal to the
hysteresis setting.
c) Setting a buffering time.
In order to prevent brief pressure “spikes”
or “surges” from causing undesired
0
p
RP
<
SP
Case 1
switching, a buffering time can be entered.
The effect of this is that pressure changes
are evaluated only if the pressure signal in
question is present for longer than the
buffering time. In order to set a buffering
time, press the button SP before the power
Std
=
Standard mode, switching and reset
points adjustable
Negative hysteresis
1
HYS = Hysteresis mode, switching point and
hysteresis adjustable
FEn
=
Window mode, switching window
adjustable
Switching point
0
p
Switching Characteristic Graphs
Signal “off” with falling pressure
Signal “off” with rising pressure
Signal “on” with rising pressure
Signal “on” with falling pressure
Setting RP < SP
Setting RP > SP
Setting SP* > RP**
Setting SP < RP
p
p
RP
p
p
SP
SP
RP
RP
SP
RP
SP
t
t
t
t
UA
UA
U
U
* SP = Switching point
t
t
t
**RP = Reset point
t
Explanation:
When the switching point (SP) is adjusted HIGHER than the reset point (RP), then the switching output will be “normally off”.
When the switching point (SP) is adjusted LOWER than the reset point (RP), then the switching output will be “normally on”.
Position of operating elements
E R R O R M E S
Display of hardware errors or malfunctions
Display Meaning Cause / Remedy
S
A G E S
O.Er
Output error
Error at switching output: Circuit-breaker defective, feedback loop
to processor open circuit. Repair necessary.
Pressure display
2
2
E.Er
I.Er
E PROM error
E PROM module defective or connection to processor faulty.
Repair necessary.
Switching
function graph
Initialization error Checksum of initialization data incorrect. Remedy: Call up any
SETUP function and acknowledge the setting with SP.
Switching output LED
This error message is caused by a data error. All setup values
should therefore be checked and corrected if necessary.
Switching point button
Reset point button
Raise switching
or reset point button
C.Er
Calibration error
Short-circuit low
Checksum of calibration data incorrect. Recalibration necessary.
SC.L
Short-circuit between output and ground. Check wiring:
Power supply may be too weak for connected load (leading
to collapse of voltage, particularly with loads with a high switch-on
current such as incandescent lamps or capacitances).
Lower switching
or reset point button
UFL
OFL
Underflow
Overflow
The applied pressure is below the measuring range:
Increase pressure until it is within the measuring range.
The applied pressure is above the measuring range:
Decrease pressure until it is within the measuring range.
Display of hardware errors or malfunctions (can be switched off)
Display Meaning Cause / Remedy
SC.H
Short-circuit high Short-circuit between output and power supply. Check wiring.
If the switching line from the load (e.g. electrical control
device, PLC or similar) is being held at an open-circuit
potential of > 3V, or if several pressure switches are being
operated in parallel, this function should be switched off.
Disconnection: M during display test, then adjust with M or M.
U.Lo
Voltage low
Power supply voltage too low (<17V).
Check power supply: Load may be too large.
Disconnection: M during display test, then adjust with M or M.
Messages generated by calling SETUP functions
Cod
CLC
txx
Meaning
Requested code or code programming
Deletion of current code
Clear code
Delay time
(Buffering time)
Setting of filter time constant
xx = Switching output delay
xx {03, 06, 12, 24, 50} in ms and
xx {O.1, 0.2, O.4} in s.
OFS
Offset
Request for offset adjustment using M and M buttons
Short-circuit monitoring activated
Voltage monitoring activated
SC.H
U. LO
OFF
Short-circuit high
Voltage low
Off
Short-circuit or voltage monitoring deactivated
Std
HYS
FEn
Standard mode
Hysteresis mode
Window mode
Standard mode activated
Hysteresis mode activated
Window mode activated
U-C
I-C
Voltage calibration
Current calibration
Voltage output selected
Current output selected
WARRANTY/DISCLAIMER
OMEGA ENGINEERING, INC. warrants this unit to be free of defects in materials and workmanship for a period
of 13 months from date of purchase. OMEGA’s Warranty adds an additional one (1) month grace period to the
normal one (1) year product warranty to cover handling and shipping time. This ensures that OMEGA’s customers
receive maximum coverage on each product.
If the unit malfunctions, it must be returned to the factory for evaluation. OMEGA’s Customer Service Department
will issue an Authorized Return (AR) number immediately upon phone or written request. Upon examination 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 limited to mishandling,
improper interfacing, operation outside of design limits, improper repair, or unauthorized modification. This WAR-
RANTY 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, moisture or vibration; improper specification; mis-
application; misuse or other operating conditions outside of OMEGA’s control. Components, which wear, are not
warranted, including but not limited to contact points, fuses, and triacs.
OMEGA is pleased to offer suggestions on the use of its various products. How ever, 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 as specified and free of
defects. OMEGA MAKES NO OTHER WARRANTIES OR REPRESENTATIONS OF ANY KIND WHATSO-
EVER, EXPRESS OR IMPLIED, EXCEPT THAT OF TITLE, AND ALL IMPLIED WARRANTIES INCLUDING
ANY WARRANTY OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE HERE-
BY DISCLAIMED. LIMITATION OF LIABILITY: The rem edies of purchaser set forth herein are exclusive,
and the total liability of OMEGA w ith respect to this order, w hether based on contract, w arranty, neg-
ligence, indem nification, strict liability or otherw ise, shall not exceed the purchase price of the
com ponent upon w hich liability is based. In no event shall OMEGA be liable for consequential, inci-
dental or special dam ages.
CONDITIONS: Equipment sold by OMEGA is not intended to be used, nor shall it be used: (1) as a “Basic
Component” under 10 CFR 21 (NRC), used in or with any nuclear installation or activity; or (2) in medical appli-
cations or used on humans. Should any Product(s) be used in or with any nuclear installation or activity, medical
application, used on humans, or misused in any way, OMEGA assumes no responsibility as set forth in our basic
WARRANTY / DISCLAIMER language, and, additionally, purchaser will indemnify OMEGA and hold OMEGA
harmless from any liability or damage whatsoever arising out of the use of the Product(s) in such a manner.
RETURN REQUESTS / INQUIRIES
Direct all warranty and repair requests/inquiries to the OMEGA Customer Service Department. BEFORE RETURN-
ING ANY PRODUCT(S) TO OMEGA, PURCHASER MUST OBTAIN AN AUTHORIZED RETURN (AR) NUMBER
FROM OMEGA’S CUSTOMER SERVICE DEPARTMENT (IN ORDER TO AVOID PROCESSING DELAYS). The
assigned AR number should then be marked 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 information available
BEFORE contacting OMEGA:
1. Purchase Order number under which the
product was PURCHASED,
FOR NON-WARRANTY REPAIRS, consult
OMEGA for current repair charges. Have the following
information available BEFORE contacting OMEGA.
1. Purchase Order number to cover the COST
of the repair,
2. Model and serial number of the product
under warranty, and
3. Repair instructions and/or specific problems
relative to the product.
2. Model and serial number of the product, and
3. Repair instructions and/or specific problems 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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