Omega EWS-RH User manual

www.omega.com
e-mail: [email protected]
User’s Guide
EWS-RH
Relative Humidity/Temperature
Transmitter
MADE IN
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It is the policy of OMEGA to comply with all worldwide safety and EMC/EMI regulations that
apply. OMEGA is constantly pursuing certification of its products to the European New Approach
Directives. OMEGA will add the CE mark to every appropriate device upon certification.
The information contained in this document is believed to be correct, but OMEGA Engineering, Inc. accepts
no liability for any errors it contains, and reserves the right to alter specifications without notice.
WARNING: These products are not designed for use in, and should not be used for, human applications.

TABLE OF
CONTENTS
EWS-RH
Relative Humidity/Temperature Transmitter
i
Page
General Description .................................................................... 1
Unpacking .................................................................................... 1
Theory of Operation ................................................................... 1
Mounting ..................................................................................... 3
RH/Temperature Calculations ................................................. 5
Calibration ....................................................................................6
Relative Humidity Calibration Procedure ...............................6
Temperature Calibration Procedure ........................................ 7
Specifications ............................................................................... 8

FIGURES EWS-RH
Relative Humidity/Temperature Transmitter
ii
Figure Page
Figure 1 Mounting Diagram............................................................ 3
Figure 2 Transmitter Wiring Examples For Current Output...... 4
Figure 3 Transmitter Wiring Examples For Voltage Output ..... 4
Figure 4 Relative Humidity Calibration Procedure ..................... 6
Figure 5 Temperature Calibration Procedure ............................... 7

EWS-RH
Relative Humidity/Temperature Transmitter
1
General Description
The OMEGA®Model EWS-RH is a combination dual output, relative
humidity/temperature transmitter. A thin film temperature
compensated, polymer capacitor senses relative humidity while a solid
state temperature sensor measures ambient temperature. Independent
user selectable 4-20 mA or 1-5 Vdc outputs are provided for both
measured parameters via a terminal strip connection.
Unpacking
Remove the packing list and verify that you have received all your
equipment. If you have any questions about the shipment, please call
our Customer Service Department at
1-800-622-2378 or 203-359-1660. On the web you can find us at:
www.omega.com e-mail: [email protected]
When you receive the shipment, inspect the container and equipment
for any signs of damage. Note any evidence of rough handling in
transit. Immediately report any damage to the shipping agent.
NOTE: The carrier will not honor any damage claims unless
all shipping material is saved for inspection. After
examining and removing contents, save packing material
and carton in the event reshipment is necessary.
The following items are supplied in the box with your transmitter.
This Manual, # M-3501 (1 ea.)
Dewpoint Card (1 ea.)
#6 Wall Anchor (2 ea.)
#6 Mounting Screw (2 ea.)
NOTE

EWS-RH
Relative Humidity/Temperature Transmitter
2
Additional EWS Series Models Available
Model Description
EWS-TC-(*) Wall mount thermocouple sensor
(* = insert type,J, K, T, E)
EWS-RTD Wall mount RTD sensor (100 Pt., .00385)
EWS-TX Wall mount solid state temperature transmitter
EWS-BP-A Wall mount barometric pressure transmitter
Theory of Operation
A 4-20 mA loop is a series loop in which a transmitter will vary the
current flow depending on the input to the transmitter. In the EWS-RH
the amount of current allowed to flow in the loop will vary depending
on the relative humidity or temperature being measured by the sensor.
Some advantages of a current output over a voltage output is that the
signal measured is less susceptible to electrical noise interference and
the loop can support more than one measuring instrument as long as
the maximum loop resistance is not exceeded.
A typical application utilizing a current loop will normally consist of a
power supply, the transmitter and a meter, recorder or controller to
measure the current flow. The loop resistance in the sum of the
measuring instruments and wire used. The maximum allowable loop
resistance for the EWS-RH to function properly is found by using the
following formula:
Rmax = (power supply voltage - 8 volts)/.02 amps
For applications that require a voltage output signal the EWS-RH has a
built-in 250 Ohm shunt resistor that will convert the transmitters
output to a 1-5 Vdc signal when wired correctly. See "Transmitter Wiring
Examples" in this manual.
Recommended Accessories
Power Supply, OMEGA®Part No.: PSU-93
Shielded 4-conductor cable, OMEGA®Part No.: TX4-100
Conduit Box Mounting Kit, OMEGA®Part No.: EWS-MB

EWS-RH
Relative Humidity/Temperature Transmitter
3
Note: These units are not designed, nor recommended for
medical, Explosive Environment or outdoor applications.
Mounting
OMEGA's EWS Series of sensors and transmitters are designed for wall
mounting in locations that are free from dirt, grease, food particles and
condensing moisture such as manufacturing clean rooms, computer
rooms and laboratory type environments. Plastic wall anchors and
mounting screws are included for mounting to standard wallboard. A
conduit box mounting bracket/wall plate adapter kit is also available
as an option that will allow the transmitter to be mounted to a standard
electrical conduit box.
Order OMEGA®Model No.: EWS-MB.
Figure 1: Mounting Diagram
NOTE
COVER PLATE
GROMET
ADAPTER PLATE
CONDUIT BOX (NOT INCLUDED) IS SHOWN FOR
REFERENCE ONLY
®

EWS-RH
Relative Humidity/Temperature Transmitter
4
Figure 2: Transmitter Wiring Examples
For Current Output (4-20 mA)
Figure 3: Transmitter Wiring Examples
For Voltage Output (1-5 Vdc)
EWS-RH RELATIVE HUMIDITY OUTPUT
PROCESS PANEL METER
POWER SUPPLY
16
44%
+
+
–
–
5432
EWS-RH TEMPERATURE OUTPUT
PROCESS PANEL METER
POWER SUPPLY
16
72°F
+
+
–
–
5432
EWS-RH RELATIVE HUMIDITY OUTPUT
PROCESS PANEL METER
POWER SUPPLY
16
44%
+
+
–
–
5432
EWS-RH TEMPERATURE OUTPUT
PROCESS PANEL METER
POWER SUPPLY
16
72°F
+
+
–
–
5432

EWS-RH
Relative Humidity/Temperature Transmitter
5
RH/Temperature Calculations
To calculate % Relative Humidity by measuring current output in
milliamperes.
(Current output - 4 )= % RH
.16
To calculate Temperature by measuring current output in milliamperes.
(Current output - 4 x 135 ) +5 = Temp (°F)
16
RH Measured Vs Output Reading Temperature Measured Vs
Output Reading
% Relative Output
Humidity Current(mA) Voltage(Vdc)
5 4.8 1.2
10 5.6 1.4
15 6.4 1.6
20 7.2 1.8
25 8 2
30 8.8 2.2
35 9.6 2.4
40 10.4 2.6
45 11.2 2.8
50 12 3
55 12.8 3.2
60 13.6 3.4
65 14.4 3.6
70 15.2 3.8
75 16 4
80 16.8 4.2
85 17.6 4.4
90 18.4 4.6
95 19.2 4.8
Temperature Output
°C (°F) Current(mA) Voltage(Vdc)
-15 (5) 4 1
-10 (14) 5.07 1.27
0 (32) 7.20 1.80
10 (50) 9.33 2.33
20 (72) 11.94 2.99
30 (86) 13.60 3.40
40 (104) 15.73 3.93
50 (122) 17.87 4.47
60 (140) 20 5

Calibration
Your transmitter has been factory calibrated to meet or exceed the
specifications outlined in this manual. To maintain original
specifications it is generally recommended that your transmitter be re-
calibrated on an annual basis depending on operating conditions.
Relative Humidity Calibration Procedure
Recommended equipment:
Humidity Generator/Calibrator Kit, OMEGA®Model No.: RHCL-KIT
Handheld Digital Multimeter, OMEGA®Model No.: HHM29
Note: Do not make adjustments to potentiometer “P3”, this
is a factory setting and is not field adjustable. If “P3” is
disturbed the transmitter will need to be returned to the
factory for service.
1. Remove enclosure cover
2. Connect transmitter as shown in figure below.
3. Apply power to transmitter and allow to warm up for 15 min.
4. Place sensor in a 20% RH environment and allow to stabilize for 20 min.
5. Adjust potentiometer “P1” for a output reading of 7.2 mA
6. Place sensor in a 80% RH environment and allow to stabilize for 20 min.
7. Adjust potentiometer "P2" for an output reading of 16.8 mA
8. Repeat steps 4, 5, 6, 7 as necessary until proper readings are maintained.
9. Calibration complete.
Figure 4: Relative Humidity Calibration Procedure
NOTE
EWS-RH
Relative Humidity/Temperature Transmitter
6
MULTIMETER
POWER SUPPLY
16
+
+
–
–
5432
16.80 mA
P1
P2