Omega EWS-RH User Manual

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User’s Guide

EWS-RH

Relative Humidity/Temperature

Transmitter

MADE IN

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®

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®

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®

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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: [e-mail]

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:

R

max = (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

1

6

44%

+

+

–

–

5432

EWS-RH TEMPERATURE OUTPUT

PROCESS PANEL METER

POWER SUPPLY

1

6

72° F

+

+

–

–

5432

EWS-RH RELATIVE HUMIDITY OUTPUT

PROCESS PANEL METER

POWER SUPPLY

1

6

44%

+

+

–

–

5432

EWS-RH TEMPERATURE OUTPUT

PROCESS PANEL METER

POWER SUPPLY

1

6

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 re­calibrated 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

1

6

+

+

–

–

5432

16.80 mA

P1

P2

EWS-RH

Relative Humidity/Temperature Transmitter

7

Temperature Calibration Procedure

Recommended equipment:

Series 860 Thermistor Meter OMEGA®Model No. 865F or 865C

Series 400 Thermistor Probe, OMEGA®Model No.: ON-406-PP

Handheld Digital Multimeter, OMEGA®Model No.: HHM29

1. Remove enclosure cover.

2. Connect transmitter as shown in figure below.

3. Apply power to transmitter and allow to warm up for 10 min.

4. Place unit on workbench with temperature reference probe next to unit.

5. Allow output from transmitter and reference probe to stabilize.

6. Observe the reading on the handheld thermometer coming from the
reference probe.

7. Without touching the unit with your hand, adjust potentiometer “P4” for
a current output of the transmitter that matches the temperature
measured by the reference probe. Note: if you hold the unit with your
hand, the unit will sense heat from your hand and cause a bad
calibration.

Use this formula:

(

Ambient - 5

x 16

)

+4

135

Example:

If your reference probe measures 70°F (21.11°C) you need to adjust the
transmitter’s current output to be 11.70 mA.

8. Calibration complete.

Figure 5: Temperature Calibration Procedure

MULTIMETER

POWER SUPPLY

1

6

+

+

–

–

5432

11.70 mA

P4

EWS-RH
Relative Humidity/Temperature Transmitter

8

Relative Humidity Specifications

Range: 5-95% (non-condensing)

Accuracy @ 25°C: From 5-20%, ± 4% RH

From 20-80%, ± 3% RH
From 80-95%, ± 4% RH

Repeatability: ± 1% RH

Temp. Compensation Range: 5 to 140°F (-15 to 60°C)

Output: 4-20 mA or 1-5 Vdc (scaled for 0 to

100% RH)

Power: 8-24 Vdc @ 20mA

Max Loop Resistance: Ohms = (V supply - 8V)/.02 A

RH Time Constant: 100 sec., from 20-90%, 60 sec from

90-20%

Sensor Type: Thin Film Polymer Capacitor

Temperature Specifications

Range: 5 to 140°F (-15 to 60°C)

Accuracy @ 25°C

In Still Air: ± 1.2°F (0.7°C) @ 25°C

± 2.5°F (1.4°C) across full range

In Moving Air: ± 2.5°F (1.4°C) @ 25°C

± 3°F (1.7°C) across full range

Note: Not recommended for fast moving air applications.

Repeatability: ± 0.5°F (0.3°C)

Output : 4-20 mA or 1-5 Vdc (scaled across

range)

Temp. Time Constant: (for 63.2% response)

9 sec. in moving air (1 M/sec.),
30 sec. in still air

Power: 8-24 Vdc @ 20 mA

Max Loop Resistance: Ohms = (V supply - 8V)/.02 A

Sensor Type: Solid State

General Specifications

Enclosure Material: Acrylonitrile Butadiene

Dimensions: 79 x 54 x 45mm (3.12 L x 2.12 W x

1.78" H)

Weight: 54 g(.12 lb)

9

NOTES:

EWS-RH

Relative Humidity/Temperature Transmitter

10

NOTES:

EWS-RH
Relative Humidity/Temperature Transmitter

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
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, moisture or vibra­tion; improper specification; misapplication; 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. However,
OMEGA neither assumes responsibility for any omissions or errors nor assumes liability
for any damages that result from the use of its products in accordance with information
provided by OMEGA, either verbal or written. OMEGA warrants only that the parts
manufactured by it will be as specified and free of defects. OMEGA MAKES NO OTHER
WARRANTIES OR REPRESENTATIONS OF ANY KIND WHATSOEVER, EXPRESS OR
IMPLIED, EXCEPT THAT OF TITLE, AND ALL IMPLIED WARRANTIES INCLUDING ANY
WARRANTY OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
HEREBY DISCLAIMED. LIMITATION OF LIABILITY: The remedies of purchaser set forth
herein are exclusive, and the total liability of OMEGA with respect to this order, whether
based on contract, warranty, negligence, indemnification, strict liability or otherwise, shall
not exceed the purchase price of the component upon which liability is based. In no event
shall OMEGA be liable for consequential, incidental or special damages.

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 applications 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 RETURNING 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,

2. Model and serial number of the product

under warranty, and

3. Repair instructions and/or specific

problems relative to the product.

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, and

3. Repair instructions and/or specific problems

relative to the product.

OMEGA’s policy is to make running changes, not model changes, whenever an improvement is possible.
This affords our customers the latest in technology and engineering.

OMEGA is a registered trademark of OMEGA ENGINEERING, INC.
© Copyright 2003 OMEGA ENGINEERING, INC. All rights reserved. This document may not be copied, photocopied,

reproduced, translated, or reduced to any electronic medium or machine-readable form, in whole or in part, without
the prior written consent of OMEGA ENGINEERING, INC.

M3501/1001

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