Omega HX71 Series User manual

HX71 SERIES
RH Probe/Transmitter
HX71-NB
MODEL
HX71 MODEL
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User’s Guide
RoHS 2 Compliant

Servicing North America:
U.S.A.: Omega Engineering, Inc., One Omega Drive, P.O. Box 4047
Stamford, CT 06907-0047 USA
Toll-Free: 1-800-826-6342 (USA & Canada only)
Customer Service: 1-800-622-2378 (USA & Canada only)
Engineering Service: 1-800-872-9436 (USA & Canada only)
Tel: [phone] Fax: [phone]
e-mail: [email protected]
For Other Locations Visit omega.com/worldwide
omega.com [email protected]
The information contained in this document is believed to be correct, but OMEGA accepts no liability for any errors it contains,
and reserves the right to alter specifications without notice.

TABLE OF
CONTENTS
HX71 SERIES
RH Probe/Transmitter
i
Section Page
1. General Description .................................................................. 1
2. Unpacking ................................................................................... 1
3. Theory of Operation .................................................................. 2
4. Installation and Mounting ................................................... 3-4
5. Electrical Connections .............................................................. 5
6. Wiring Examples ........................................................................ 6
7. Relative Humidity Output Calculations ................................ 6
8. RH Measured Vs Output Reading Table .............................. 7
9. Calibration and Maintenance .................................................. 8
10. Specifications .............................................................................. 9

FIGURES HX71 SERIES
RH Probe/Transmitter
ii
Figure Page
Figure 1 Basic Transmitter Set-up
With Current Loop Output ............................................ 2
Figure 2 HX71 Dimensions ............................................................ 3
Figure 3 HX71 Mounting ................................................................ 3
Figure 4 HX71-NB Dimensions and Mounting .......................... 4
Figure 5 Current Transmitter Wiring Example
(4-20 mA) ........................................................................... 6
Figure 6 Voltage Transmitter Wiring Example
(0-1 Vdc and 0-5 Vdc) ...................................................... 6

1
General Description
1
1. General Description
The OMEGA®HX71 Series Relative Humidity Transmitter’s provide
a linearized and temperature compensated output signal of 4 to 20
mA, 0 to 1 Vdc or 0 to 5 Vdc depending upon the model selected. The
output signal has been calibrated and scaled 0 to 100% for Relative
Humidity. A thin film polymer capacitor senses relative humidity and is
protected by a stainless steel cap that is easily removed for cleaning. The
Nema-4 stainless steel enclosure and cable entry connection provides
weathertight protection.
2. 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:
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.
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 HX71 transmitter.
• This Manual, # M-4543 (1 ea.)
• Dewpoint Card (1 ea.)
Recommended Power Supply
For HX71-MA and HX71-MA-NB, Omega Model PST-10
For HX71-V1, HX71-V2, HX71-V1-NB and HX71-V2-NB: Omega
Model FPW-15
Complimentary Instruments
iSeries®Panel Meters and Controllers
Recommended Accessories
Duct/Wall Mounting Kit, OMEGA®Part No.: IND-KIT (For HX71-
MA, HX71-V1, HX71-V2)
Transmitter Cable, OMEGA®Part No.: TX4-100 (100 ft)
RH Calibration Kit, OMEGA®Part No.: HX92-CAL
NOTE

2
3. 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 HX71
Series the amount of current allowed to flow in the loop will vary
depending on the relative humidity or temperature being measured
by the sensor(s). 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 HX71 to function properly is found by using the
following formula:
Rmax = (power supply voltage – 8 volts) ÷ 0.02 amps
EXAMPLE: (When using a 10 Vdc power supply).
Rmax = (10 – 8) ÷ 0.02 amps = 800 ohms max loop
resistance
Figure 1 - Basic Transmitter Set-up With Current Loop Output
3Theory of Operation
HX71 CABLE
HX71 CABLE
RED WIRE
RED WIRE
SHIELD WIRE
SHIELD WIRE
BLACK WIRE
BLACK WIRE
PANEL METER
PANEL METER
POWER SUPPLY
POWER SUPPLY
+ 10V
24V
–
50%
50%
+ –
+ –
+ –
WHITE WIRE

3
4. Installation and Mounting
Your HX71 Series RH Probe/Transmitter needs to be installed in
applications that allow for well circulated air flow to meet the published
specifications outlined here in this manual in Section 10.
OMEGA’s HX71 transmitter’s are designed for either wall or duct
mounting. A wall/duct mounting kit is available, OMEGA®Part
No.:HX90DM-KIT.
Figure 1-3. - RH-USB Dimensions
Figure 3 - HX71 Mounting
131 (5.18)
Ø 16 (5/16)
DIMENSIONS: mm (in)
4
Installation and Mounting
HX71
MOUNTING BUSHING
MOUNTING SCREW
DUCT WALL
MOUNTING GASKET
MOUNTING PLATE
MOUNTING
NUT
MOUNTING
SCREW
HX71
CLAMP
NOTE

4
Figure 4 - HX71-NB Dimensions and Mounting
4Installation and Mounting
52.6 (2.07)
65 (2.56)
50 (1.97)
45.3 (1.78)
19.5
(0.76)
38 (1.50)
MOUNTING
HOLE
4.3 (0.17) DIA.
MOUNTING HOLE
4.3 (0.17) DIA.
16 (0.62) DIA.
DIMENSIONS: mm (in)

5
5. Electrical Connections
All electrical connections and wiring should be performed by a suitably
trained professional only.
Model: HX71-MA, HX71-MA-NB
(2-Wire Current Output)
Red Wire: + Power Supply
Black Wire: 4-20 mA Output
Bare Wire: Shield, Earth Ground
Model: HX71-V1, HX71-V2, HX71-V1-NB, HX71-V2-NB
(3-Wire Voltage Output)
Red Wire: + Power Supply
Black Wire: - Power/-Output
Wire: + Output
White Bare Wire: Shield, Earth Ground
Your HX71 Series RH Probe/Transmitter has not been designed for, nor
is it recommended for, use in medical or nuclear applications.
Your HX71 Series RH Probe/Transmitter should never be installed in or
anywhere near explosive or flammable materials.
CAUTION
CAUTION
5
Electrical Connections

6
6. Wiring Examples
Current output model HX71-MA, HX71-MA-NB (4 to 20 mA)
Figure 5 - Current Transmitter Wiring Example
Voltage output models HX71-V1, HX71-V2, HX71-V1-NB, HX71-V2-
NB (0 to 1 Vdc or 0 to 5 Vdc)
Figure 6 - Voltage Transmitter Wiring Example
7. Relative Humidity Output Calculations
To calculate % Relative Humidity by measuring the current or voltage
output use the following formulas.
For 4-20 mA output:
% RH = (Current measured in milliamps – 4) ÷ 0.16
EXAMPLE: (11.04 mA – 4) ÷ 0.16 = 44% RH
For 0 to 1 Vdc output:
% RH = (Voltage measured in volts x 100)
EXAMPLE: 0.44 Vdc x 100 = 44% RH
HX71 CABLE
HX71 CABLE
RED WIRE
RED WIRE
SHIELD WIRE
SHIELD WIRE
BLACK WIRE
BLACK WIRE
PANEL METER
PANEL METER
POWER SUPPLY
POWER SUPPLY
+ 10V
24V
–
50%
50%
+ –
+ –
+ –
WHITE WIRE
HX71 CABLE
HX71 CABLE
RED WIRE
RED WIRE
SHIELD WIRE
SHIELD WIRE
BLACK WIRE
BLACK WIRE
PANEL METER
PANEL METER
POWER SUPPLY
POWER SUPPLY
+ 10V
24V
–
50%
50%
+ –
+ –
+ –
WHITE WIRE
6
HX71 SERIES
RH Probe/Transmitter