Rotronic HygroFlex 1, HygroFlex 2, HygroFlex 3 Instruction Manual

HygroFlex

Humidity Temperature Transmitter

Instruction Manual

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Contents

Overview........................................................................................................................................3

General Description........................................................................................................................4

Power Requirements..................................................................................................................4

Probes and Probe Inputs ............................................................................................................5

Analog Outputs (HygroFlex 1 and HygroFlex 3).........................................................................7

RS232 Digital Port......................................................................................................................8

HW3 Software ............................................................................................................................8

RS485 Networking (HygroFlex 2 and HygroFlex 3).....................................................................8

Unit System................................................................................................................................9

Optional Display and Keypad ......................................................................................................9

Keypad.......................................................................................................................................9

Installation....................................................................................................................................10

Mechanical Installation .............................................................................................................10

Electrical Installation.................................................................................................................12

Network Configuration and Wiring (HygroFlex 2 and HygroFlex 3)............................................16

Configuration of the Analog Outputs ......................................................................................... 17

Functions .....................................................................................................................................17

CALCULATE (HygroFlex 2 and HygroFlex 3)............................................................................ 18

DISPLAY (HygroFlex 2 and HygroFlex 3) .................................................................................19

ADJUST M.PT (2- to 4-point adjustment against a reference environment) ...............................19

ADJUST 1PT (1-point adjustment against a reference environment)......................................... 21

ADJUST REF (1-point adjustment against a reference probe) ...................................................22

PROBE .................................................................................................................................... 22

RS STATUS.............................................................................................................................23

SYS STATUS...........................................................................................................................23

Calibration with a HygroPalm Indicator ......................................................................................... 24

Display the Transmitter Measurements.....................................................................................25

Functions (except ADJUST M.PT and ADJUST 1PT)................................................................ 25

Functions ADJUST M.PT and ADJUST 1PT.............................................................................25

Function ADJUST REF.............................................................................................................25

Environmental Limits....................................................................................................................26

Maintenance.................................................................................................................................26

On-Site Maintenance................................................................................................................26

Factory / Metrology Lab. Maintenance ......................................................................................26

Specifications...............................................................................................................................27

Appendix 1: Practical Advice for Measuring Humidity.................................................................... 29

Appendix 2: Resolution of the Analog Signals...............................................................................29

Appendix 3: Maintenance of the ROTRONIC probes.....................................................................30

Cleaning or Replacing the Dust Filter of the Probe....................................................................30

Periodic Calibration Check of the Probes.................................................................................. 30

Appendix 4: Calibration Basics ..................................................................................................... 31

Temperature Calibration........................................................................................................... 31

Humidity Calibration..................................................................................................................31

Appendix 5: Humidity Definitions ..................................................................................................33

Appendix 6: Dew Point Accuracy..................................................................................................35

Appendix 7: RS232 Communication Protocol................................................................................ 36

Note: functions such as instrument configuration with a PC as well as the calibration of
HygroClip probes with a PC require the optional HW3 software. Instructions for using the
HW3 software are not included in this manual. These instructions are shipped separately on
the same CD ROM as the HW3 software.

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Overview

The HygroFlex is a series of 3-wire humidity temperature transmitters that is available with a wide
variety of probes for use in many different industrial and scientific applications. The HygroFlex
series uses a micro-processor based design to achieve unparalleled accuracy, reliability and
versatility.

The HygroFlex is available in 3 different models:

HygroFlex 1: basic industrial transmitter with analog outputs

relative humidity and temperature

- compatible with any ROTRONIC HygroClip digital probe

1)

- relative humidity and temperature analog outputs

- test connector for communication with the HygroPalm indicator

2)

- software-based calibration (HygroClip probes only)

- internal service connector (RS232) for configuration with PC (units, ranges)

- two linearized analog outputs, signal type (mA, V) configurable by means of jumpers

3)

- optional LC display and keypad

4)

1) ROTRONIC analog probes are also accepted with some restrictions

2) allows the HygroPalm to read the transmitter or to calibrate a digital probe

3) 0..1V, 0..5V, 0..10V, 0..20 mA, 4..20 mA

4) allows direct calibration of digital probes by the transmitter and direct access to other functions

HygroFlex 2: fully digital, networkable industrial transmitter

relative humidity, dew point (or other) and temperature

- compatible with any ROTRONIC HygroClip digital probe

1)

- optional analog input for second probe

2)

- relative humidity, temperature, dew point, wet bulb, mixing ratio, enthalpy, etc

3)

- test connector for communication with the HygroPalm indicator

4)

- software-based calibration (HygroClip probes only)

- RS232 and RS485 digital ports

5)

- optional LC display and keypad

6)

1) ROTRONIC analog probes are also accepted with some restrictions

2) pressure probe or ROTRONIC HygroClip digital probe – some restrictions apply

3) uses either a fixed barometric pressure value or the measurements from an analog pressure probe
for those parameters that require pressure as a computational input. The fixed pressure value can be
changed with the optional HW3 software.

4) allows the HygroPalm to read the transmitter or to calibrate a digital probe

5) The computed parameter (dew point or other) is not sent to these ports. Use of the HW3 software on
a PC allows real time computation of the dew point (or other) and facilitates both networking and
instrument configuration

6) allows direct calibration of digital probes by the transmitter and direct access to other functions

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HygroFlex 3: analog / digital, networkable industrial transmitter

relative humidity, dew point (or other) and temperature

- compatible with any ROTRONIC HygroClip digital probe

1)

- optional input for second probe

2)

- relative humidity, temperature, dew point, wet bulb, mixing ratio, enthalpy, etc

3)

- test connector for communication with the HygroPalm indicator

4)

- software-based calibration (HygroClip probes only)

- RS232 and RS485 digital ports

5)

- three linearized analog outputs, signal type (mA, V) configurable by means of jumpers

6)

- optional LC display and keypad

7)

1) ROTRONIC analog probes are also accepted with some restrictions

2) pressure probe or ROTRONIC HygroClip digital probe – some restrictions apply

3) Uses either a fixed barometric pressure value or the measurements from an analog pressure probe
for those parameters that require pressure as a computational input. The fixed pressure value can be
changed with the optional HW3 software.

4) allows the HygroPalm to read the transmitter or to calibrate a digital probe

5) The computed parameter (dew point or other) is not sent to these ports. Use of the HW3 software on
a PC allows real time computation of the dew point (or other) and facilitates both networking and
instrument configuration

6) 0..1V, 0..5V, 0..10V, 0..20 mA, 4..20 mA - corresponding to relative humidity, temperature and
computed parameter (or relative humidity of second probe)

7) allows direct calibration of digital probes by the transmitter and direct access to other functions

General Description

Power Requirements

The HygroFlex is available with a choice of two basic internal power modules:

- standard power module for operation with 12 to 35 VDC (maximum 300 mA) or with 12 to 24 VAC.

- optional power module for operation with voltages within the range of 90 to 264 VAC (50/60 Hz).

HygroFlex 1 HygroFlex 2 HygroFlex 3

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Probes and Probe Inputs

Model HygroFlex 1 HygroFlex 2 HygroFlex 3

number of probe inputs 1 1 (standard) or 2 (optional)
probe types (see below) ROTRONIC Digital

ROTRONIC Analog

ROTRONIC Digital

ROTRONIC Analog

Third-Party Analog
number of digital input channels 1 1 (input 1) + 1 (input 2 - optional)
number of analog input channels 2 2 (input 1) + 1 (input 2 - optional)
analog input A/D resolution 10-bit 10-bit

Unless otherwise specified when ordering, all probe inputs are factory programmed to accept a HygroClip
digital probe. Prior to using any analog probe, the corresponding input should be re-programmed. This can be
done with the HW3 software after connecting the RS232 port to a PC (see separate HW3 manual). Probe
input 1: accepts either a ROTRONIC HygroClip digital probe or a ROTRONIC analog probe with adapter
cable. Probe input 2: accepts either a 1-channel third-party analog probe (for example a pressure probe) or a
second ROTRONIC HygroClip digital probe with adapter cable.

HygroClip Digital Probes

The HygroFlex is primarily designed for use with the ROTRONIC HygroClip digital humidity
temperature probes. These probes permit to take full advantage of all the features and functions of
the HygroFlex such as the software based calibration.

The ROTRONIC HygroClip digital probes are highly accurate and are calibrated entirely by means
of software (no adjustment potentiometers). Because calibration and other data are stored in the
probe non-volatile memory, the probes are fully interchangeable. When a probe requires calibration
or has to be repaired, it can be replaced with another probe in a few seconds. The ROTRONIC
HygroClip digital probes are available in different configurations so as to meet the requirements of
each application:

HygroClip IW
for surface mount (area monitoring)

max. 85°C (185°F) – wire mesh filter

observe temperature limits of transmitter

electronics

HygroClip IC-1 (100mm) / IC-3 (250mm)
for through-wall installation
max. 200°C (392°F) - wire mesh filter

HygroClip IM-1 (120mm) / IM-3 (270mm)
for through-wall installation in high humidity
applications
max. 200°C (392°F) - wire mesh filter

HygroClip IE-1 (G ½”) / IE-2 (NPT ½”)
for compressed air (max. 50 bar / 725 PSI)
max. 85°C (185°F) – sintered steel filter

to avoid errors, temperature should be the
same on both sides of the mounting wall

HygroClip IC-05
for measurement in tight spaces
max. 100°C (212°F)

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Analog Probes

Depending on the model and options, the HygroFlex transmitters can be used with one or two
analog probes. Both the scale and unit of the analog input signals can be defined with the HW3
software. For example, an analog pressure probe may used to provide the local value of barometric
pressure for the computation of parameters such as the wet bulb temperature, mixing ratio or
enthalpy.

HygroClip ID
for through-wall installation
max. 200°C (392°F) at sensors – wire mesh filter

available with up to 700mm (27.6”) probe length

Probe Extension Cable AC1616/xxx

with built-in signal booster

xxx = 002 to 200
from 2 to 200 m (about 6.5ft to 656ft)
max. temperature 85°C (185°F)

HygroClip ID-EX-xxx (intrinsically safe)
for through-wall installation
xxx = 002 to 100
from 2 to 100 m cable length (about 6.5ft to 328ft)
max. temperature at sensors: 200°C (392°F)
probe length 250 mm - sintered steel filter

HygroClip IW-EX-xxx (intrinsically safe)
for surface mount (area monitoring)
xxx = 002 to 100
from 2 to 100 m cable length (about 6.5ft to 328ft)
max. temperature 40°C (104°F)
probe length 150mm

sintered steel filter

ZB1 Zenner Barrier for ID-EX and IW-EX

AC1617xxx Connecting Cable for ZB1

with built-in signal booster

xxx = 002 to 100

2 to 100m (about 6.5ft to 328ft)

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Use of analog probes is subject to the following restrictions and limitations:
a) ROTRONIC analog humidity-temperature probes with the standard temperature output signal of

– 0.5…2.0 V = -50…200°C: because the HygroFlex cannot read a negative voltage signal,
temperature measurement is generally limited to values above freezing.

b) Third-party analog probes: single channel probes (one signal), output signal within the range of

0 to 2.5 VDC, supply voltage: 15 VDC or less, maximum current consumption: 10 mA.

c) Resolution is limited by the 10-bit A/D converter used for the analog inputs. This converter

provides a theoretical maximum of 1024 counts for an input voltage span of 2.5 VDC. In theory,
this gives a resolution of 2.5 / 1024 = 0.00244 V. In practice, it is not possible to get 100% of the
counts from an A/D converter and the actual resolution should be about 0.0027 V (typical). For
example, if a probe with a temperature signal of 0..1 V = 0…100°C is being used, the signal
resolution will be about 100 x 1 x 0.0027 = 0.27°C

Analog Outputs (HygroFlex 1 and HygroFlex 3)

Model HygroFlex 1 HygroFlex 2 HygroFlex 3

analog outputs - relative humidity

- temperature

N/A

(digital output only)

- relative humidity

- temperature

- computed parameter

1)

output signals

2)

configurable with
jumpers

0…1 V
0…5 V
0…10 V
0…20 mA
4…20 mA

N/A 0…1 V

0…5 V
0…10 V
0…20 mA

4…20 mA
D/A output
resolution

humidity: 12-bit
temperature: 16-bit

N/A humidity: 12-bit

temperature: 16-bit

comp. parameter: 12-bit
options floating analog current

outputs

N/A floating analog current

outputs

16-bit D/A resolution for

the computed parameter

analog output, allows 0.1

resolution with a span of

more than 200 units.

1) The computed parameter and its range are set at the factory as specified when ordering. These
settings can be changed at any time with the optional HW3 software or with the optional display and
keypad. To prevent unauthorized or accidental changes, HW3 has provisions to block out access to
the computed parameter function from the keypad.

2) The output signals are set at the factory according to the type and range specified when ordering. A
label located on the transmitter housing shows the type of output signal for each unit.

The analog output signals are linear and are consistent with the requirements of most data/signal
processing instrumentation (panel meter, controller, computer card, etc.).

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RS232 Digital Port

The HygroFlex 1 has an internal RS232 service connector. Both the HygroFlex 2 and 3 have an
external RS232 connector (located on the connector plate). In principle, any communication
software can be used to interrogate and read the HygroFlex with the commands described in
appendix 7 (RS232 communication protocol). Use of the optional HW3 software simplifies this task.
It is important to note the following:

a) HygroFlex 1: use of the RS232 port (internal service connector) is limited to configuring the

instrument (units, range, etc.). Measurement data and calibration functions are not available on
this port.

b) HygroFlex 2 and 3: use the RS232 port to configure the transmitter, calibrate the probe and

connect the transmitter to a network. The computed parameter (dew point or other) is not part
of the digital communication (limited to %RH and temperature – in the unit selected for the
transmitter).

HW3 Software

The HW3 software (optional) allows real time computation of the dew point (or other) by the PC
while providing additional functionality such as:

- RS485 networking (up to 32 units)

- full access to instrument configuration (unit system, etc.)

- calibration of the ROTRONIC HygroClip digital probes with or without HygroFlex

- data logging to a PC disk file

- graphic functions (both on and off-line)

HW3 runs on any PC with Windows 98 or NT. For more details see separate instruction manual
provided with the HW3 software.

RS485 Networking (HygroFlex 2 and HygroFlex 3)

With the optional HW3 software up to 32 HygroFlex 2 or 3 transmitters can be connected together
on a network. Any transmitter can be used either as a slave or a master, without special
configuration. Each unit must be given a unique network address with the HW3 software (0 to 31).
The master is automatically the unit that is connected to the COM port of the PC by means of the
RS232 port. See Electrical Installation for details.

RS232: 3 wires (including ground wire)
RS485: 2 wires

PC

(HW3)

COM Port

Unit 0

Unit 1

Unit 31

RS232

RS485

RS485

RS485

RS232

RS232

RS232 up to 150m (490 ft)

RS485 up to 1000m (3300 ft)

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Unit System

The unit system of the HygroFlex (Metric or English) is factory programmed as specified when the
instrument was ordered. The unit system can be easily be changed by the user with the optional
HW3 software.

Optional Display and Keypad

The LC display shows which probe input is being displayed (small indicator on top of the display)
and up to 2 parameters measured by the probe, with the associated engineering unit. When
relevant, the message line provides additional information.

s s

zz 8.8:8.8 zzzz
zz 8.8:8.8 zzzz

zzzzzzzzzzzzzzzzz

Keypad

Humidity and Temperature
Calculated Value and Temperature
Calculated Value and Humidity

Probe Input Indicator

(1-2) from left to right

Engineering
Units

Message Line

Parameter

MENU : Press this key to activate the function menu. The different
menu items appear on the LCD message line. Press this key again
to exit the menu

UP / DOWN: Press one of these keys to select the probe input
for the display and functions. When the function menu is active,
use these keys to navigate the menu, make a selection or to
change a number on the display.

ENTER: When the menu is active, press
this key to confirm a selection.

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Installation

Mechanical Installation

Installation of the Transmitter Enclosure

The HygroFlex includes 5 parts that can be separated one from the other: wall plate (1), electronics
housing (2), electronics module (3), connector plate (4) and front cover with or without optional
display and keypad (5).

1) Attach the wall plate in the position shown above to an appropriate surface using 4 screws.

2) Slide the electronics housing down on the wall plate to the mechanical stop

To remove the cover, insert a screwdriver in the V-shaped slot on top of cover and press to
unlock prior to pulling the cover away from the electronics housing. If the cover has the optional
display and keypad, it is is connected to the electronics module by a ribbon cable that is
inserted in two zero-insertion-force connectors (see below).

Cover with optional Display and Keypad

Zero-insertion-force connectors are used both inside of the cover and on the electronics module.
With this type of connector, the ribbon cable can be disconnected by gently pulling on it. The cable
is connected simply by inserting it in the connector. To lock the connector and establish positive
contact, press down on the outside connector frame. Each end of the ribbon cable has non­insulated and an insulated side. The insulated side is indicated by the blue color. When inserting
the cable in the connector, pay attention to the position of the blue side of the flat ribbon cable as
indicated below. If the cable is disconnected and then reconnected while the transmitter is
powered, the display may become blank. In that case, unpower and power again the transmitter.

1

2

3

4

5

Electronics Module

Display
Connector

Blue side of

UP

Cover (inside)

Connector

Blue side of

UP

V-shaped
slot

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Probe Installation

Do not remove the dust filter or slotted cap from the probe. Both sensors can easily be damaged
when not protected

- Install the probe at a location where humidity, temperature and pressure conditions are
representative of the environment or process to be measured. Avoid the following: (a) Close
proximity of the probe to a heating element, a cooling coil, a cold or hot wall, direct exposure to
sun rays, etc. (b) Close proximity of the probe to a steam injector, humidifier, direct exposure to
precipitation, etc. (c) Unstable pressure conditions resulting from excessive air turbulence.

- If possible, choose a location that provides good air movement at the probe: air velocity of at
least 1 meter/second (200 ft/ minute) facilitates adaptation of the probe to changing temperature.

- When installing the probe through a wall, immerse as much of the probe as possible in the
environment to be measured.

OK

NG

NG

Small Diameter Duct

Short Probe

OK

NG

9 to 9.5" immersion

Position the probe so as to prevent the accumulation of condensation water at the level of the
sensor leads. Install the probe so that the probe tip is looking downward. If this is not possible,
install the probe horizontally.

Depending on the probe model, a probe holder (mounting flange with a compression fitting) can
facilitate installation through a wall.

Future maintenance can be made easier by providing next to the probe a calibration access orifice.
During maintenance, this permits the insertion of a reference probe (calibrator).The calibration
access orifice should have the same size as the orifice used to install the probe and can be
equipped with a probe holder.

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Electrical Installation

Terminal Blocks

The terminal blocks of the HygroFlex are of the plug-in type.
If the electronics module has to be removed from the enclosure, simply unplug the terminals from

the electronics module, without undoing the wiring.

Connection Plate

The configuration of the connection plate depends both on the model and on the options that were
ordered for the HygroFlex.

1) power and analog outputs: depending on the options, the connector plate may be equipped with cable grips,

with 1/2” conduit adapters or with connectors.

probe input 2 (optional / depends on model):

- third-party analog probe

- HygroClip probe with adapter cable

RS232 / RS485 (depends on model)

analog outputs

1)

(depends on model)

power

1)

probe input 1

- HygroClip probe

- analog probe with adapter cable

test (calibrator)

GND
DIO

AIN+
GND
DIO
V++

485 –
485 +
GND
RX
TX

AIN2+
AIN1+
GND
DIO

V++

OUT 1 +

OUT 2 +

OUT 3 +

GND

AC N / DC -

AC Ph / DC +

GND

probe input 1

test

probe input 2 (optional / depends on model)

RS232 / RS485

(optional / depends on model)

analog outputs (depends on model)

Power

Electronics Module

See also

connector diagrams

TB2: 4 3 2 1

TB1: 3 2 1

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The connectors are factory pre-wired to the terminal blocks of the electronics module. Depending
on the transmitter model and options, matching connectors are shipped together with the
transmitter. If the connector plate is equipped with cable grips or conduit adapters for the analog
outputs and power, the wiring connections to the electronics module have to be made at the time of
the installation.

Connector Diagrams

Probe 1 – TUCHEL (7-pin shown from solder side))

Pin # Function Pos. on Terminal Block (PCB)

E GND 3
1 Temperature – analog (+) 5
3 DIO (digital) 2
5 + VDC 1
6 Humidity – analog (+) 4

Test Connector (2-pin shown from solder side)

Pin # Function Pos. on Terminal Block (PCB)

1 DIO (digital) 1
2 GND 2

Probe 2 (5-pin shown from solder side) – optional (e.g. pressure)

Pin # Function Pos. on Terminal Block (PCB)

2 + VDC 1
3 GND 3
4 DIO (digital) 2
5 Analog (+) 4

RS232 / RS485 (5-pin shown from solder side)

Pin # Function Pos. on Terminal Block (PCB)

1 TXD 1
2 RXD 2
3 GND 3
4 RI + 4
5 RI - 5

Analog Outputs (4-pin shown from solder side) – optional

Pin # Function Pos. on Terminal Block (PCB)

1 Output 1 (+) 1
2 Output 2 (+) 2
3 Output 3 (+) 3
4 GND 4

RS232 connection (PC side)

Pin # Function

2 RX
3 TX
5 GND

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Electrical Diagrams (analog outputs)

Before making the electrical connections, be sure to correctly identify each connector and terminal.
Applying power to any of the input or output terminals can severely damage the transmitter.

12 to 35 VDC or 12 to 24 VAC supply voltage and voltage output signals

TB1 (2) 12…35 VDC (+) or 12…24 VAC neutral TB2 (1) Relative humidity (+)
TB1 (1) 12…35 VDC (-) or 12…24 VAC Ph TB2 (2) Temperature (+)
TB1 (3) Ground TB2 (3) Calculated Parameter (+)

TB2 (4) Common (-)

90…264 VAC with optional power module and current output signals

TB1 (2) 90…264 VAC Neutral TB2 (1) Relative humidity (+)
TB1 (1) Phase TB2 (2) Temperature (+)
TB1 (3) Ground TB2 (3) Calculated Parameter (+)

TB2 (4) Common (-)

RL

1)

RL

1)

RL

1)

1) minimum load:

1000 ohm

~

~

TB1 TB2

2

1

3

1
2

3

4

~

RL

1)

RL

1)

RL

1)

1) maximum load :
500 ohm
wiring included.

~

~

TB1 TB2

2

1

1

3

2
3

4

~

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Floating Current Outputs (option)

1) maximum load : 500 ohm, wiring included

Power Supply Cable

If the transmitter was supplied with cable grips, please note that the cable grips provide effective
sealing only with cables having the proper outside diameter. Preferably, use a cable with an outside
diameter of 6 to 7 mm (0.236 to 0.275”) and with 18AWG wires. Seal any unused cable grip. We
generally recommend grounding the HygroFlex, especially if the electronics will be subjected to a
low humidity environment (35 %RH or less).

Analog Signals Cable

Generally, we recommend running the analog signal cable separately from the power cable.
If the transmitter was supplied with cable grips, please note that the cable grips provide effective

sealing only with cables having the proper outside diameter. Preferably, use a cable with an outside
diameter of 6 to 7 mm (0.236 to 0.275”) and with 18AWG wires. Depending on the installation, you
may have to use a cable with twisted pairs or a shielded cable to avoid interference. Seal any
unused cable grip.

In order to determine the maximum length of cable that can be used to connect the transmitter to
other devices, the first step is to find out what is the resistance per unit of length of the cable that
you plan on using.

. Current outputs: the maximum permissible cable length, connecting the unit to other devices, is

determined by the total resistance resulting from the addition of the cable resistance and that of
the devices connected in series with the unit. This resistance should not exceed 500 ohms.

. Voltage outputs: the maximum cable length can be determined under consideration of the voltage

drop caused by the current flowing to the devices connected to the unit. The voltage drop in the
cable depends both on cable resistance and on the equivalent resistance of the devices
connected in parallel to the unit. The total resistance connected to each unit output must at least
be equal to 1000 ohm. Cable resistance should not be more than 1/1000 of the load resistance.

RL

1)

RL

1)

RL

1)

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Network Configuration and Wiring (HygroFlex 2 and HygroFlex 3)

The RS232 connection between the HygroFlex and a PC requires 3 wires: RX, TX and GND 1) .
Without a signal booster, the maximum cable length is limited to 150 m (490 ft).

1) GND is internally connected to the power ground of the transmitter

The RS485 wiring can be done with a twisted pair (2-wire, telephone type) and wall mounted RJ45
receptacles. No shielded cable and no terminator should be required.

AC1624

A 2-cable, 5-pin connector was supplied with each unit (see Connector Diagrams). Both the RS232
and RS485 wiring share this connector on the first unit (0). Be sure to observe the polarity for each
connection.

PC

COM

RS232 (3 wires)
maximum 150 m (490 ft)

RS485 ( 2 wires)
maximum 1,000 m (3,300 ft)
can be left open ended

RJ45

2 wires

2-cable

connector

Unit 0

Unit 1

Unit 2

Unit 31

Prior to networking the transmitters

, these should be individually configured with the HW3

software (see separate instructions on the HW3 CD ROM). Proceed as follows:

1) Connect each transmitter, one at a time, to the COM port of the PC

2) Assign to each transmitter a unique network address (a number between 0
and 31). By default, all transmitters are shipped by the factory with address 0.

3) For easier identification, you may also want to give at that time a descriptive name
(maximum 30 characters) to each transmitter.

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Configuration of the Analog Outputs

On the HygroFlex 1 and HygroFlex 3, the type of output signal can be selected by means of two
jumpers for each output. These jumpers are located on the PCB of electronics module:

Signal OUT1 OUT2 OUT3

1)

0…1 V B2, B3, B31 B12, B13, B31 B22, B23, B31
0…5 V B2, B4, B32 B12, B14, B32 B22, B24, B32
0…10 V B2, B5, B31, B32 B12, B15, B31, B32 B22, B25, B31, B32
0…20mA B1, B3, B33, B34 B11, B13, B33, B34 B21, B23, B33, B34
4…20mA B1, B3, B31, B33, B34 B11, B13, B31, B33, B34 B21, B23, B31, B33, B34

1) HygroFlex 3 only (computed parameter)
The scale (or range) of each analog output can be changed with the HW3 software (see separate

instructions). On the HygroFlex 3, the parameter corresponding to the third output can also be
changed with the HW3 software (see separate instructions).

Functions

The functions can be accessed either with the optional display and keypad or by connecting a
HygroPalm indicator to the Test connector of the HygroFlex (see Remote Mode). Some functions,
including all calibration functions, can also be accessed with the HW3 software.

To access the function menu from the HygroFlex keypad, press the MENU key. The first menu item
appears on the message line of the LC display. Use the UP or the DOWN key to navigate the
menu. When the desired menu item appears on the message line of the LC display, press the
ENTER key to select. Some menu items have sub-items. These can be selected with the UP,
DOWN and ENTER keys. To exit the menu and return to the normal display mode, press the
MENU key. The instrument also returns automatically to the normal display mode when no key is
being pressed for some time (main menu: 10 sec., submenu: 30 sec.).

B31
B32
B33
Res.

RS232 / RS485

HygroFlex 1: to configure the temperature range
and unit, use this 3-pin service connector and
connect to a PC with cable # AC1623.

HygroFlex 3: the transmitter can be configured
by connecting the RS232 / RS485 output to a
PC.

For both transmitters, configuration requires the
HW3 software installed on the PC.

B34

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CALCULATE (HygroFlex 2 and HygroFlex 3)

Definition

This function is used to select the humidity parameter that is calculated and displayed by the
instrument 1) . Any selection made here has no effect on analog output #3 (computed parameter) of
the HygroFlex 3. Use the HW3 software to change the computed parameter sent this output.

1) does not apply to third-party analog probes.

The calculated parameter is selected individually for each probe connected to the instrument 1).
Prior to entering this function, select on the display the probe input to programmed.

The unit system (Metric or English) is factory programmed according to what was specified when
the instrument was ordered. The unit system can be selected with the optional HW3 software (see
separate instructions).

Selections

Parameter M E HygroFlex 1 HygroFlex 2 HygroFlex 3

Dew Point / Frost Point

1)

°C °F

N/A

x x

Wet Bulb Temperature

°C °F

N/A

x x

Enthalpy J/g BTU/lb N/A

x x

Vapor Concentration g/m3gr/cuft N/A

x x

Specific Humidity g/kg gr/lb N/A

x x

Mixing Ratio g/kg gr/lb N/A

x x

Vapor Concentration
at Saturation

g/m3gr/cuft N/A

x x

Partial Pressure
of Water Vapor

hPa PSI

In Hg

N/A

x x

Saturation Pressure
of Water Vapor

hPa PSI

In Hg

N/A

x x

Pressure Constant

2)

(Barometric Pressure)

hPa PSI

In Hg

N/A

x x

1) The standard factory setting is frost point for values below freezing. This setting can be changed
to dew point with the optional HW3 software

2) This selection shows the fixed value that is used for computing the parameters that require
barometric pressure as an input. The fixed pressure value can be changed with the optional HW3
software. Both the HygroFlex 2 and HygroFlex 3 can also be programmed to accept the input from
a pressure probe (variable pressure value).

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DISPLAY (HygroFlex 2 and HygroFlex 3)

Definition

This function is used to select which parameters are displayed by the instrument. The display mode
is specified globally for all humidity probes connected to the instrument.

HygroFlex 3: the display selection has no effect on the analog outputs.

Selections

- Measurement
Relative humidity and temperature or the parameter measured by any third party probe

connected to the instrument.

- Calculated + Temperature
Calculated parameter (as selected under CALCULATE) and temperature. This selection is not

available with third-party probes.

- Calculated + Humidity
Calculated parameter (as selected under CALCULATE) and relative humidity. This selection is

not available with third-party probes.

ADJUST M.PT (2- to 4-point adjustment against a reference environment)

Definition

The Adjust M.PT function permits to calibrate and adjust a ROTRONIC HygroClip digital probe
against a known reference environment. This function is designed to permit calibration at 2
temperature values and at up to 4 relative humidity values.

Selections

The Adjust M.PT function offers the following selections:
RHS: Humidity calibration using the ROTRONIC Humidity Standards

1)

Humidity: Humidity calibration using any suitable reference environment
Temperature: Temperature calibration using any suitable reference environment

1) For humidity calibration, ROTRONIC offers convenient, certified humidity standards to generate known

humidity values (for more details, see Appendix 3 - Humidity Calibration).

Procedure

When two probes are connected to the transmitter, be sure to select on the display the HygroClip
probe to be calibrated prior to entering the function.

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Regarding the Adjust M.PT function, it is important to observe the following rules:
a) Always calibrate temperature first (if temperature needs to be calibrated)
b) When calibrating temperature (2 points), always calibrate at the low value first. The instrument is

programmed to use the low temperature value to compute the offset and the high temperature
value to compute the gain.

T-low < 70 °C (158°F) : used to compute the calibration offset
T-high = 70 °C (158 °F) : used to compute the calibration gain

For best accuracy, we recommend using a T-low value close to 20°C (68°F). Preferably, the
difference between T-high and T-low should be at least 50 °C (90 °F)

c) When calibrating relative humidity (2, 3 or 4 points) with the ROTRONIC humidity standards,

always follow the sequence 35 %RH, 80 %RH, 10 %RH or 5 %RH, 0 %RH. When using a
reference other than the ROTRONIC humidity standards, use reference conditions that are
within the following brackets and observe the sequence:

>25 %RH…=55 %RH

1)

: used to compute the calibration offset
>55 %RH 1) : used to compute the calibration gain
>1 %RH…=25 %RH : sensor linearity adjustment
= 1 %RH : sensor linearity adjustment

The HygroFlex is programmed to automatically recognize these brackets.

1) For best accuracy, we recommend using values close to 35 %RH and 80 %RH
When the probe is at equilibrium with the reference environment, activate the Adjust M.PT function

and make the appropriate selections:
a) RHS: press the ENTER key to select this item. The LC display shows the value of the standard

(for example 35.0%RH) on the top line and “Humidity RHS” on the message line. Verify that the
value agrees with the standard being used. If necessary, change the value of the standard with
the UP or the DOWN key. Press the ENTER key when done.

Note: the software automatically compensates for the effect of temperature on the humidity
standard. No additional correction is required.

b) Humidity or Temperature: press the ENTER key to select. The LC display shows the value

read by the probe at the time the ENTER key was pressed. The word “humidity” or
“Temperature” is shown on the message line. Use the UP or the DOWN key to change the
humidity or temperature value to match the value of the reference environment. For a faster
change, keep the key pressed down. Press the ENTER key when done.

After pressing the ENTER key, the message “sure?” should appear on the LC display. Press
ENTER to confirm. Next, the LC display will confirm that the probe adjustment has been
successfully completed. At that time, press ENTER to exit or MENU to return to the function Adjust
M.PT and do another calibration point.

Carry on in the same manner for each calibration point, following the sequence described above.
Note: you can exit the function at any time (without calibrating the probe) by pressing the MENU

key.

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ADJUST 1PT (1-point adjustment against a reference environment)

Definition

The Adjust 1PT function permits to do a 1-point adjustment (offset adjustment) of a ROTRONIC
HygroClip digital probe against a known reference environment. This function is limited to a simple
offset adjustment that is applied across the entire measuring range.

Warning: a 1-point adjustment is no substitute for an adjustment at 2 or more points. Adjusting the
probe at only one value can improve accuracy over a narrow range of conditions and may also be
detrimental to accuracy at other conditions.

Selections

The Adjust 1PT function offers the following choices:
RHS: Humidity calibration using the ROTRONIC Humidity Standards

1)

Humidity: Humidity calibration using any suitable reference environment
Temperature: Temperature calibration using any suitable reference environment

1) For humidity calibration, ROTRONIC offers convenient, certified humidity standards that generate known
humidity values (for more details, see Appendix 3 - Humidity Calibration).

Procedure

When two probes are connected to the transmitter, be sure to select on the display the HygroClip
probe to be calibrated prior to entering the function.

When the probe is at equilibrium, activate the Adjust 1PT function and make the appropriate
selections:

a) RHS: press the ENTER key to select this item. The LC display shows the value of the standard

(for example 35.0%RH) on the top line and “Humidity RHS” on the message line. Verify that the
value agrees with the standard being used. If necessary, change the value of the standard with
the UP or the DOWN key. Press the ENTER key when done.

Note: the software automatically compensates for the effect of temperature on the humidity
standard. No additional correction is required.

c) Humidity or Temperature: press the ENTER key to select. The LC display shows the value

read by the probe at the time the ENTER key was pressed. The word “humidity” or
“Temperature” is shown on the message line. Use the UP or the DOWN key to change the
humidity or temperature value to the value of the reference environment. For a faster change,
keep the key pressed down. Press the ENTER key when done.

After pressing the ENTER key, the message “sure?” should appear on the LC display. Press
ENTER to confirm. Next, the LC display will confirm that the probe adjustment has been
successfully completed. At that time, press ENTER to exit.

Note: you can exit the function at any time (without calibrating the probe) by pressing the MENU
key.

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ADJUST REF (1-point adjustment against a reference probe)

Definition

Note: this function is not available with the HygroFlex 1 (single probe input).
When two ROTRONIC HygroClip digital probes are connected to the HygroFlex, the Adjust REF

function permits to do a 1-point adjustment (both humidity and temperature) of one of the probes,
using the other probe as a reference.

Warning: a 1-point adjustment is no substitute for a full calibration (2 or more points). Doing a 1­point adjustment can improve accuracy over a narrow range of conditions and may also be
detrimental to accuracy at other conditions.

Procedure

Prior to entering the function, select on the display the probe to be adjusted. The other probe is
automatically the reference probe.

Expose both probes to the same stable environment. Ventilation of the probes is highly
recommended. Observe the readings from both probes for complete equilibration with the reference
environment .

Press the ENTER key to enter the function. The display asks you to wait for a short time and then
shows the temperature and humidity read by the reference probe at the time the ENTER key was
pressed. Note that these values are not updated to the display as long as the function is active. The
message line of the display shows which probe is the reference: for example REF = Probe 2
indicates that probe #2 is the reference.

Press the ENTER key to accept. After pressing the ENTER key, the message “sure?” should
appear on the LC display. Press ENTER to confirm. Next, the LC display will confirm that the probe
adjustment has been successfully completed. At that time, press ENTER to exit.

Note: you can exit the function at any time (without calibrating the probe) by pressing the MENU
key.

PROBE

Definition

This function displays the version number and serial number of any ROTRONIC HygroClip digital
probe connected to the instrument.

Procedure

Prior to entering the function, select the probe to be displayed (this is the same as the probe that
was last displayed).

When entering the function, the version number of the probe is displayed first. Use the UP or the
DOWN key to display the serial number of the probe.

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RS STATUS

Definition

This function displays the network address of the instrument (preceded by a letter indicating the
type of instrument) as well as the RS232 configuration: baud rate, parity, number of data bits,
number of stop bits.

Procedure

When entering the function, the network address is displayed first. Use the UP or the DOWN key to
display the RS232 configuration of the instrument.

SYS STATUS

Definition

This function displays the software version of the instrument, the serial number of the instrument,
the user defined name associated with the instrument (this is entered with the HW3 software) as
well as any coded error message (see table below).

Procedure

When entering the function, the software version number is displayed first. Use the UP or the
DOWN key to display the other data.

Errors and Status Messages

Errors:

101

checksum error the checksum test did not pass during RS-communication.

102

bad command an unknown command was received

103

disallowed command a command was received that is reserved for production

and service

104

unknown probe input reference was made to a non-existing analog or digital

probe input

105

argument error error in the number of the arguments in the command or in

the value of one of the arguments

106

HygroClip
communication error

the HygroClip probe does not answer or is not connected

107

calibration error the difference between the probe reading and the

calibration point is larger than the maximum allowed by the
INI command.

108

calibration error
(overflow)

internal probe error (or the difference between the probe
reading and the calibration value is too large)

110

unknown reference
probe

the reference probe is not connected or the reference probe
input does not exist

111

Temperature error During humidity calibration, temperature should be within

the limits of 0 and 80°C (32 and 176°F)

Warnings:

120

no adjustment calibration

121

No HygroClip probe is
connected

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Status:

130

the probe was
adjusted

calibration

Calibration with a HygroPalm Indicator

Definition

The Remote Control Mode of the HygroPalm indicator is especially useful when the transmitter
does not have the optional display and keyboard. Depending on the model of HygroPalm, the
Remote Control mode allows the following:

HygroPalm1HygroPalm2HygroPalm

3

Display the readings from any probe connected to the
transmitter

x x x

Display the transmitter status
(configuration, serial number, etc.)

N/A

x x

1-point adjustment of any ROTRONIC HygroClip
digital probe connected to the transmitter, using the
probe connected to the HygroPalm as a reference

N/A

x x

Access the functions 1) of the transmitter, primarily the
ADJUST M.PT function - see Functions.

N/A N/A

x

1) except for CALCULATE and DISPLAY

Procedure

The Remote Control mode is automatically activated by connecting any probe
input of the HygroPalm to the Test port of the transmitter (use cable # AC1621).

As soon as the two instruments are connected, the HygroPalm detects the
transmitter and this is indicated by a flashing star on each side of the LC
display. At that time, the display of the HygroPalm shows data from the remote
unit and can no longer be used to access local data from the HygroPalm.
Similarly, the function keys of the HygroPalm control the transmitter and not the
HygroPalm itself.

To exit the Remote Control mode, simply disconnect the two instruments.
Note: using the Remote Control mode does not disturb the output signals

(analog or digital) of the transmitter. The outputs keep being normally updated.

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Display the Transmitter Measurements

As soon as the Remote Control mode is initiated, the HygroPalm displays the measurements from
the probe(s) connected to the transmitter. When two probes are connected to the transmitter, each
probe can be displayed with the UP or DOWN key on the HygroPalm.

Functions (except ADJUST M.PT and ADJUST 1PT)

Press the MENU key of the HygroPalm to access the functions of the transmitter and use the UP
and DOWN keys to navigate the function menu. Selections are confirmed by pressing the ENTER
key.

Access to the functions depends on the model of HygroPalm. The functions CALCULATE and
DISPLAY are generally not accessible in the Remote Control mode. For more details see Functions

Functions ADJUST M.PT and ADJUST 1PT

The functions ADJUST M.PT 1) and ADJUST 1PT 1) can be accessed only with the HygroPalm 3. In
the remote mode, both the display and the keyboard of the HygroPalm act like if they were the
display and keyboard of the remote unit. The definition of these functions and the procedure to be
followed are the same as already described under Functions.

1) applies only to the ROTRONIC HygroClip digital probes

Function ADJUST REF

In the Remote Control Mode, the function Adjust REF can be used to do a 1-point adjustment of the
ROTRONIC HygroClip probe(s) 1) connected to the transmitter against the probe connected to the
HygroPalm indicator. The function adjusts both humidity and temperature simultaneously.

The following choices are available for the reference probe:
a) REF = PALM: the reference is the probe connected to any probe input of the HygroPalm (the

other probe input of the HygroPalm is already used to connect to the TEST port of the
transmitter).

b) REF = TRANS: the reference is always the probe connected to input 2 of the transmitter of the

probes connected to the transmitter. Probe #1 will be adjusted to match the reference probe.

1) When no such probe is detected, the message “connect fail” will be displayed.

Press MENU and use the UP or the DOWN key to access Adjust REF from the function menu.
Press ENTER to select this function.

After pressing the ENTER key, the display of the HygroPalm shows the relative humidity and
temperature data from the reference probe. The message REF = PALM or TRANS should also
appear on the LC display. Use the UP or the DOWN key to select one the these two choices. The
data on the display is the data read by the reference probe at the time the ENTER key was
pressed. This data is not updated while the function Adjust REF is active (see Notes below).

Press the ENTER key to accept the reference data. The message “sure ?” should appear on the LC
display. Press ENTER to do the 1-point adjustment of both humidity and temperature or press
MENU to abort and exit this process. When the message “Adjust OK” appears, press ENTER to
exit.

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Notes:
Expose both probes to be to the same stable environment. Ventilation of both probes is highly

recommended. Observe the readings from both probes for complete equilibration (this can be done
by entering and exiting a few times the function Adjust REF so as to check both probes prior to
adjusting).

If the transmitter has its own display, it simply repeats the data or commands shown on the display
of the HygroPalm.

Environmental Limits

The HygroFlex can operate in the temperature range of –40...60°C (-40…140°F) and should not be
exposed to condensing humidity. Units with the optional LC display and keypad should not be used

below -30°C (-22°F).
The operating limits at the probe depend on the probe model and are specified separately for each

probe.

Maintenance

On-Site Maintenance

a) Probe maintenance:

Each HygroFlex transmitter has a test connector that is located on the connection plate.
The HygroPalm 3 portable indicator can be connected to this connector with cable
AC1621. Using the probe of the HygroPalm as a reference, any HygroClip digital probe
connected to the transmitter can be read and adjusted at one humidity and temperature
value. When adjusting against a reference probe, please make sure that both probes are
exposed to the exact same environment and are at temperature and humidity equilibrium.
Ventilation of both probes (same air stream) is highly recommended.

b) Validation of the analog outputs

With the exception of the analog probe input and analog output circuits, the HygroFlex
uses digital circuits that are by nature immune from drift. The HygroFlex uses analog
circuits that are very stable. These circuits should not exhibit any noticeable drift for many
years. If so desired, the analog input and output circuits can be validated by substituting a
test connector for the probe. The test connector AC1618/50 simulates a HygroClip probe

and generates digital and analog signals corresponding to 50%RH and 25°C (77°F). The
output signals can be read with a DVM (open the transmitter housing and disconnect the
analog output plug-in terminal block).

Factory / Metrology Lab. Maintenance

The HygroFlex should not require any routine maintenance other than validating the analog probe
inputs (if used) and the analog outputs. Please, contact the factory if the analog outputs require an
adjustement. See appendix 3 and appendix 4 regarding the maintenance of the humidity
temperature probes used with the HygroFlex.

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Specifications

Operating Voltage standard 12 to 35 VDC / 300 mA max.

or 12 to 24 VAC

optional 90 to 264 VAC 50/60 Hz

Operating limits at electronics 0…99 %RH (non condensing)

w/o LC display -40...60°C (-40...140°F)
with LC display -30…60°C(-22…140°F)

Measured parameters

1)

relative humidity typical range 0…100 %RH

indication range 0.0 to 100.0 %RH

temperature typical ranges 0…100 °C, -50…150°C, 0…200°C

0…100 °F, -50…250°F, 0…400°F

indication range -99.9 to 999.9 °C or °F

barometric pressure

2)

typical range 0…2000 hPa / 0…50 PSI / 0…100 InHg

indication range 0.000 to 9999 hPa/PSI/InHg

Calculated parameters

1) 2)

dew / frost point

3)

typical range -50…100 °C / -50…200°F
indication range -99.9 to 999.9 °C or °F

wet bulb temperature

4)

typical range 0…100°C / 0…200°F
indication range 0.0 to 100.0°C / 32 to 212.0°F

enthalpy

4)

typical range -50…250 J/g or -50..150 BTU/lb
indication range -99.9 to 9999 J/g or BTU

vapor concentration typical range 0…500 g/m3 or 0…250 gr/cuft

indication range 0.000 to 9999 g/m3 or gr/cuft

specific humidity

4)

typical range 0…500 g/kg or 0…4000 gr/lb
indication range 0.000 to 9999 g/kg or gr/lb

mixing ratio

4)

typical range 0…500 g/kg or 0…4000 gr/lb
indication range 0.000 to 9999 g/kg or gr/lb

vapor concentration at saturation typical range 0…500 g/m3 or 0…250 gr/cuft

indication range 0.000 to 9999 g/m3 or gr/cuft

part. pressure of water vapor typical range 0…500 hPa / 0…10 PSI / 0…20 InHg

indication range 0.000 to 9999 hPa / PSI / InHg

sat. pressure of water vapor typical range 0…500 hPa / 0…10 PSI / 0…20 InHg

indication range 0.000 to 9999 hPa / PSI / InHg

System accuracy at 23°C/73°F ± (0.5%RH + 1.5% of reading)
with HygroClip probe & 4-point calibration ± 0.2°C / 0.4°F

Number of probe inputs HygroFlex 1 1

HygroFlex 2 and 3 1 (standard) or 2 (optional)

Probe type

5)

all models ROTRONIC HygroClip digital probe
HygroFlex 2 and 3 ROTRONIC analog probe

6)

Third-party analog probe

6)

Analog outputs (scalable) HygroFlex 1 2: relative humidity and temperature

HygroFlex 3 3: relative humidity, temperature

and calculated parameter

7)

Analog signals (selectable) HygroFlex 1 and 3 0…1V, 0…5V, 0…10V

0…20 mA, 4…20 mA
Minimum load for voltage outputs 1000 ohm
Maximum load for current outputs 500 ohm

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Serial output

8)

HygroFlex 1 RS232 (internal service connector)
HygroFlex 2 and 3 RS232 / RS485 (external connector)

Electrical Connections power cable grip and terminals

9)

analog outputs cable grip and terminals

9)

serial output connector

10)

probe input(s) connector

11)

Optional LC display and keypad alphanumerical, 0.000…9999

membrane keypad
Housing Material ABS (standard)

metal (option)
Housing Dimensions 207 x 150 x 59 mm (8.15 x 5.91 x 2.32”)
Weight 800 g (1.76 lb)
Protection grade IP65 / NEMA 4

1) Specify engineering units and range when ordering (both can be changed by user with optional HW3

software). See separate probe specifications regarding the different range limits

2) Not available with the HygroFlex 1. The accuracy of the computed parameter is limited by the accuracy of

the measured parameters on which it is based

3) The standard factory setting is frost point for values below freezing. This setting can be changed to dew

point with the optional HW3 software

4) A fixed value is used for the computations of this parameter. The fixed pressure value can be changed by

the user with the optional HW3 software. The HygroFlex can also be programmed to accept the input from
a pressure probe (variable pressure value)

5) Accuracy, repeatability and operating limits are specified separately for each model of probe

6) ROTRONIC analog probes: because the HygroFlex cannot read a negative input voltage, temperature

measurement with probes having a standard output is generally limited to values above freezing. Third­party probe (pressure or other): linearized voltage output signal within the range of 0..2.5 VDC, supply
voltage 15 VDC, 10 mA

7) The span of the computed parameter should be determined under consideration of the D/A resolution of

the corresponding analog output (12-bit is standard for output # 3). Depending on the desired signal
resolution, a wide span may require the optional 16-bit D/A converter for analog output # 3

8) RS485 network: requires the first transmitter to be connected to the RS232 COM port of a PC

9) ½” conduit adapters or connectors also available. Recommended cable for cable grips: 7..9 mm diameter

( 0.275..0.354”) with 18 AWG wires. Cable for output signals should preferably be shielded.

10) This is a 5-pin connector that is shared by the RS232 and RS485 signals. A matching 2-cable connector

is supplied with the transmitter

11) Supplied with the probe

Dimensions in mm

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Appendix 1: Practical Advice for Measuring Humidity

The most common source of error when measuring relative humidity is a difference between the
temperature of the probe and the temperature of the environment. At a humidity condition of 50
%RH, a temperature difference of 1°C (1.8 °F) typically results in an error of 3 %RH on relative
humidity.

To avoid temperature errors, insert as much of the probe as possible in the environment to be
measured. If the probe is short, you may have to insert not only the probe itself but also some of
the probe cable. Use the probe configuration that fits best for your application. Please also note
that some probes such as the HygroClip IE (measurement in compressed air) are not designed
to handle any significant temperature gradient between both sides of the mounting wall.

In extreme situations, condensation may occur on the sensors when the probe is colder than the
environment. As long as the humidity / temperature limits of the humidity sensor are not
exceeded, condensation does not alter the calibration of the sensor. However, the sensor has to
dry out before it can provide a valid measurement.

Non-moving air is an excellent insulator. When there is no air movement, surprising differences in
temperature and humidity can noted over short distances. Air movement at the probe generally
results in measurements that are both faster and more accurate.

Appendix 2: Resolution of the Analog Signals

The HW3 software allows to define the range of the analog output signals of the HygroFlex 3.
When selecting a range, it is important to consider the fact that the resolution of the analog output
signal depends on the span of the selected range.

The HygroFlex 3 uses two 12-bit D/A converters to generate the analog output signals for relative
humidity (output #1) and for the computed parameter (output #3). In theory, a 12-bit D/A converter
can distinguish between 4,096 values (or counts). This number of counts, together with the span of
the signal (%RH, °C, etc.), determines the resolution of the analog output signal.

Because of the tolerance in the analog components associated with the D/A converter, the number
of counts that are effectively used tends to be less than the theoretical maximum. Typically, only
about 90% of the counts (3,680) may be effectively used.

In addition, the analog output signal may be a partial range. For example, 4…20 mA is a partial
range of 0…20 mA. With a 4…20 mA output signal, the number of useful D/A counts is further
reduced by 20% (1 - 16/20) and only 72% of the count (2,950 counts) may be effectively available.

Taking the example of a 4…20 mA output, the span of the analog signal should not exceed 140 to
150 units (for example –50 to 100°C dew point) to maintain a resolution of 0.1 unit. With analog

signal such as 0…5V or 0…20 mA, a maximum span of 180 units could be used.
The above examples are based on a resolution of 0.05 units as this prevents the analog output

signal from bouncing around by ± 0.1 units.
For the temperature analog output signal, the HygroFlex 3 uses a 16-bit D/A converter. This is

more than sufficient to offer 0.1 resolution for any temperature range and any type of analog signal
available with the HygroFlex 3.

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Appendix 3: Maintenance of the ROTRONIC probes

Cleaning or Replacing the Dust Filter of the Probe

Most ROTRONIC probes come with one of the following types of dust filter: (a) protective
metal base with a removable filter cartridge or (b) plastic slotted cap with built-in (not
removable) filter element.

Depending on the conditions of measurement, the filter should be checked from time to time. If
the probe has a removable filter cartridge, this can be easily removed for cleaning.

If the probe has a plastic slotted cap with a built-in filter element, cleaning should be done
without removing the filter from the probe. In that case, do not use detergents, solvents or
other strong chemicals. Either brush the filter or use a little bit of clean water.

Corroded, discolored or clogged filters should be replaced. If the probe has a removable
cartridge, simply replace the cartridge (leave the metal base on the probe).

If the probe has a plastic slotted cap with built-in filter element follow these instructions:

1) Unscrew the filter from the probe and pull it straight away, in the alignment of the probe, so
as not the catch the humidity and temperature sensors.

2) Before putting on a new dust filter, check the alignment of both sensors with the probe. The
wires that connect the sensors to the probe are very thin and bend easily. If necessary, correct
the alignment by tapping the sensor very gently with a smooth object such as a small plastic
rod. Do not use sharp pliers or tweezers as this could puncture the sensor and do not pull hard
on the sensor.

Periodic Calibration Check of the Probes

Long term stability of the ROTRONIC Hygromer humidity sensor is typically better than 1 %RH
per year. For maximum accuracy, calibration of the probe should be verified every 6 to 12
months. Applications where the probe is exposed to significant pollution may require more
frequent verifications.

Both the Pt 100 RTD temperature sensor and associated electronics are very stable and
should not require any calibration after the initial factory adjustment.
For routine calibration checks, the probe should be verified at one or two values of humidity.
For more details, see appendix 4 - Calibration Basics and Functions – ADJUST M.PT.

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Appendix 4: Calibration Basics

Depending on whether or not the transmitter has a display and keypad, the following choices are
available to calibrate the probe(s) used with the HygroFlex:

a) Calibration using the transmitter display and keypad (see Functions)
b) Calibration using a HygroPalm indicator (see Remote Control with the HygroPalm indicator)
c) Calibration using a PC with the optional HW3 software (see separate instructions for the HW3

software) – This choice is available only with the HygroFlex 2 and HygroFlex 3.

d) Calibration of the probe alone (removed from the transmitter), using a PC with the optional HW3

software and the T7-03-WIN calibration cable (see separate instructions for the HW3 software).

Note: the HygroFlex itself should not require any field calibration.

Temperature Calibration

Note: the stability of the Pt100 RTD sensor used to measure temperature is such that
temperature calibration in the field is seldom required.

In order to be able to correctly evaluate the accuracy of the temperature measurements
provided by the probe, you should be able to meet the following requirements:

a) Both the probe and a reference thermometer should be ventilated with the same stream of

air. Any dust filter used to protect the sensors should be carefully removed from the probe.
If the probe has a protective slotted cap, this may be left on the probe.

b) Air velocity at the sensor should be within the limits of 200 to 500 feet/minute (1 to 2.5

meters/second). Any comparison between two instruments at a velocity under 200
feet/minute may not be valid. Air velocity above 500 feet/minute may damage the

unprotected humidity sensor.
c) The temperature of the air stream should be practically constant.
If you cannot meet the above requirements, you should not attempt to calibrate temperature.

Humidity Calibration

ROTRONIC provides easy-to-use, certified humidity standards for those customer who do not
have access to a humidity generator. To use these standards, you will need a calibration
device that is suitable for your probe.

Calibration Device

The calibration device is a small airtight container that fits on the probe and seals around the
humidity sensor. During calibration, a known reference humidity is produced inside the
calibration device by means of a humidity standard (usually an aqueous salt solution).

The following calibration devices are available from ROTRONIC:
ER-15: for 15mm diameter probes

ER-05: for 5 mm diameter probes
EM-15 for probe type IE
ERV-15 for probe type IW

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Certified Humidity Standards

The ROTRONIC certified standards are available in boxes of 5 glass ampoules of the same
value, which can be stored indefinitely. Standards in the range of 5 to 95 %RH are non­saturated aqueous salt solutions that are precisely titrated at our factory for the right
concentration. The 0 %RH humidity standard is made of small granules of a highly porous
ceramic that have been dried at a high temperature. A Material Safety Data Sheet is available
for each standard. Since most standards are a salt solution, parts which have come in contact
with the liquid should be cleaned after each use.

Each box of standards comes with a certificate that provides statistical information on the
manufacturing batch of the standard. Information on the effect of temperature on each
standard is provided on the cover of each box of standard. When calibrating either with the
HygroFlex or with the HW3 software, the effect of temperature on the standards is
compensated by the software and no further correction is required. The value of the standards
is not affected by altitude.

Instructions for using the Standards

• Install the calibration device on the probe so that the receptacle (or solution holder) is

under the probe. Check for a tight fit and remove the receptacle from the calibration device.

• Place one fiber disc (each box of standards includes 5 discs) in the receptacle of the

calibration device. The purpose of this disc is to prevent accidental spilling of the solution
inside the calibration device or on the humidity sensor.

• Tap the top of the ampoule so that all liquid drops to the bottom of the ampoule. Snap off

top and empty contents on fiber disc. Since the ampoule is made of glass, exercise proper
caution (gloves, safety glasses) when snapping off the top.

• Put the receptacle back on the calibration device and make sure that the solution does not

come in contact with the sensor: The solution inside the calibration device should never be
on top of the sensors.

• Allow at least 60 minutes to insure that the calibration device, the solution and the sensor

are in a state of equilibrium. This is verified by monitoring the display.

• After adjusting the probe, remove the receptacle from the calibration device. Throw away

the wet disc (non reusable). Thoroughly wash and wipe dry the receptacle.

General Recommendations

During calibration, temperature stability is the single most important requirement. If possible,
calibrate the probe is room temperature (18 to 25°C). Room temperature should be stable to ±

0.25°C or better during the period of time required for each calibration point. Do not calibrate
close to an air vent or a heater, in direct exposure to sun rays, etc.

If using a humidity generator to calibrate the probe, make sure that the probe is as fully
immersed in the generator as possible to minimize temperature effects.

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Appendix 5: Humidity Definitions

Relative Humidity

Relative humidity is the ratio of two pressures: %RH = 100 x p/ps where p is the actual partial
pressure of the water vapor present in the ambient and ps the saturation pressure of water at the
temperature of the ambient.

Relative humidity sensors are usually calibrated at normal room temperature (above freezing).
Consequently, it generally accepted that this type of sensor indicates relative humidity with respect
to water at all temperatures (including below freezing).

Ice produces a lower vapor pressure than liquid water. Therefore, when ice is present, saturation
occurs at a relative humidity of less than 100 %. For instance, a humidity reading of 75 %RH at a
temperature of -30°C, corresponds to saturation above ice.

Dew Point / Frost Point Temperature

The dew point temperature of moist air at the temperature T, pressure Pb and mixing ratio r is the
temperature to which air must be cooled in order to be saturated with respect to water (liquid).

The frost point temperature of moist air at temperature T, pressure Pb and mixing ratio r is the
temperature to which air must be cooled in order to be saturated with respect to ice.

Wet Bulb Temperature

The wet bulb temperature of moist air at pressure Pb, temperature T and mixing ratio r is the
temperature which the air assumes when water is introduced gradually by infinitesimal amounts at
the current temperature and evaporated into the air by an adiabatic process at constant pressure
until saturation is reached.

Vapor Concentration

The vapor concentration (density of water vapor in a mixture) or absolute humidity, is defined as the
ratio of the mass of water vapor Mv to the volume V occupied by the mixture.

Dv = Mv / V , expressed in grams/m3 or in grains/cu ft
This can be derived as follows from the equation PV = nRT:

a) Mv = n x mw, where :
n = number of moles of water vapor present in the volume V

mw = molecular mass of water
b) Dv = Mv /.V = n x mw / V = mw x p / RT , where:
mw = 18.016 gram

p = partial pressure of water vapor [Pa]
R = 8.31436 Pa x m3 / °K x mole
T = temperature of the gas mixture in °K

Dv [g / m3] = p / 0.4615 x T
1 gr (grain) = 0.0648 g (gram)

1 cu ft = 0.0283168 m

3

Dv [gr / cu ft] = 0.437 x Dv [g / m3]

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Specific Humidity

The specific humidity (also known as mass concentration or moisture content of moist air) is the
ratio of the mass Mv of water vapor to the mass (Mv + Ma) of moist air in which the mass of water
vapor Mv is contained.

Q = Mv / (Mv + Ma)
Q = p mw / (p mw + (Pb – p) ma)
Q [ g / kg] = 1000 p / (1.6078 Pb – 0.6078 p)
1 gr (grain) = 0.0648 g (gram)

1 lb = 0.4535923 kg
Q [gr / lb] = 7 x Q [g / kg]

Mixing Ratio by Weight

The mixing ratio r of moist air is the ratio of the mass Mv of water vapor to the mass Ma of dry air
with which the water vapor is associated:

r = Mv / M

a

Mv = n x mw = mw x p V / RT
Ma = n x ma = ma x pa V / RT = ma x (Pb – p) / RT, where:
mw = 18.016 gram

ma = 28.966 gram
p = partial pressure of water vapor [Pa]
pa = partial pressure of dry air [Pa]
Pb = total or barometric pressure [Pa]
R = 8.31436 Pa x m3 / °K x mole
T = temperature of the gas mixture in °K

r = mw p / ma (Pb – p)
r = 621.97 x p / (Pb – p) [g / kg]
1 gr (grain) = 0.0648 g (gram)

1 lb = 0.4535923 kg
r [gr / lb] = 7 x r [g / kg]

Enthalpy

The enthalpy (or energy content) of moist air at pressure Pb, temperature t (°C) and mixing ratio r
(g/kg) is defined by:

h [kJ / kg moist] = 1.00464 t + 0.001846 r x t + 2.5 r
Note: by convention, the enthalpy of dry air ( r = 0 ) at 0°C is equal to zero. Negative values of

enthalpy are possible and indicate that the energy content of the air / vapor mixture is less than the
energy content of dry air at 0°C

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1 lb = 0.4536 kg
1 BTU = 1.05507 kJ

h [BTU / lb] = 0.4299 x h [kJ / kg] + 7.68
The value 7.68 is added to reference enthalpy in BTU / lb to the temperature of 0°F.

Appendix 6: Dew Point Accuracy

Both the HygroFlex 2 and the HygroFlex 3 use the relative humidity and temperature
measurements to compute another parameter such as dew point, mixing ratio, enthalpy, etc. The
accuracy of this conversion varies, depending on the humidity and temperature conditions. Typical
accuracy for the dew point conversion is provided in the graph below:

Dew Point Accuracy

-60

-50

-40

-30

-20

-10

0

-40 -20 0 20 40 60 80 100 120

Temperature °C

Dew Point Depression °C

±1 °C

±1.5 °C

±2 °C

±2.5 °C

The accuracy of the dew point conversion is less than the accuracy that is normally achieved with a
chilled mirror instrument. This is especially true at low dew point values (dew point depression of
more than -40…-50°C) and at low temperatures. In many applications, repeatability is more critical
than accuracy. Repeatability of the dew point conversion is typically 1/3 of the accuracy shown
above.

Using a dew point conversion permits to measure conditions that cannot be measured with a chilled
mirror instrument. Typically, the measuring head of a chilled mirror instrument is limited to a
maximum of 70°C and, therefore, cannot measure a dew point temperature above 70°C. In addition
to the ability to operate at high temperature, the relative humidity probe offers significant
advantages for industrial applications: less maintenance and higher tolerance to contaminants, no
sampling system, no uncertainty between dew and frost and better response to fast changing
conditions.

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Appendix 7: RS232 Communication Protocol

The following describes the RS232 communication protocol that is used by the instruments from
ROTRONIC when connected to the COM port of a PC. This information is provided for those
customers who for some reason cannot use the HW3 software.

Connections

The exchange of data requires 3 wires: TXD (transmit), RXD (receive) and SG (signal ground).
When the instrument requires power from the COM port (MOK-WIN), the RTS and DTR wires are
also used.

RS232 Settings

Communication is done at the rate of 19200 bps. When there is a large amount of data to be
exchanged (file read), the baud rate can be increased to 38400 bps.

In principle, only 7-bit ASCII characters (ASCII 32 to 127) are being used. The exception is File
Read, where 8-bit characters are being used.

Normal settings:
Baud rate : 19200

Parity : even
Data bits : 7
Stop bits : 1
Flow Control : none

Force incoming data to 7-bit ASCII.

Data Integrity

- 7-bit characters are sent with a parity bit. 8-bit characters are sent without parity bit.

- Strings (made of 7-bit characters) can be sent with or without checksum at the end of the string.

When the checksum is not known – for example: when sending a command - the checksum is

replaced by the } character at the end of the string.

- For the transmission of files (8-bit characters), we plan on using predefined initialization and

end-of-communication sets of characters with a checksum.

Communication

Communication with the instrument is always initiated from the PC. Any string sent from the PC
should begin with the { character to start the synchronization. This should be followed by a 1­character product identification (see table below). The address is next (this is a 2-digit number
between 00 and 31 used to distinguish between the different instruments, probes, functions etc.
that are connected to the PC). The address is followed by a command and by any values or
parameters that may be required to carry out the command. Use a carriage return (CR) to
terminate the command string.

Example: {M03RDD} + CR (asks instrument M03 to send measurement data)

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When several instruments are connected together (RS485 network), commands directed to
instruments other than the instrument that is physically connected to the COM port of the PC
should be preceded with the | character (ASCII 124)

Example: |{U01RDD} + CR
The instrument answers with a string beginning with the { character, the product identification and

the address, followed by the command that was received and any data field that may have been
requested by the command. This is followed by a checksum.
The length of the string may vary, depending on how much data is included. Since the string itself
does not include any information about its own length, a carriage return (CR) is always used to
terminate the string.

Example: {M03RDD 0027.50;0023.76;0029.31;0022.77;#M (terminated with CR)
Note: Some instruments may insert the $ character at the second or third position of the string.

1-character Product Identification

ID Product Examples

(the instrument will answer the following command)

a A1H {a00M} + CR
d I3000, I3000S {d00zY + CR – assuming the address is 0
d BT-RS {d02z] + CR

w HygroWin Not Applicable

x MOK-Win {x00M} + CR
0 HygroPalm 1 Not Applicable
u HygroPalm 2 {u00RDD}+CR – assuming the address is 0

U HygroPalm 3 {U00RDD}+CR – assuming the address is 0

1 HygroFlex 1 Not Applicable
m HygroFlex 2 {m00RDD}+CR – assuming the address is 0
M HygroFlex 3 {M00RDD}+CR – assuming the address is 0

2 HygroLab 1 Not Applicable

b HygroLab 2 {b00RDD}+CR – assuming the address is 0

B HygroLab 3 {B00RDD}+CR – assuming the address is 0
X HygroLab 4 {X00RDD}+CR – assuming the address is 0

CR=Chr(13)

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Special Situations

Address 99 will cause any instrument to answer and, for this reason, should not be used when
several instruments are connected to a network. Address 99 can be useful when trying to
communicate with a single instrument of unknown address (the instrument address will be returned
as part of the answer).

When the product ID is unknown, it can be replaced with a blank in the command. The instrument
ID will be returned as part of the answer.

For information on specific commands, please contact ROTRONIC.