Michell Instruments Optidew User manual

Optidew & Optidew Vision
High Performance Optical
Dew-Point Transmitter
User’s Manual
97430 Issue 2
March 2017
Power On
Power Input
85-254 Vac47-440Hz
Communications Port
Status
Temperature
Probe
Output Connections
Dewpoint
Sensor
Warning:Disconnect power
supply before removing cover
OPTIDEW
High Performance Optical Dew-point Transmitter
Display Control
Alarm/Dcc
OPTIDEW VISION
Precision Dewpointmeter

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© 2016 Michell Instruments
This document is the property of Michell Instruments Ltd. and may not be copied or
otherwise reproduced, communicated in any way to third parties, nor stored in any Data
Processing System without the express written authorization of Michell Instruments Ltd.
Optidew & Optidew Vision
For Michell Instruments' contact information please go to
www.michell.com

Optidew Series User’s Manual
iv 97430 Issue 2, March 2017
Contents
Safety ................................................................................................................................vi
Electrical Safety ...........................................................................................................vi
Pressure Safety............................................................................................................vi
Toxic Materials .............................................................................................................vi
Repair and Maintenance ...............................................................................................vi
Calibration...................................................................................................................vi
Safety Conformity ........................................................................................................vi
Abbreviations.....................................................................................................................vii
Warnings ...........................................................................................................................vii
1 INTRODUCTION ................................................................................................1
1.1 Optidew Series ................................................................................................... 2
1.2 Optidew Sensor.................................................................................................. 3
2 INSTALLATION ..................................................................................................4
2.1 Mounting ........................................................................................................... 4
2.2 Instrument Connections...................................................................................... 4
2.2.1 Optidew Vision.............................................................................................. 6
2.3 Electrical Power Connections ............................................................................... 8
2.3.1 Analog Outputs............................................................................................. 9
2.3.2 Current Outputs............................................................................................ 9
2.3.3 Relay Outputs ............................................................................................. 10
2.4 Digital Communications Port.............................................................................. 10
2.5 Sensor Installation............................................................................................ 11
2.5.1 Integral Sensor Configuration....................................................................... 12
2.6 Remote Temperature Probe............................................................................... 12
3 OPERATION ...................................................................................................13
3.1 Display ............................................................................................................ 13
3.2 LOCAL and REMOTE modes............................................................................... 13
3.2.1 Screens ...................................................................................................... 14
3.3 Operational Functions ....................................................................................... 15
3.3.1 Operating Principle...................................................................................... 15
3.3.2 Operating Cycle .......................................................................................... 15
3.3.3 DCC ........................................................................................................... 16
3.3.4 DATA HOLD Phase ...................................................................................... 16
3.3.5 MAXCOOL................................................................................................... 17
3.3.6 FAST –Frost Assurance System Technology ................................................... 17
3.3.7 Mirror Condition and Peltier Power ............................................................... 18
3.4 Optisoft Application Software ............................................................................ 18
3.4.1 Virtual Hygrometer Window ......................................................................... 19
3.4.2 Mirror Condition .......................................................................................... 19
3.4.3 Instrument Status ....................................................................................... 20
3.4.4 Parameter Setup ......................................................................................... 21
3.4.5 Charting and Logging .................................................................................. 22
3.4.6 Statistics .................................................................................................... 23
3.4.7 Control Parameters ..................................................................................... 24
3.4.8 Calibration Correction .................................................................................. 24
3.4.9 Change of Password.................................................................................... 26
4 GOOD MEASUREMENT PRACTICE .....................................................................27
4.1 Sampling Hints ................................................................................................. 27

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Michell Instruments v
Figures
Figure 1 Optidew.....................................................................................................2
Figure 2 Optidew Vision ...........................................................................................2
Figure 3 Sample Block ...........................................................................................12
Figure 4 Operating Cycle........................................................................................15
Figure 5 Virtual Hygrometer Window ......................................................................19
Figure 6 Parameter Setup Window..........................................................................21
Figure 7 Chart/Log Control Panel Window ...............................................................22
Figure 8 Chart Window ..........................................................................................23
Figure 9 Basic Statistics Window.............................................................................23
Figure 10 Extracts from Calibration Certificates..........................................................24
Figure 11 Calibration Correction Window...................................................................26
Figure 12 Change Password Window ........................................................................26
Figure 13 Sensor Mirror Cleaning..............................................................................31
Appendices
Appendix A Technical Specification ............................................................................... 34
Appendix B Optidew RS232 Commands ........................................................................ 37
Appendix C Troubleshooting - Common Faults............................................................... 41
Appendix D Dimensional Drawings................................................................................47
D.1 Optidew ..................................................................................... 47
D.2 Optidew Integral Version.............................................................. 48
D.3 Optidew Vision ............................................................................ 49
D.4 Sensor and Probe Dimensions ......................................................50
Appendix E Quality, Recycling & Warranty Information................................................... 52
Appendix F Return Document & Decontamination Declaration........................................ 54
Tables
Table 1 Sensor Capabilities ......................................................................................3
Table 2 Sensor Body Materials .................................................................................3
5 MAINTENANCE ................................................................................................31
5.1 Sensor Mirror Cleaning...................................................................................... 31
5.2 Resetting the Mirror Condition ........................................................................... 31

Optidew Series User’s Manual
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Safety
The manufacturer has designed this equipment to be safe when operated using the procedures
detailed in this manual. The user must not use this equipment for any other purpose than that
stated. Do not apply values greater than the maximum value stated.
This manual contains operating and safety instructions, which must be followed to ensure the safe
operation and to maintain the equipment in a safe condition. The safety instructions are either
warnings or cautions issued to protect the user and the equipment from injury or damage. Use
qualified personnel and good engineering practice for all procedures in this manual.
Electrical Safety
The instrument is designed to be completely safe when used with options and accessories supplied
by the manufacturer for use with the instrument.
Pressure Safety
DO NOT permit pressures greater than the safe working pressure to be applied to the instrument.
The specified safe working pressure is 20 barg (300 psig). The pressure rated versions can withstand
250 barg (3600 psig).
Toxic Materials
The use of hazardous materials in the construction of this instrument has been minimized. During
normal operation it is not possible for the user to come into contact with any hazardous substance
which might be employed in the construction of the instrument. Care should, however, be exercised
during maintenance and the disposal of certain parts.
Repair and Maintenance
The instrument must be maintained either by the manufacturer or an accredited service agent. Refer
to www.michell.com for details of Michell Instruments’ worldwide offices contact information.
Calibration
The recommended calibration interval for the Optidew Series is one year, unless otherwise specified
by Michell Instruments. The instrument should be returned to the manufacturer, Michell Instruments,
or one of their accredited service agents for re-calibration. Refer to www.michell.com for details of
Michell Instruments’ worldwide offices contact information.
Safety Conformity
This product meets the essential protection requirements of the relevant EU directives.

Optidew Series User’s Manual
Michell Instruments vii
Abbreviations
The following abbreviations are used in this manual:
AC alternating current
aWwater activity - relative humidity on a scale of 0-1 with no units
atm pressure unit (atmosphere)
barg pressure unit (=100 kP or 0.987 atm) gauge
ºC degrees Celsius
ºF degrees Fahrenheit
(t – tdp) difference in ºC between ambient and dew-point temperature
DC direct current
FAST Frost Assurance System Technology
ft feet
gm-3 grams per cubic meter
gkg-1 grams per kilogram
IEC International Electrotechnical Commission
LED Light Emitting Diode
m meter(s)
mA milliampere
Max maximum
Min minimum
mm millimeters
m/sec meters per second
N/C not connected / normally closed relay contacts
N/O normally open relay contacts
Nl/min liters per minute
% percentage
psig pounds per square inch gauge
scfh standard cubic feet per hour
RS232 serial data transmission standard
RS485 serial data transmission standard
T temperature
V Volts
W Watts
Ohms
Warnings
The following general warnings listed below are applicable to this instrument. They are
repeated in the text in the appropriate locations.
Where this hazard warning symbol appears in the following
sections, it is used to indicate areas where potentially hazardous
operations need to be carried out.

Optidew Series User’s Manual
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INTRODUCTION
1 INTRODUCTION
The Optidew Series precision hygrometers are based on the proven, fundamental optical
dew-point measurement principle, giving long-term unmatched drift-free performance.
They offer a wide measurement range with a variety of sensor options to accommodate
almost any application.
Data Communication and Application Software
The Optidew Series provides two linear 4-20 mA outputs, and RS232 or RS485 serial
communications, allowing configuration and monitoring by a suitable computer, data
logger or other device. An adjustable volt-free contact alarm means that the Optidew
Series can be used for direct process control. The comprehensive application software
provides an interface to configure and control instrument functions, and enables all
measured and calculated parameters to be graphed or logged over time.
As a Calibration Reference
The Optidew Series make excellent entry level calibration references, supplied as
standard with a fully traceable in-house calibration or optional UKAS-certified calibration.
Their simple operation makes it possible for anyone to use with minimum training.
Simply connect the instrument, power it up and measurement will begin automatically.
Frost Assurance Technology (FAST)
Super-cooled water can exist at temperatures down to -30°C (-22°F), and when formed
on the mirror of a chilled mirror hygrometer can introduce errors of up to 10% in
reading. All Michell chilled mirror products feature FAST, the frost assurance technology
that guarantees all dew-point measurements below 0°C (+32°F) are made over ice. The
FAST system works by rapidly cooling the mirror until a film of ice has formed on the
mirror of pre-determined thickness – once ice has been formed, control returns to the
instrument and measurement can begin.
Compact and Convenient Package
The bench-top enclosure for the Optidew Vision has a handle that doubles as a stand.
An optional panel-mounting kit is also available for 19” rack mounting.
A bright and clear 2-line vacuum fluorescent display on the front panel enables the
instrument parameters to be monitored even when not connected to the application
software.

Optidew Series User’s Manual
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INTRODUCTION
1.1 Optidew Series
The Optidew Series is available in two variants, which differ only in enclosure type,
connectors and sensor cable:
Figure 1 Optidew
Figure 2
Optidew Vision
The Optidew features a rugged 304 stainless steel industrial enclosure, offering
protection to IP66 / NEMA 4x. The enclosure is suitable for wall mounting, and can be
ordered either as a blind transmitter or with an optional display.
The Optidew Vision is a bench top model, with integrated display, ideal for laboratory
use.

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INTRODUCTION
1.2 Optidew Sensor
Optidew Series’ sensors are available with either single stage, or dual stage peltier
devices, and with a variety of different sensor body and mirror materials. The following
tables show the capabilities of each sensor type:
Single Stage Dual Stage Dual Stage
Metal Body
Available sensor body materials Acetal Acetal
PEEK
Aluminum
Stainless steel
Approximate maximum depression 55°C (99°F) 65°C (117°F) 45°C (81°F)
Equivalent % RH range 2 to 100% 0.5 to 100% 4 to 100%
Lowest Measureable Dew Point
Sensor temperature 20°C (68°F) -30°C (-22°F) -40°C (-40°F) -20°C
With additional cooling -40°C (-40°F) -50°C (-58°F) N/A
Table 1 Sensor Capabilities
Acetal PEEK Stainless Steel
Aluminum
Maximum Temperature +90°C (+194°F) +130°C (+266°F)
Table 2 Sensor Body Materials
All sensor variants are available in high pressure versions, able to operate in pressure
up to 250 barg (3600 psig).

Optidew Series User’s Manual
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INTRODUCTION
2 INSTALLATION
2.1 Mounting
Optidew
The Optidew can be wall mounted using the four drilled tabs on each corner. It is
possible to install the Optidew outside, providing it is shielded from direct sunlight and
the climate is within the environmental requirements listed in Appendix A, Technical
Specifications.
An optional weatherproof connector kit is available for the analog and digital outputs
(Michell order code: OPT-WPS).
Optidew Vision
The Optidew Vision is designed to be bench mounted and is supplied with a tilting carry
handle, but it can also be panel mounted using the optional panel mounting kit (Michell
order code: OPV-PMK).
2.2 Instrument Connections
Optidew
Front Panel
1
OPTIDEW
High Performance Optical Dew-point Transmitter
h
2
h
Number Description
1Display (optional)
Shows measured or calculated instrument parameters. Refer to Section 3.1.
2
Display Control (with Display models only)
Switches between different display screens, and puts the instrument in
REMOTE MODE. Refer to Section 3.2.

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INSTALLATION
Bottom Panel
h h h
h
12 3 4
h
5
h
6
h
h
78
Number Description
1Power LED
Indicates that the Optidew is powered.
2
Status LED
Lit to indicate instrument is in DCC or DATA HOLD mode.
Flashes in the event of an Optics fault. This normally means the mirror
needs cleaning, followed by resetting the mirror condition during a DCC
cycle. Refer to Section 5 for more details.
3Serial Connector
For digital serial communications. Refer to Section 2.4.
4Sensor Connector
Used for connecting the Optidew sensor via the sensor cable.
5Mounting Point
For integral sensor version.
6Power Connector
Universal power input 90 to 264 V AC OR 127 to 370 V DC, 47 to 440 Hz
7Temperature Connector
For connection of remote PT100 temperature probe.
8Output Connector
Two current outputs, and two relay connections. Refer to Section 2.3.

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INSTALLATION
2.2.1 Optidew Vision
Front Panel
Display Control
Alarm/Dcc
O
PTIDEW
VISION
Pr
ecision Dewpointmeter
123
h
h
h
Number Description
1
Status LED
Lit to indicate instrument is in DCC or DATA HOLD mode.
Flashes in the event of an Optics fault. This normally means the mirror
needs cleaning, followed by resetting the mirror condition during a DCC
cycle. Refer to Section 5 for more details.
2Display
Shows measured or calculated instrument parameters. Refer to Section 3.1.
3
Display Control
Switches between different display screens, and puts the instrument in
REMOTE Mode. Refer to Section 3.2.

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INSTALLATION
Rear Panel
13
25
4
6
h
h
h
h
h
h
Number Description
1
Universal power input 90 to 264 V AC OR 127 to 370 V DC, 47 to 440 Hz
Features integrated ON/OFF switch, and fuse holder.
Fuse Type: 2A, Quick blow, Glass, 20 x 5mm
2Mirror Condition Potentiometer
Used to adjust mirror condition during a DCC cycle. Refer to Section 3.3.7.
3Serial Connector
For digital serial communications. Refer to Section 2.4.
4Temperature Connector
For connection of remote PT100 temperature probe.
5Sensor Connector
Used for connecting the Optidew sensor via the sensor cable.
6Output Connector
Two current outputs, and two relay connections. Refer to Section 2.3.

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INSTALLATION
2.3 Electrical Power Connections
WARNING:
The instrument must be GROUNDED.
The Optidew and Optidew Vision accept a power supply of the following specification:
Voltage 90 to 264 V AC OR 127 to 370 V DC
Frequency 47 to 440 Hz
Power Consumption 20 W max
Optidew
The Optidew is supplied as standard with a fully waterproofed power connector with a
2m (6.5ft) cable.
This power connector is wired as follows:
Pin Connection Conductor Color
Pin 1 Live (Line Voltage) Brown
Pin 2 N/C N/A
Pin 3 Neutral Blue
Ground Green & Yellow
NOTE: The Optidew is designed for continuous operation and therefore
does not feature a power on/off switch. As soon as power is applied, the
green power LED will illuminate and the transmitter will initiate a DCC cycle,
illuminating the system status LED.
The part number for a replacement power cable is OPT-POWER-CAB-2.
Optidew Vision
The Optidew Vision is supplied with a 2m (6.5ft) IEC cable. The IEC socket on the back
of the instrument features an integrated ON/OFF switch and fuse holder that accepts a
2A, Quick blow, Glass, 20 x 5mm fuse.

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INSTALLATION
2.3.1 Analog Outputs
The analog output connector is located on the front panel of the Optidew, and on the
rear panel of the Optidew Vision. The electrical connections are shown below:
Optidew
12345678
9101112131415
15-Way D Connector
Optidew Vision
123456789 10 11 12
12-Way Output Connector
Pin Description Pin Description
1 Channel 1 Current Output 1 Status Relay N/C
2 Channel 1 Ground 2 Status Relay COM
3 Channel 2 Current Output 3 Status Relay N/O
4 Channel 2 Ground 4 Optics Fault / Alarm Relay N/C
5-8 Not Connected 5 Optics Fault / Alarm Relay COM
9 Optics Fault / Alarm Relay N/O 6 Optics Fault / Alarm Relay N/O
10 Optics Fault / Alarm Relay COM 7 Channel 1 Current Output
11 Optics Fault / Alarm Relay N/C 8 Channel 1 Ground
12 Status Relay N/O 9 Channel 2 Current Output
13 Status Relay COM 10 Channel 2 Ground
14 Status Relay N/C 11-12 Screen
15 Not Connected
2.3.2 Current Outputs
Two current source outputs are provided which can be set to either 4-20 or 0-20 mA
and scaled by the user over the range –200 to +1000 by using the supplied application
software (see Section 3.4) or by sending the appropriate commands to the instrument
over RS232 or RS485 (see Appendix B).
Channel 1 can be set for dew point, %RH, gm-3, gkg-1 or delta (t-tdp).
Channel 2 always outputs temperature.
When the output is under-range, or over-range, the output signal will be 23mA.

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INSTALLATION
2.3.3 Relay Outputs
There are two sets of relay outputs available via the output connector:
• Alarm Relay
This relay changes state to indicate that the process variable has exceeded
the alarm set point value. The alarm set point value can be adjusted using the
supplied application software (see Section 3.4) or by sending the appropriate
commands to the instrument over RS232 or RS485 (see Appendix B).
• Status Relay
This relay changes state when the instrument is in DCC, DATA HOLD.
In the event of an optics fault, both relays will change state, and the status LED will
flash. This normally means the mirror needs cleaning, followed by resetting the mirror
condition during a DCC cycle. Refer to Section 5 for more details.
Refer to Section 2.3 for wiring details.
2.4 Digital Communications Port
The Optidew Series provides either RS232 or RS485 serial communications via a 9
way D-type connector. This allows for communication with a PC, data logger, or other
hardware device.
The following communication settings are required:
Baud Rate 9600
Data Bits 8
Stop Bit 1
Parity None
Pin No RS232 RS485
2TxB
3RxA
5 GND GND
For information on installing and using the supplied application software please refer to
Section 3.4.
For a list of serial commands please refer to Appendix B.
NOTE:ChangingbetweenRS232andRS485communicationrequireshardware
modifications and can only be carried out at the factory.
NOTE: Instruments with a display will only communicate when the display
shows REMOTE mode. (see Section 3.2).

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INSTALLATION
2.5 Sensor Installation
The dew-point sensor contains the optical system and the chilled mirror. It is fitted with
a bayonet connector to allow easy and secure connection to the instrument using the
supplied sensor cable.
The available options for sensor installation are:
• via a permanently installed sample port into which the remote sensor can
be inserted or
• via a sensor block immediately attached to the sensor around which the
sample circulates or
• in an ambient environment where the sample is diffusing through the
sensor.
If the instrument is to monitor the conditions in an environment, the sensor must be
located in a representative position, i.e. not under an air conditioning vent. NOTE: It is
recommended that the sensor is fitted with either an HDPE or stainless steel
sintered guard to baffle it from flowing air currents.
If the sensor is to be mounted directly into the process, tap a hole for fitment of the
widest thread (M36 x 1.5-6g), and seal using the Dowty washer provided.
1. Before connecting ensure that the sensor mirror surface is fully cleaned.
See Section 5 (Maintenance) for cleaning details.
2. If the sensor is installed within a sealed gas system it must be fixed
securely without any possibility of leaks. Ensure that the sample flow
across the sensor is correctly regulated.
3. The gas connections for the remote sensor are either via a permanently
installed sample port into which the remote sensor can be inserted or via
a sensor block (see
Figure 3) immediately attached to the sensor around
which the sample circulates. Gas sample entry into the sensor block is
via couplings that can be installed via ” NPT female threads. A Dowty
washer is provided to seal the connection between the sensor and the
block.
4. If the sensor is to be positioned into a sealed but open environment, e.g.
glove box, environmental chamber or area to be monitored, ensure that
the sensor is suitably secured to prevent any movement and that it is
located in a position that will see a representative flow of the sample to
be measured.
5. Connect the remote sensor cable to the sensor and to the instrument via
the connector on the rear panel. The connector is a 2-part bayonet fitting.
Insert the cable part and rotate until the polarization lugs engage. Rotate
the outer collar of the cable-mounted part in a clockwise direction, and, at
the same time, push the connector halves together to assist the mating.
The connection is made in a ¼ of a turn of the outside collar part.

Optidew Series User’s Manual
Michell Instruments 11
INSTALLATION
6. If the remote temperature probe is to be utilized, ensure that the probe
is suitably secured to prevent any movement and that it is located in a
position that will see a representative flow of the sample to be measured.
Gas Inlet (Ɨ” NPT)
Gas Outlet (Ɨ” NPT)
Sensor Connection
h
h
h
Figure 3 Sample Block
Michell Instruments can supply various sampling accessories including a locknut kit for
mounting the sensor in an ambient environment.
More complete sampling guidelines are available in Section 4.1.
2.5.1 Integral Sensor Configuration
The Optidew sensor can be fitted directly to the bayonet-type connector on the case of
the instrument without using a sensor cable. A retaining bracket provides support for
the sensor. NOTE: This is not possible with the Optidew Vision.
Installation / Removal
1. Connect the sensor to the bayonet-type connector on the case of the
Optidew.
2. Fit the retaining bracket (configuration drawing shown in Appendix D.1).
3. Secure the retaining bracket with the supplied locking nut.
4. Fit the optional sintered, or HDPE sensor guard, if required.
Follow the instructions in reverse to remove the sensor.
2.6 Remote Temperature Probe
The temperature probe is supplied pre-wired and simply needs to be fitted to the
connector on the Optidew or Optidew Vision prior to use.
The temperature probe can be safely disconnected or reconnected from the instrument
at any time.

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INSTALLATION
3 OPERATION
First Time Operation
Before using the instrument it is recommended to read through the Installation,
Operation and Maintenance Sections of this manual.
1. Clean the sensor mirror according to Section 5.1.
2. Install the sensor according to Section 2.5.
3. Set the flow to within 0.1 to 2Nl/min (optimal 0.5Nl/min).
4. After making all necessary electrical connections, power on the instrument.
5. During the DCC phase, reset the mirror condition according to Section
3.3.7.
6. If serial communication is required, and the instrument has a display it
must be placed in Remote Mode, see Section 3.2.
3.1 Display
The Optidew is available with an optional VFD (Vacuum Fluorescent Display) fitted on
the top panel of the instrument. The Optidew Vision features a front panel VFD. When
power is applied to the Optidew or Optidew Vision the display will momentarily show
test characters, after which the start-up banner will be displayed for approximately 7
seconds.
3.2 LOCAL and REMOTE modes
To the right of the display is a multi-function button.
Pressing the button in LOCAL mode scrolls through the available display screens.
Pressing and holding the button for 7 seconds toggles between LOCAL and REMOTE
mode.
NOTE: The display must have finished showing the start-up banner before
changing modes.
In LOCAL mode, RS232 or RS485 output is disabled and communication with a PC is
not possible. The measured and calculated parameters are shown on the display on a
number of different screens as shown in Section 3.2.1.
In REMOTE mode the display is inactive, and shows *REMOTE MODE*. The RS232 or
RS485 output is now enabled and available via the 9 pin communication D-connector.
This functionality is the same as the non-display version of the Optidew.