Michell Instruments Easidew User manual

Easidew
Dew-Point Transmitter
User’s Manual
97504 Issue 2
May 2018

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© 2018 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.
For Michell Instruments' contact information please go to
www.michell.com
Easidew

Easidew Transmitter User’s Manual
iv 97504 Issue 2, May 2018
Contents
Safety ....................................................................................................................................... v
Electrical Safety .................................................................................................................. v
Pressure Safety .................................................................................................................. v
Toxic Materials.................................................................................................................... v
Repair and Maintenance...................................................................................................... v
Calibration.......................................................................................................................... v
Safety Conformity ............................................................................................................... v
Abbreviations............................................................................................................................ vi
Warnings .................................................................................................................................. vi
1 INTRODUCTION .......................................................................................................... 1
2 INSTALLATION............................................................................................................. 2
2.1 Unpacking the Instrument......................................................................................... 2
2.2 Preparation of the Sensor Cable................................................................................. 3
2.3 Cable Connection...................................................................................................... 4
2.4 Electrical Schematic .................................................................................................. 5
2.4.1 Electrical Boundaries ........................................................................................... 6
2.4.2 Digital Communication (M12 Version only) ............................................................ 6
2.5 Transmitter Installation ............................................................................................. 6
2.5.1 Sampling Considerations...................................................................................... 6
2.5.2 Sampling Hints ................................................................................................... 8
2.5.3 Transmitter Mounting ........................................................................................ 11
2.5.3.1 5/8” 18 UNF Version ................................................................................... 11
2.5.3.2 3/4” - 16 UNF Version ................................................................................. 12
2.5.3.3 G1/2" BSPP Version .................................................................................... 12
2.5.3.4 Installation using Additional Thread Adaptor................................................. 12
3 MAINTENANCE .......................................................................................................... 14
Figures
Figure 1 DIN43650 Transmitter Unpacking Method ......................................................... 2
Figure 2 Connector Terminal Block Removal ................................................................... 3
Figure 3 Wiring Connections ......................................................................................... 3
Figure 4 Connector Installation...................................................................................... 4
Figure 5 Connector Installation...................................................................................... 5
Figure 6 2-Wire Connection Diagram ............................................................................. 5
Figure 7 Maximum Load of Easidew - Including Cable Resistance .................................... 6
Figure 8 Installation Location ........................................................................................ 7
Figure 9 Transmitter Mounting - Sensor Block................................................................. 8
Figure 10 Material Permeability Comparison ..................................................................... 9
Figure 11 Dead volume ................................................................................................ 10
Figure 12 Transmitter Mounting - Pipe or Duct ............................................................... 11
Figure 13 Transmitter Mounting with Adapter ................................................................ 13
Figure 14 Replacement of HDPE Guard.......................................................................... 14
Figure 15 Dimensions - Easidew ................................................................................... 17
Appendices
Appendix A Technical Specifications ...................................................................................16
Appendix B Quality, Recycling & Warranty Information ........................................................19
Appendix C Return Document & Decontamination Declaration..............................................21

Easidew Transmitter User’s Manual
Michell Instruments v
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
competent personnel using 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 45 MPa (450 barg / 6500 psig). Refer to the Technical
Specifications in Appendix A.
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. For
Michell Instruments’ contact information please go to www.michell.com.
Calibration
The recommended calibration interval for this instrument is 12 months unless it is to be used in a
mission-critical application or in a dirty or contaminated environment in which case the calibration
interval should be reduced accordingly. The instrument should be returned to the manufacturer,
Michell Instruments Ltd., or one of their accredited service agents for re-calibration.
Safety Conformity
This product meets the essential protection requirements of the relevant EU and US standards
and directives. Further details of applied standards may be found in the Technical Specifications in
Appendix A.

Easidew Transmitter User’s Manual
vi 97504 Issue 2, May 2018
Abbreviations
The following abbreviations are used in this manual:
barg pressure unit (=100 kP or 0.987 atm) gauge
ºC degrees Celsius
ºF degrees Fahrenheit
DC direct current
ft-lbs foot-pound force
g grams
in inch(es)
m micrometer
m/sec meters per second
mA milliampere
max maximum
mm millimetres
MPa megapascal
Nl/min normal liters per minute
Nm Newton meter
oz ounces
ppmV parts per million by volume
psig pounds per square inch
RH relative humidity
scfh standard cubic feet per hour
scfs standard cubic feet per second
T temperature
V Volts
Ohms
ø diameter
Warnings
The following general warning listed below is applicable to this instrument. It is 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.

Easidew Transmitter User’s Manual
Michell Instruments 1
INTRODUCTION
1 INTRODUCTION
The Michell Instruments Easidew is a 4-20mA loop-powered dew-point transmitter,
designed to make dew point measurements in a flowing sample. The Easidew transmitter
is available with 3 different process connections:
• 5/8" - 18 UNF : Easidew 2-wire, Easidew M12
• 3/4" - 16 UNF : Easidew 34, Easidew M12
• G1/2 : Easidew M12
The Easidew 2-wire is available with a choice of electrical connections:
• DIN 43650 Form C
• M12 5-Pin

Easidew Transmitter User’s Manual
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INSTALLATION
2 INSTALLATION
2.1 Unpacking the Instrument
On delivery, please check that all the following standard components are in the packing
tube:
• Easidew Transmitter
• Certificate of Calibration
• Connector (for sensor/cable)
The Transmitter will also be supplied with a process seal, which will be fitted to the
unit. Depending on the version, this will either be a bonded seal (5/8" or G1/2" thread
versions) or an o-ring seal (3/4" thread versions).
Unpack the dew-point transmitter tube as follows:
87653 421
Figure 1
DIN43650 Transmitter Unpacking Method
1. Unscrew the cap (1) from the packing tube (8).
2. Remove the foam block (3) containing the connector (2).
3. Pull out the transmitter (5) from the tube, complete with the two foam
covers (6) and (7) and the red protective cap (4).
4. Remove the foam covers from the transmitter but leave the blue plastic
protective cover (5) and the red cap (4) in place until ready for installation.
NOTE: The transmitter sensing element is protected while in transit by a blue
cover containing a small desiccant capsule. The connection pins are protected
by a red plastic cap. None of these plastic items are required for the operation
of the transmitter.
NOTE: Keep the connector (2) in a safe place until the transmitter is ready
for wiring.

Easidew Transmitter User’s Manual
Michell Instruments 3
INSTALLATION
2.2 Preparation of the Sensor Cable
The sensor cable is NOT supplied as standard. Cables can be obtained by contacting your
local Michell Instruments representative (see www.michell.com for details).
DIN 43650 Version
Cable connection to the Easidew transmitter is made via the removable connector. Removing
the central screw enables the connector terminal block to be removed from the outer
housing by using a small screwdriver to prise it clear.
i
O-ring
and washer
Figure 2 Connector Terminal Block Removal
Caution: When removing the central screw ensure that the
small sealing O-ring and the washer are retained on the screw
and are present during re-installation.
The sensor cables are terminated as per the following diagram:
SCALE 2:1
i
j
SHORT
AS POSSIBLE
h
1
3
24
BLUE
BRAID BRAID
GREEN 4-20 mA
(SOURCE)
SCREEN
RED
+POWER
GND
VIEW ON REAR
OF CONNECTOR
GREEN
SIGNAL (SOURCE) GREEN
YELLOW
BLUE
RED
h
h
BLUE - GND / SCREEN
RED + POWER
GREEN 4-20 mA
BLUE - GND / SCREEN
RED + POWER
GN
RD
BL
Figure 3 Wiring Connections
Note: The screen should only be connected to a ground point at either the
transmitter installation side, or at the receiving equipment. Failure to observe
this precaution can result in ground loops and equipment malfunction.

Easidew Transmitter User’s Manual
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INSTALLATION
.
Always connect the 4-20 mA return signal to a suitable load
(see Figure 3) before the power is applied. Without this
connection, the transmitter may be damaged if allowed to
operate for prolonged periods.
M12 5-Pin Version
Cables with moulded M12 connectors are available from Michell Instruments in the
following lengths:
• 0.8m
• 2m
• 5m
4-20 mA 2-wire
PIN 1 Modbus B
PIN 2 Modbus A
PIN 3 4-20 mA
PIN 4 Power supply
PIN 5 0V
Figure 4 Sensor Connector Installation
The other end of the sensor cable is unterminated, for straightforward connection into
the desired monitoring system.
CABLE ASSEMBLY CONNECTIONS
FUNCTION PIN WIRE COLOUR
MODBUS B 1 BROWN
MODBUS A 2 WHITE
4 - 20 mA 3 BLUE
POWER SUPPLY 4 BLACK
Ov 5 GREY
If longer cable runs are required, off-the-shelf 5-pin M12 cables can be connected
between the Easidew transmitter and the cable provided by Michell Instruments.
Note: The screen should only be connected to a ground point at either the
transmitter installation side, or at the receiving equipment. Failure to observe
Figure 5 Cable connections

Easidew Transmitter User’s Manual
Michell Instruments 5
INSTALLATION
this precaution can result in ground loops and equipment malfunction.
2.3 Cable Connection
DIN 43650 Version
To ensure the specified ingress protection is achieved, when installing the connector, the
securing screw (with the O-ring and washer) must be tightened to a minimum torque of 3.4
Nm (2.5 ft-lbs). The sensor cable used must be a minimum diameter of 4.6mm (0.2”).
O-ring
and washer
i
Figure 6 Connector Installation
M12 5-Pin Version
The connector should be installed by aligning the locating pin on the transmitter with
the slot on the cable. The connector can then be pushed into place and rotated until
finger-tight.
2.4 Electrical Schematic
Note: The screen should only be connected to a ground point at either the
transmitter installation side, or at the receiving equipment. Failure to observe
this precaution can result in ground loops and equipment malfunction.
3
1
Max Load
200R @ 12V
500R @ 24V
Supply
12V Min
28V Max
+
Screen/
Shield
Figure 7 2-Wire Connection Diagram

Easidew Transmitter User’s Manual
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INSTALLATION
2.4.1 Electrical Boundaries
100
200
300
400
500
600
12 14 16 18 20 22 24 26 28
Resistance (ohms)
Supply Voltage
Figure 8
Maximum Load of Easidew - Including Cable Resistance
2.4.2 Digital Communication (M12 Version only)
Modbus RTU over RS485 communication is available on the Easidew M12, and can be
used simultaneously with the 2-wire current output. Section 2.2 describes the electrical
connections to the transmitter.
The Modbus register map can be found at the end of this manual.
2.5 Transmitter Installation
2.5.1 Sampling Considerations
There are two basic methods of measuring a sample with the Easidew Transmitter:
In-situ measurements are made by placing the transmitter inside the environment to
be measured.
Extractive measurements are made by installing the sensor into a block within a sample
handling system, and flowing the sample outside of the environment to be measured
through this system.
Extractive measurements are recommended when the conditions in the environment
to be measured are not conducive to making reliable measurements with the product.

Easidew Transmitter User’s Manual
Michell Instruments 7
INSTALLATION
Examples of such conditional limitations are:
• Excessive flow rate
• Presence of particulates matter
• Presence of entrained liquids
• Excessive sample temperature
The basic considerations for each measurement type are as follows:
In-Situ
1. Dew-Point Sensor Position – will the sensor see an area of the
environment that is representative of what you want to measure?
For example, if the sensor is to be mounted into a glove box, there are three different
positions in which it could be installed – each giving a different measurement:
• Position A is on the purge inlet. In this position the sensor will confirm the
dew point of the gas entering the glove box, but will not detect any leaks
in the glove box itself, or any moisture released from the work piece.
• Position B is on the gas outlet. In this position the sensor will be exposed
to the gas leaving the glove box, and will therefore be detecting any
moisture which has entered into the system (e.g. ingress/leaks), or has
been released by the work piece.
• Position C is in the glovebox itself, in this position the sensor will be
only detecting any moisture in its immediate vicinity. Leaks not in close
proximity to the measurement point may not be detected as this moisture
could be drawn directly to the outlet.
B
C
A12
1. Purge Inlet
2. Gas Outlet
Figure 9 Installation Location
If the transmitter is to be mounted directly into a pipe or duct, then consider that the
installation point should not be too close to the bottom of a bend where oil or other
condensate may collect.

Easidew Transmitter User’s Manual
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INSTALLATION


Figure 10 Installation Location
2. Gas speed – if you are planning on installing the sensor in a duct, consider
how fast the sample gas is moving through it.
If the gas speed is very low, or occasionally static, then the moisture content through
the length (and width, if it is more than a few cm across) of the duct is unlikely to be
uniform.
Extremely high gas speeds can cause damage to the sensor. Direct insertion is not
recommended in gas speeds in excess of 10m/s (32.8ft/s).
3. Particulates – Particulates travelling at speed can cause severe and
irreversible damage to the sensor. At low velocity they can cling to the sensor,
reducing its’ surface area, and therefore response speed.
The sensor is provided with a basic level of particulate protection in the form of a
sintered guard; either HDPE (10m pore size) or Stainless Steel (80m pore size). If
the sample stream contains smaller particulates than this, or generally large amounts
of dust; extractive measurement is recommended to accommodate proper in-line
filtration.
4. Sample Temperature – Although the Easidew can be operated at sample
temperatures up to 70°C, it is advisable to keep the sample temperature as
close to ambient, and as stable as possible to keep adsorption & desorption
characteristics as consistent as possible (see section X.X Sampling Hints for
more information).
Extractive
If the sensor is to be mounted into a sample conditioning system, then the above points are
still of relevance, but it is important to consider the extraction point itself – make sure that
the chosen extraction point is representative of the process, i.e. that the sample of interest
is flowing past the extraction point, and it is not being pulled from a dead volume.

Easidew Transmitter User’s Manual
Michell Instruments 9
OPERATION
1
2
3
2a 4
Figure 11 Transmitter Mounting - Sensor Block
2.5.2 Sampling Hints
Measurement of moisture content is a complex subject, but does not need to be difficult.
This section aims to explain the common mistakes made in measurement situations, the
causes of the problem, and how to avoid them. Mistakes and bad practices can cause the
measurement to vary from the expectation; therefore a good sampling technique is crucial
for accurate and reliable results.
Figure 12
Material Permeability Comparison
All materials are permeable to water vapour, as the water molecule is extremely small
compared to the structure of solids, even when compared to the crystalline structure of
metals. The graph above shows the dew point inside tubing of different materials when
purged with very dry gas, where the exterior of the tubing is in the ambient environment.
Many materials contain moisture as part of their structure, particularly organic materials
(natural or synthetic), salts (or anything which contains them) and anything which
has small pores. It is important to ensure that the materials used are suitable for the
application.
If the partial water vapour pressure exerted on the outside of a compressed air line is
higher than on the inside, the atmospheric water vapour will naturally push through the

Easidew Transmitter User’s Manual
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OPERATION
porous medium causing water to migrate into the pressurised air line. This effect is called
transpiration.
Adsorption and Desorption
Adsorption is the adhesion of atoms, ions, or molecules from a gas, liquid, or dissolved
solid to the surface of a material, creating a film. The rate of adsorption is increased at
higher pressures and lower temperatures.
Desorption is the release of a substance from or through the surface of a material.
In constant environmental conditions, an adsorbed substance will remain on a surface
almost indefinitely. However, as the temperature rises, so does the likelihood of desorption
occurring.
In practical terms, as the temperature of the environment fluctuates, water molecules are
adsorbed and desorbed from the internal surfaces of the sample tubing, causing small
fluctuations in the measured dew point.
Sample Tubing Length
The sample point should always be as close to the critical measurement point as possible,
in order to obtain a truly representative measurement. The length of the sample line
to the sensor or instrument should be as short as possible. Interconnection points and
valves trap moisture, so using the simplest sampling arrangement possible will reduce the
time it takes for the sample system to dry out when purged with dry gas.
Over a long tubing run, water will inevitably migrate into any line, and the effects
of adsorption and desorption will become more apparent. It is clear from the graph
shown above that the best materials to resist transpiration are stainless steel and
PTFE.
Trapped Moisture
Dead volumes (areas which are not in a direct flow path) in sample lines, hold
onto water molecules which are slowly released into the passing gas; this results in
increased purge and response times, and wetter than expected readings. Hygroscopic
materials in filters, valves (e.g. rubber from pressure regulators) or any other parts of
the system can also trap moisture.
Figure 13
Dead volume
Sample Conditioning
Sample conditioning is often necessary to avoid exposure of sensitive measuring
components to liquids and other contaminants which may cause damage or
affect the accuracy over time, depending on the measurement technology.
Particulate filters are used for removing dirt, rust, scale and
any other solids that may be in a sample stream. For protection
against liquids, a coalescing filter should be used.

Easidew Transmitter User’s Manual
Michell Instruments 11
OPERATION
The membrane filter is a more expensive but highly effective alternative to a
coalescing filter. It provides protection from liquid droplets, and can even stop
flow to the analyser completely when a large slug of liquid is encountered.
Condensation and Leaks
Maintaining the temperature of the sample system tubing above the dew
point of the sample is vital to prevent condensation. Any condensation
invalidates the sampling process as it changes the water vapour content of
the gas being measured. Condensed liquid can alter the humidity elsewhere
by dripping or running to other locations where it may re-evaporate.
The integrity of all connections is also an important consideration, especially
when sampling low dew points at an elevated pressure. If a small leak occurs in a
high pressure line, gas will leak out but vortices at the leak point and a negative
vapour pressure differential will also allow water vapour to contaminate the flow.
Flow Rates
Theoretically flow rate has no direct effect on the measured moisture
content, but in practice it can have unanticipated effects on response speed
and accuracy. The optimal flow rate varies depending on the measurement
technology, and can always be found in the instrument or sensor manual.
An inadequate flow rate can:
• Accentuate adsorption and desorption effects on the gas passing through the
sampling system.
• Allow pockets of wet gas to remain undisturbed in a complex sampling
system, which will then gradually be released into the sample flow.
• Increase the chance of contamination from back diffusion: ambient air that
is wetter than the sample can flow from the exhaust back into the system.
A longer exhaust (sometimes called a pigtail) can also help alleviate this
problem.
• Slow the response of the sensor to changes in moisture content.
2.5.3 Transmitter Mounting
Once an installation location has been chosen, this point will require a thread to match
the transmitter thread. Fixing dimensions are shown in Figure 6. For circular pipework,
to ensure the integrity of a gas tight seal, a mounting flange will be required on the
pipework in order to provide a flat surface to seal against.

Easidew Transmitter User’s Manual
12 97504 Issue 2, May 2018
MAINTENANCE
1
2
3
48mm
1
2
3
Figure 14 Transmitter Mounting - Pipe or Duct
2.5.3.1 5/8” 18 UNF Version
1. Remove the protective cover and desiccant capsule from the transmitter and
retain for future use
2. Prevent any contamination of the sensor before installation by handling the
transmitter by the main body only, avoiding contact with the sensor guard.
3. Pass the bonded seal over the 5/8”- 18 UNF mounting thread.
4. Screw the transmitter into the sampling location or sample block by hand
using the wrench flats only. DO NOT grip and twist the sensor cover
when installing the sensor.
5. When installed, fully tighten using a wrench to a torque setting of 30.5 Nm
(22.5 ft-lbs)

Easidew Transmitter User’s Manual
Michell Instruments 13
APPENDIX A
2.5.3.2 3/4” - 16 UNF Version
1. Remove the protective cover and desiccant capsule from the transmitter and
retain for future use.
2. Prevent any contamination of the sensor before installation by handling the
transmitter by the main body only, avoiding contact with the sensor guard.
3. Ensure that the O-ring is seated in the recess at the top of the transmitter
body.
4. Screw the transmitter into the sampling location or sample block by hand
using the wrench flats only. DO NOT grip and twist the sensor cover
when installing the sensor.
5. When installed, fully tighten using a wrench to a torque setting of 40 Nm
(29.5 ft-lbs).
2.5.3.3 G1/2" BSPP Version
1. Remove the protective cover and desiccant capsule from the transmitter
and retain for future use
2. Prevent any contamination of the sensor before installation by handling
the transmitter by the main body only, avoiding contact with the sensor
guard.
3. Pass the bonded seal over the G1/2" mounting thread.
4. Screw the transmitter into the sampling location or sample block by hand
using the wrench flats only. DO NOT grip and twist the sensor cover
when installing the sensor.
5. When installed, fully tighten using a wrench to a torque setting of 30.5
Nm (22.5 ft-lbs)
2.5.3.4 Installation using Additional Thread Adaptor
1. Remove the protective cover and desiccant capsule from the transmitter and
retain for future use
2. Prevent any contamination of the sensor before installation by handling the
transmitter by the main body only, avoiding contact with the sensor guard.
3. Pass the bonded seal over the 5/8”- 18 UNF mounting thread.
4. Screw the transmitter into the adaptor, and tighten to 30.5 Nm (22.5 ft-lbs)
5. NOTE: Use the flats of the hexagonal nut and not the sensor body.
6. Screw the transmitter (1) with its seal (3) and adapter (4) into the sampling
location block (and fully tighten using a wrench to the following torque settings:
• G 1/2” BSP 56 Nm (41.3 ft-lbs)
• 3/4” - 16 UNF ` 40 Nm (29.5 ft-lbs)
• 1/2” NPT Use a suitable sealant e.g. PTFE tape using correct taping
procedures

Easidew Transmitter User’s Manual
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OPERATION
1
2
34
2a
Figure 15 Transmitter Mounting with Adapter
MAINTENANCE
Calibration
Annual recalibration of the Easidew is recommended to maintain the performance.
Calibration services traceable to the UK National Physical Laboratory (NPL) and the
US National Institute of Standards and Technology (NIST) are provided by Michell
Instruments.
Michell Instruments offers a variety of re-calibration and exchange sensor schemes to
suit specific needs. A Michell representative can provide detailed, custom advice (for
Michell Instruments’ contact information go to www.michell.com).
Sensor Guard Replacement
The sensor is supplied with a white HDPE guard (standard) or a stainless steel guard (if
specified at time or order).
The sensor guard should be replaced if the surface shows any damage or signs of
discolouration. When replacing a guard, make sure to wear clkean disposable gloves,
and handle by the threaded base section only.
Replacement HDPE or stainless steel guards can be ordered from your Michell Instruments
representative.
t
e
r
0
9
0
6
M
I
C
H
E
I
n
s
t
r
u
m
e
n
x
HANDLE,
USING
GLOVES, BY
BLACK PART
ONLY
Figure 16 Replacement of HDPE Guard
Bonded Seal
If the supplied bonded seal is damaged or lost, a pack of 5 replacement bonded seals