Page 1
SF82
Dew-Point Transmitter
User Manual
97576 Issue 1.2
March 2022
Page 2
Please ll out the form(s) below for each instrument that has been purchased.
Use this information when contacting Michell Instruments for service purposes.
Product Name
Order Code
Serial Number
Invoice Date
Installation Location
Tag Number
Product Name
Order Code
Serial Number
Invoice Date
Installation Location
Tag Number
Product Name
Order Code
Serial Number
Invoice Date
Installation Location
Tag Number
Page 3
SF82
For Michell Instruments' contact information please go to
www.michell.com
© 2022 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.
Page 4
SF82 Transmitter User Manual
Contents
Safety ...............................................................................................................................vii
Electrical Safety..................................................................................................................vii
Pressure Safety .................................................................................................................. vii
Toxic Materials ...................................................................................................................vii
Repair and Maintenance ..................................................................................................... vii
Safety Conformity ..............................................................................................................vii
Abbreviations .................................................................................................................... viii
Warnings .......................................................................................................................... viii
1 INTRODUCTION ................................................................................................1
2 INSTALLATION ..................................................................................................2
2.1 Unpacking the SF82 Transmitter .......................................................................... 2
2.2 SF82 Transmitter ................................................................................................ 3
2.2.1 SF82 DIN 43650 Connector Version ................................................................ 3
2.2.1.1 Electrical Connections .............................................................................. 4
2.2.1.2 Cable Connection to Transmitter ............................................................... 4
2.2.1.3 Sensor Cable Self-Assembly ..................................................................... 5
2.2.2 SF82 M12 Connector Version ......................................................................... 6
2.2.2.1 Electrical Connections .............................................................................. 6
2.2.2.2 SF82 M12 Cables .................................................................................... 7
2.2.3 4...20 mA wiring schematics .......................................................................... 7
2.2.4 RS485 / Modbus RTU communication & wiring schematics ............................... 8
2.2.5 Cable Selection for Self-Assembled Cables ....................................................... 9
2.2.6 Maximum Loop Resistance vs Supply Voltage .................................................. 9
2.3 Transmitter Mounting ........................................................................................ 10
2.3.1 5/8” 18 UNF Version .................................................................................... 10
2.3.2 3/4” - 16 UNF Version ................................................................................. 10
2.3.3 G1/2” BSPP Version ..................................................................................... 10
2.3.4 Transmitter Mounting – Sample Block (Optional) ........................................... 11
2.3.4.1 Sample Block Gas Connections ............................................................... 11
2.3.4.2 Sensor Installation ................................................................................ 12
2.3.5 Transmitter Mounting – Direct Pipeline Connection ........................................ 13
2.3.6 Transmitter Mounting – With Additional Process Connection Adapter .............. 14
3 MAINTENANCE ................................................................................................15
3.1 Maintenance and Calibration ............................................................................ 15
4 MEASUREMENT GUIDE ....................................................................................17
4.1.1 Sampling Considerations .............................................................................. 17
4.1.2 Sampling Hints............................................................................................ 20
iv 97576 Issue 1.2, March 2022
Page 5
SF82 Transmitter User Manual
Figures
Figure 1 Transmitter Unpacking Method ....................................................................2
Figure 2 SF82 Transmitter ........................................................................................3
Figure 3 Connector Installation .................................................................................4
Figure 4 Connector Terminal Block Removal ..............................................................5
Figure 5 Cable Assembly ..........................................................................................5
Figure 6 Sensor Connector Installation ......................................................................6
Figure 7 Maximum Load of SF82 – Including Cable Resistance ....................................9
Figure 8 Sample Block Gas Connections ..................................................................11
Figure 9 Transmitter Mounting – Sensor Block .........................................................12
Figure 10 Transmitter Mounting – Pipe or Duct ..........................................................13
Figure 11 Transmitter Mounting with Adapter ...........................................................14
Figure 12 Replacement of HMWPE Guard ..................................................................15
Figure 13 Installation Location .................................................................................18
Figure 14 Installation Location .................................................................................18
Figure 15 Material Permeability Comparison ..............................................................20
Figure 16 Dead volume ............................................................................................21
Michell Instruments v
Page 6
SF82 Transmitter User Manual
Appendices
Appendix A Technical Specications ..............................................................................25
A.1 Dimensions .................................................................................26
Appendix B Modbus Register Map ................................................................................30
Appendix C Quality, Recycling & Warranty Information ................................................... 34
Appendix D Return Document & Decontamination Declaration ........................................ 36
vi 97576 Issue 1.2, March 2022
Page 7
SF82 Transmitter User Manual
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
This instrument is designed to be electrically safe when used with the options and accessories
supplied by Michell Instruments for use with it. This instrument has been independently veried as
complying with the IEC/EN 61010 Standard for Electrical Safety for Europe and for the equivalent
61010 standards in use in N. America. The instrument is approved for use within the operating
temperature range of -40°C to +60°C (-40°F to +140°F), and dependent on version, as being
IP66/65. See Specication section for full details.
Pressure Safety
DO NOT permit pressures greater than the safe working pressure to be applied to the instrument.
The specied safe working pressure is 45 MPag (450 barg / 6500 psig). Refer to the Technical
Specications 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, UK and US standards
and directives.
Michell Instruments vii
Page 8
Abbreviations
The following abbreviations are used in this manual:
barg pressure unit (=100 kP or 0.987 atm) (bar gauge)
ºC degrees Celsius
ºF degrees Fahrenheit
DC direct current
g grams
in inch(es)
µm micrometer
m/sec meters per second
mA milliampere
mm millimetres
MPa megapascal
Nl/min normal liters per minute
Nm Newton meter
oz ounces
psig pounds per square inch
RH relative humidity
scfh standard cubic feet per hour
fps feet per second
T temperature
V Volts
Ω Ohms
ø diameter
SF82 Transmitter User Manual
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.
viii 97576 Issue 1.2, March 2022
Page 9
SF82 Transmitter User Manual
1 INTRODUCTION
The Michell Instruments SF82 is a loop-powered dew-point transmitter, designed to
make dew point measurements in a flowing sample. The SF82 transmitter is available
with 3 different process connections:
• 5/8” – 18 UNF
• 3/4” – 16 UNF
• G1/2” – BSPP
The SF82 2-wire is available with a choice of electrical connections:
• DIN 43650 Form C
• M12 5-pin
INTRODUCTION
Michell Instruments 1
Page 10
INSTALLATION
7653 421
2 INSTALLATION
2.1 Unpacking the SF82 Transmitter
NOTE: For environmental and operating conditions refer to Appendix A.
SF82 Transmitter User Manual
Unpack the dew-point transmitter box as follows
Figure 1
1. Unscrew the cap (1) from the packing tube (7). Remove the foam block
(2).
2. Remove the transmitter from the tube, complete with the body cover (5)
and tip cover (6).
3. Remove the body cover (5) and the tip cover (6) but leave the blue plastic
protective cover (4) in place until ready for installation.
NOTE: The transmitter sensing element is protected while in transit by a blue,
green or black 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.
Transmitter Unpacking Method
:
2 97576 Issue 1.2, March 2022
Page 11
SF82 Transmitter User Manual
2.2 SF82 Transmitter
NOTE: The transmitter’s sensing element is shown for illustration purposes
only. Please keep the guard fitted at all times, if possible.
INSTALLATION
Figure 2
2.2.1 SF82 DIN 43650 Connector Version
The following sections apply only to the DIN 43650 connector version of the transmitter.
SF82 Transmitter
Michell Instruments 3
Page 12
INSTALLATION
2.2.1.1 Electrical Connections
SF82 Transmitter User Manual
Connector
Pin
1 Green 4...20 mA Signal Return (Power Supply -ve)
3 Red Power Supply +ve
GND Blue Ground, Cable Screen Connection
Warning: The sensor must be operated with the 4...20 mA signal return connected to
a suitable load, or negative power supply connection. Leaving this pin unconnected may
result in damage to the transmitter. Refer to wiring schematics later on in this document
for connection examples.
NOTE: The sensor cable is NOT supplied as standard. Replacement pre-wired cables can
be obtained by contacting your local Michell Instruments representative or assembled
by the user according to instructions in the following section.
Michell Standard
Conductor Color
Function
This pin directly connects to the metal casing
of the transmitter, but not to the transmitter
electronics, and is intended for cable screening
only.
2.2.1.2 Cable Connection to Transmitter
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
4.6 mm (0.2”).
Figure 3
Connector Installation
4 97576 Issue 1.2, March 2022
Page 13
SF82 Transmitter User Manual
2.2.1.3 Sensor Cable Self-Assembly
For guidance on type of cable refer to Section 2.2.5, Cable Selection for Self-Assembled
Cables.
Assembly Instructions
1. Remove the screw from the rear of the DIN connector housing.
2. Lever the terminal block from the connector housing by inserting a small
screwdriver in the notch on the front face of the terminal block.
3. Ensure the small sealing O-ring and washer and retained with the screw.
INSTALLATION
Figure 4
4. Cable should be assembled according to
Connector Terminal Block Removal
Figure 5
Cable Assembly
Figure 5
.
Michell Instruments 5
Page 14
INSTALLATION
2.2.2 SF82 M12 Connector Version
The following sections apply only to the M12 connector version of the transmitter.
2.2.2.1 Electrical Connections
SF82 Transmitter User Manual
Figure 6
Connector
Pin
1 Brown Modbus A
2 White Modbus B
3 Blue 4...20 mA Signal Return (Power Supply -ve)
4 Black Power Supply +ve
5 Grey Ground, Cable Screen Connection
Warning: The sensor must be operated with the 4...20 mA signal return connected to
a suitable load, or negative power supply connection. Leaving this pin unconnected may
result in damage to the transmitter. Refer to wiring schematics later on in this document
for connection examples.
NOTE: The sensor cable is NOT supplied as standard. Replacement pre-wired cables can
be obtained by contacting your local Michell Instruments representative or assembled
by the user according to instructions in the following section.
Michell Standard
Conductor Color
Sensor Connector Installation
Function
This pin directly connects to the metal casing of the
transmitter, but not to the transmitter electronics,
and is intended for cable screening only.
6 97576 Issue 1.2, March 2022
Page 15
SF82 Transmitter User Manual
2.2.2.2 SF82 M12 Cables
The cable 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.
Cables with moulded M12 connectors are available from Michell Instruments in the
following lengths:
• 0.8 m
• 2 m
• 5 m
• 10 m
The other end of the sensor cable is unterminated, for straightforward connection into
the desired monitoring system.
If longer cable runs are required, off-the-shelf 5-pin M12 cables can be connected
between the SF82 transmitter and the cable provided by Michell Instruments.
INSTALLATION
2.2.3 4...20 mA wiring schematics
Example 1: Connecting the transmitter using an external power supply to provide the
excitation voltage
+24 V
Power Supply
0 V
Current Measurement Device
Monitor/PLC/DCS etc.
Example 2: Connecting the transmitter to a device that provides its own excitation
voltage
Power
Supply +ve
Moisture
Transmitter
4...20 mA
Signal Return
+ve−ve
Power
+24 V
Supply +ve
Moisture
Monitor
Transmitter
4...20 mA
Signal Return Input
Michell Instruments 7
4...20 mA
Signal Return
Page 16
INSTALLATION
2.2.4 RS485 / Modbus RTU communication & wiring schematics
The M12 version of the transmitter should be used if
continuous monitoring or measurement via the RS485 /
Modbus interface is required. The RS485 interface on the
DIN version is intended for conguration and diagnostics
and should only be used with a Michell Instruments
communications kit. Incorrect wiring of the transmitter may
result in permanent damage.
Modbus RTU over RS485 communication is available on the SF82 M12 and can be used
simultaneously with the 2-wire current output.
Full details of the Modbus communications is contained within Appendix B.
Example 1: Using only the RS485 / Modbus communications interface
SF82 Transmitter User Manual
Power
+24 V
Supply +ve
Moisture
Power Supply
Transmitter
4...20 mA
Signal Return Input
Example 2: Using both the 4...20 mA & RS485 / Modbus communication interfaces
simultaneously
+24 V
Power Supply
4...20 mA
Signal Return
To RS485 Modbus Network/Device
Power
Supply +ve
Modbus A+B
Moisture
Transmitter
0 V
4...20 mA
Signal Return
Modbus A+B
+ve−ve
Current Measurement Device
Monitor/PLC/DCS etc.
8 97576 Issue 1.2, March 2022
To RS485 Modbus Network/Device
Page 17
SF82 Transmitter User Manual
2.2.5 Cable Selection for Self-Assembled Cables
It is recommended to use 3-core screened cable. For short runs, a cable with individual
conductor sizes of 24 AWG / 0.21mm2 would be a typical choice. For longer runs, a
cable with larger conductors may be required to keep loop resistance within allowable
limits. A chart of maximum loop resistance vs supply voltage is provided in the following
section to aid in cable selection.
2.2.6 Maximum Loop Resistance vs Supply Voltage
INSTALLATION
Figure 7
NOTE: Cable resistance of the entire loop must be considered when calculating loop
resistance.
Maximum Load of SF82 – Including Cable Resistance
Michell Instruments 9
Page 18
INSTALLATION
2.3 Transmitter Mounting
2.3.1 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)
SF82 Transmitter User Manual
2.3.2 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).
2.3.3 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)
10 97576 Issue 1.2, March 2022
Page 19
SF82 Transmitter User Manual
2.3.4 Transmitter Mounting – Sample Block (Optional)
These procedures must be carried out by a qualied
installation engineer.
2.3.4.1 Sample Block Gas Connections
Sample gas connections are made to the Gas In and Gas Out ports on the sample block
see
Figure 8.
for connection purposes the ports are interchangeable).
Normally, connections are made via stainless steel pipework, in which case the sensor
block/transmitter assembly will be self supporting. If PTFE tubing is used it may be
necessary to support the assembly with a body clip.
Either port on the sample block may be used as the Gas Input port (i.e.
1
INSTALLATION
2
3
4
5
Figure 8
2345
1
Sample Block Gas Connections
6
5
4
3
2
1
Both the Input and Output gas connections are ⅛” NPT. It is recommended that both
the Gas Input and Output connections are made via ⅛” NPT to 6mm or ⅛” NPT to
¼” stainless steel tube adaptors (2 to 5 –
Figure 8)
. The method of connection to the
sensor block (6) is as follows:
NOTE: The following description relates to 6mm tube fixings. The sample
block ports are both ⅛” NPT female process connections. Tube adaptors are
not supplied with the equipment but can be obtained by contacting your local
distributor or Michell Instruments (see www.michell.com for details).
1. Cut a suitable length of 6mm (¼” U.S.) stainless steel tubing (1) and,
if necessary, bend to shape to suit the location of the sensor block
assembly. NOTE: To facilitate ease of connection to the port, at
least 75mm (3”) of the tubing coming out of the Gas In port
should be straight.
2. Clean and deburr the inside and outside rim of the tubing at the connection
point.
3. Using gas-fitters PTFE tape, wrap the NPT thread 2–3 times. The wrapping
should leave the first thread clear and follow the direction of the thread.
4. Screw the ⅛” NPT Swagelok adaptor (5) into the ⅛” NPT inlet port in
the sensor block (6) and tighten to a torque setting of 35 Nm (25 lbf-ft).
Michell Instruments 11
Page 20
INSTALLATION
5. Pass the stainless steel tubing (1) through the locking nut (2). NOTE:
Threads towards the gas port.
6. Fit the back ferrule (3) over the stainless steel tubing (1) with the bevelled
end facing the back of the front ferrule (4).
7. Place the front ferrule (4) over the stainless steel tubing (1), bevelled end
towards the adaptor (5).
8. Push the stainless steel tubing (1) as far as it will go into the adaptor (5)
and tighten up the locking nut (2) finger tight.
9. Hold the adaptor (5) flats with a spanner and tighten up the locking
nut (2) to a torque setting of 35 Nm (25 lbf-ft) (1¼ turns). This action
compresses the front ferrule (4) and back ferrule (3) onto the tubing to
form a gas tight seal.
10. Connect up the other gas port as described in steps 1 to 9 above.
2.3.4.2 Sensor Installation
SF82 Transmitter User Manual
To mount the transmitter into the sensor block (preferred method), proceed as follows,
refer to
1. Ensure that the protective cover (2), and its desiccant capsule (2a), have
2. Fit the bonded seal (4) over the threaded part of the transmitter body.
3. Screw the transmitter (1) into the sample block (3) and tighten to the
4. Fit the transmitter cable/connector assembly to the plug located on the
Figure 9.
been removed from the tip of the transmitter.
recommended torque setting. NOTE: Use the flats of the hexagonal
nut and not the sensor body.
base of the transmitter and tighten the fixing screw (see Section 2.3.4.1).
WARNING: Under no circumstances should the sensor
guard be handled with the ngers.
2
2a
1
3
4
Figure 9
Transmitter Mounting – Sensor Block
12 97576 Issue 1.2, March 2022
Page 21
SF82 Transmitter User Manual
2.3.5 Transmitter Mounting – Direct Pipeline Connection
INSTALLATION
The transmitter may be directly mounted into a pipe or duct, as shown in
Figure 10.
CAUTION: Do not mount the transmitter too close to the
bottom of a bend where any condensate in the pipeline
might collect and saturate the probe.
The pipe or duct will require a thread to match the transmitter body thread. Fixing
dimensions are shown in
Figure 10
. 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.
The following procedure must be carried out by
competent personnel.
1. Ensure that the blue protective cover (and its desiccant capsule) has been
removed from the tip of the transmitter.
WARNING: Under no circumstances should the
sensor guard be handled with the fingers.
2. Fit a bonded seal (2) over the threaded part of the transmitter body.
3. Screw the transmitter (3) into the pipe (1). Tighten enough to obtain a
gas tight seal. (Torque will depend upon the pipeline material.) NOTE: Do
not overtighten or the thread on the pipework may be stripped.
1
2
3
1
2
3
Figure 10
48mm
Transmitter Mounting – Pipe or Duct
Michell Instruments 13
Page 22
INSTALLATION
2.3.6 Transmitter Mounting – With Additional Process Connection Adapter
SF82 Transmitter User Manual
!
To mount the adapter into the transmitter, proceed as follows (see
1. Ensure that the protective cover (2), and its desiccant capsule (2a), have
been removed from the tip of the transmitter.
2. Fit the bonded seal (3) over the threaded part of the transmitter body.
3. Screw the adapter (4) onto the threaded part of the transmitter and tighten
to torque settings recommended in Section 4. NOTE: Use the flats of the
hexagonal nut and not the sensor body.
!
4. Screw the transmitter (1) with its seal (3) and adapter (4) into the sample
block (see Section 2.3.4) or pipeline (see Section 2.3.5) and fully tighten
using a wrench until the seal is fully compressed and to the following torque
settings:
The following procedure must be carried out by a qualied
installation engineer.
Figure 11)
WARNING: Under no circumstances should the sensor guard be
handled with the ngers.
:
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
NOTE: Use the ats of the hexagonal nut and not the sensor body.
2
2a
4
1
3
Figure 11
Transmitter Mounting with Adapter
14 97576 Issue 1.2, March 2022
Page 23
SF82 Transmitter User Manual
r
3 MAINTENANCE
3.1 Maintenance and Calibration
Routine maintenance of the SF82 Transmitter is confined to regular re-calibration. For
most applications, annual re-calibration ensures that the stated accuracy of the SF82
Transmitter is maintained.
Specialist calibration instrumentation is required to calibrate the transmitter and a true
calibration can only be performed by exposure of the dew-point sensor to a reference
gas of known dew point.
Calibration services are offered by Michell Instruments at their accredited calibration
laboratories. All calibrations are traceable to national standards either via the National
Physical Laboratory (UK) or the National Institute of Standards and Technology (USA).
The SF82 transmitter can be returned to Michell Instruments either directly or via the
authorized distributor, for calibration.
MAINTENANCE
Alternatively, Michell Instruments can provide an exchange transmitter. Prior to recalibration, an exchange transmitter can be ordered from Michell Instruments or an
authorized distributor.
Once the replacement transmitter and calibration certificate have been received, the
original transmitter can be disconnected and the replacement transmitter fitted in its
place. The original transmitter should be packed in its original packing, if possible, and
returned to Michell Instruments, either directly or via an authorized agent.
Sensor Guard Replacement
The sensor is supplied with a white HMWPE 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
discoloration. When replacing a guard, make sure to wear clean disposable gloves, and
handle by the threaded base section only.
Replacement HMWPE or stainless steel guards can be ordered from your Michell
Instruments representative.
HANDLE,
USING
GLOVES, BY
BLACK PART
ON LY
E
n
e
H
m
C
u
I
r
6
t
s
0
M
n
9
I
0
Figure 12
Replacement of HMWPE Guard
Michell Instruments 15
Page 24
MAINTENANCE
Bonded Seal
If the supplied bonded seal is damaged or lost, a pack of 5 replacement bonded seals
can be obtained by your Michell Instruments representative.
O-ring Seal
If the supplied O-ring seal is damaged or lost a pack of 5 replacement O-ring seals
can be obtained by contacting your Michell Instruments representative.
SF82 Transmitter User Manual
16 97576 Issue 1.2, March 2022
Page 25
SF82 Transmitter User Manual
4 MEASUREMENT GUIDE
4.1.1 Sampling Considerations
There are two basic methods of measuring a sample with the SF82 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.
Examples of such conditional limitations are:
• Excessive flow rate
MEASUREMENT GUIDE
• Presence of particulates matter
• Presence of entrained liquids
• Excessive sample temperature
The basic considerations for each measurement type are as follows:
Michell Instruments 17
Page 26
MEASUREMENT GUIDE
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.
SF82 Transmitter User Manual
A
1 2
B
C
1. Purge Inlet
2. Gas Outlet
Figure 13
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.
Installation Location
Figure 14
18 97576 Issue 1.2, March 2022
Installation Location
Page 27
SF82 Transmitter User Manual
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 HMWPE (10μm pore size) or Stainless Steel (80μm 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 ltration.
MEASUREMENT GUIDE
4. Sample Temperature – Although the SF82 can be operated at sample
temperatures up to 60°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 4.1.2, 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.
Michell Instruments 19
Page 28
MEASUREMENT GUIDE
4.1.2 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.
SF82 Transmitter User Manual
Figure 15
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
porous medium causing water to migrate into the pressurized 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.
Material Permeability Comparison
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.
20 97576 Issue 1.2, March 2022
Page 29
SF82 Transmitter User Manual
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.
MEASUREMENT GUIDE
Figure 16
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.
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.
Dead volume
Michell Instruments 21
Page 30
MEASUREMENT GUIDE
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.
SF82 Transmitter User Manual
• 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.
22 97576 Issue 1.2, March 2022
Page 31
SF82 Transmitter User Manual
APPENDIX A
Appendix A
Technical Specications
Michell Instruments 23
Page 32
APPENDIX A
SF82 Transmitter User Manual
Appendix A Technical Specications
Performance Specications SF82 MiniDIN 43650 SF82 M12
Measurement Range (Dew Point) -60°C to +60°C (-76°F to +140°F) dew point
Accuracy (Dew Point) ±2°C dew point*
Response Time
Repeatability 0.5°C (0.9°F) dew point
Calibration 9-point calibration certicate traceable to national standards
Electrical Specications
Output Signal
Moisture Output Dew point or moisture content
Temperature Output Not available Data via Modbus RTU
Analog Output Scaled Range
4...20 mA (Dew point)
Analog Output Scaled Range
4...20 mA (Moisture Content in Gas)
Supply Voltage 6.5 to 28 V DC 5 to 28 V DC
Load Resistance Max 250 Ω @ 12 V (500 Ω @ 24 V)
Current Consumption 23 mA max Analog only 23 mA max, digital only 6 mA max
Electrical Safety IEC61010-1, UL61010-1 & CAN/CSA C22.2 No. 61010
User congurable over range; 4...20 mA (2-wire
connection, current source)
Operating Specications
Operating Temperature -20°C to +60°C (-4°F to +140°F)
Compensated Temperature Range -20 to +50°C (-4°F to +122°F)
Storage Temperature
Maximum Operating Pressure
Pressure Safety Rating
Flow Rate 1 to 5 Nl/min mounted in standard sampling block; 0 to 10 m/sec direct insertion
Mechanical Specications
Ingress Protection
Housing Material 316 stainless steel
Dimensions L = 133 mm x ø45 mm (with connector cable) L = 156 mm x ø45 mm (with connector cable)
Filter (Sensor Protection)
Process Connection
Weight 150 g (excluding connector cable)
Electrical Connections MiniDIN 43650 form C M12 5 pin (A coded)
Mating Electrical Connectors
Diagnostic Conditions
(Factory Programmed)
* Over Compensated Temperature Range
IP66 in accordance with BS EN 60529 (current version):
NEMA 4 ingress protection in accordance with NEMA 250
Optional 0.8, 2, 5, 10 metre (2.62, 6.5, 16.4, 32.81 foot)
Sensor fault
Under-range dew point
Over-range dew point
(current version)
Mating connector supplied as standard
MiniDIN connector/cable available
63% at room temperature at 1 bara
-60°C to -20°C (-76°F to -4°F dew point: 6 s
-20°C to -60°C (-4°F to -76°F dew point: 40 s
User congurable over range; 4...20 mA (2-wire connection,
current source) Modbus RTU over RS485 digital communications
-60 °C to +60°C (-7 6°F to +140°F ) dew point
-50 °C to +50°C (-5 8°F to +122°F ) dew point
-50 °C to +30°C (-5 8°F to +86°F) dew point
-80 °C to +20°C (-1 12°F to +68°F )dew point
-20 °C to +50°C (-4 °F to +122°F) dew point
(Non standard ranges available on request)
(Non standard ranges available on request)
10 MPag (100 barg/1450 psig) maximum
45 MPag (450 barg/ 6526.7 psig) maximum
Optional: 316 stainless steel sintered guard <80 µm
0 to 24000 ppm
-40°C to +60°C (-40°F to +140°F)
Standard: HMWPE <10µm)
5/8” - 18 UNF
3/4” - 16 UNF
G1/2” - BSP
V
IEC61010-1, UL61010-1 & CAN/CSA C22.2 No. 61010
Optional 0.8 , 2, 5, 10 meter (2.62, 6.5, 16.4, 32.81 foot) M12 A
23 mA
4 mA
20 mA
EN61373 Rail Rolling Stock
EN50121-3-2 Rail EMC/RFI
coded connector/cable available
IP65
24 97576 Issue 1.2, March 2022
Page 33
SF82 Transmitter User Manual
A.1 Dimensions
M12, 5/8” UNF
APPENDIX A
M12, G1/2
M12, 3/4” UNF
Michell Instruments 25
Page 34
APPENDIX A
MiniDIN, 5/8” UNF
SF82 Transmitter User Manual
MiniDIN, G1/2
MiniDIN, 3/4” UNF
26 97576 Issue 1.2, March 2022
Page 35
SF82 Transmitter User Manual
G1/2
APPENDIX A
5/8” UNF
3/4” UNF
Quick Connect
Michell Instruments 27
Page 36
APPENDIX B
SF82 Transmitter User Manual
Appendix B
Modbus Register Map
28 97576 Issue 1.2, March 2022
Page 37
SF82 Transmitter User Manual
Appendix B Modbus Register Map
All the data values relating to the SF82 are stored in 16-bit wide holding registers.
Registers can contain either measured or calculated values (dew-point, temperature,
etc.), or configuration data (output settings).
Modbus RTU Implementation
This is a partial implementation of the Modbus RTU Standard with the following codes
implemented:
Function Code Description
3 Read Holding Register
6 Write Holding Register
16 Write Multiple Holding Registers
Register Types
Data Types Description
uint16 16-bit insigned integer, can contain options
list e.g. 0 = Dew Point, 1 = Temperature
int16 16-bit signed integer
int32 32-bit signed integer, stored
across 2 16-bit registers
oat IEEE754 single precision floating pint,
stored across 2 16-bit registers
APPENDIX B
Serial Port Settings (RS485)
9600 Baud Rate, 8 Data Bits, No Parity, 1 Stop Bit, No Flow Control
http://www.simplymodbus.ca/FAQ.htm is an excellent resource
covering the basics of the Modbus protocol. Full descriptions
of the function codes (FC03/FC06/FC16) can be found in the
sidebar.
https://www.scadacore.com/tools/programming-calculators/
online-hex-converter/ is an excellent resource for determining
register types/byte order issues in raw received Modbus data.
Michell Instruments 29
Page 38
APPENDIX B
SF82 Transmitter User Manual
Register Address
Dec Hex Access Data Type Description Comments
0 00 R uint16 Instrument Modbus Address
1 01 R uint16 Instrument ID
Batch 0xA123
2 02 R uint16 Sensor Batch Number
3 03 R uint16 Sensor Serial Number
4 04 R uint16 Firmware Version Divide by 1000, i.e. 12003 = V12.003
5 05 R uint16 Register Map Version Divide by 1000, i.e. 12003 = V12.003
6 06 R uint16 Year of Calibration
7 07 R uint16 Month of Calibration
8 08 R uint16 Day of Calibration
14 0E R special Status
Serial 0x0001
Complete sensor serial would be A123-001
bit0 = Dew-point Sensor Short
bit1 = Dew-point Sensor Open
bit2 = Temperature Sensor Short
bit3 = Temperature Sensor Open
bit4 = Analog Output Under-Range
bit5 = Analog Output Over-Range
bit6 = Analog Output Out-Of-Range
...
bit14 = Memory Fault
bit15 = Hardware Fault
17 11 R oat Dew Point (High Word)
18 12 Dew Point (Low Word)
19 13 R oat Temperature (High Word)
20 14 Temperature (Low Word)
21 15 R oat ppmV Ideal Gas (High Word)
22 16 ppmV Ideal Gas (Low Word)
101 65 R/W oat Pressure Value (High Word) Used for ppmV Ideal Gas calculation
102 66 Pressure Value (Low Word)
0 = O
110 6E R/W uint16 Analog Output Parameter
111 6F R/W oat
112 70
113 71 R/W oat
114 72
Analog Output Range Low
(High Word)
Analog Output Range Low
(Low Word)
Analog Output Range High
(High Word)
Analog Output Range High
(Low Word)
1 = Dew Point
2 = Temperature
3 = ppmV Ideal Gas
This value is clipped when parameter is
changed. See parameter ranges below
This value is clipped when parameter is
changed. See parameter ranges below
30 97576 Issue 1.2, March 2022
Page 39
SF82 Transmitter User Manual
Dec Hex Access Data Type Description Comments
120 78 R/W uint16
121 79 R/W uint16
122 7A R/W uint16
123 7B R/W uint16
Analog Output, Under-Range
Output
Analog Output, Over-Range
Output
Analog Output, Dew-Point
Sensor Fault
Analog Output, Temperature
Sensor Fault
Parameter Ranges Min Max
Dew Point -150 250
Temperature -150 250
ppm
V
0 30000
0 = None
1 = Low Alarm (3.5ma)
2 = High Alarm (23ma)
3 = Minimum Scale (4ma)
4 = Maximum Scale (20ma)
5 = Namur Low Alarm (3.7ma)
6 = Namur High Alarm (20.5ma)
APPENDIX B
Michell Instruments 31
Page 40
APPENDIX C
SF82 Transmitter User Manual
Appendix C
Quality, Recycling
& Warranty
Information
32 97576 Issue 1.2, March 2022
Page 41
SF82 Transmitter User Manual
Appendix C Quality, Recycling & Warranty Information
Michell Instruments is dedicated to complying to all relevant legislation and directives.
Full information can be found on our website at:
www.michell.com/compliance
This page contains information on the following directives:
• Anti-Facilitation of Tax Evasion Policy
• ATEX Directive
• Calibration Facilities
• Conflict Minerals
• FCC Statement
• Manufacturing Quality
APPENDIX C
• Modern Slavery Statement
• Pressure Equipment Directive
• REACH
• RoHS3
• WEEE2
• Recycling Policy
• Warranty and Returns
This information is also available in PDF format.
Michell Instruments 33
Page 42
APPENDIX D
SF82 Transmitter User Manual
Appendix D
Return Document &
Decontamination Declaration
34 97576 Issue 1.2, March 2022
Page 43
SF82 Transmitter User Manual
Appendix D Return Document & Decontamination Declaration
Decontamination Certicate
IMPORTANT NOTE: Please complete this form prior to this instrument, or any components, leaving your
site and being returned to us, or, where applicable, prior to any work being carried out by a Michell
engineer at your site.
Instrument Serial Number
Warranty Repair? YES NO Original PO #
Company Name Contact Name
Address
Telephone # E-mail address
Reason for Return /Description of Fault:
APPENDIX D
Has this equipment been exposed (internally or externally) to any of the following?
Please circle (YES/NO) as applicable and provide details below
Biohazards YES NO
Biological agents YES NO
Hazardous chemicals YES NO
Radioactive substances YES NO
Other hazards YES NO
Please provide details of any hazardous materials used with this equipment as indicated above (use continuation sheet
if necessary)
Your method of cleaning/decontamination
Has the equipment been cleaned and decontaminated? YES NOT NECESSARY
Michell Instruments will not accept instruments that have been exposed to toxins, radio-activity or bio-hazardous
materials. For most applications involving solvents, acidic, basic, ammable or toxic gases a simple purge with dry
gas (dew point <-30°C) over 24 hours should be sufcient to decontaminate the unit prior to return.
Work will not be carried out on any unit that does not have a completed decontamination declaration.
Decontamination Declaration
I declare that the information above is true and complete to the best of my knowledge, and it is safe for Michell
personnel to service or repair the returned instrument.
Name (Print) Position
Signature Date
F0121, Issue 2, December 2011
Michell Instruments 35
Page 44
www.ProcessSensing.com
http://www.michell.com
Loading...