FT Technologies FT742-D-SM User manual

1 FT742-SM (RS422 & RS485) Sensors –User Manual
FT TECHNOLOGIES LTD.
SUNBURY HOUSE
BROOKLANDS CLOSE
SUNBURY-ON-THAMES
MIDDLESEX TW16 7DX
TEL: [phone]
FAX: [phone]
WEB: www.fttechnologies.com
E-MAIL: [e-mail]
A4281-4-EN
October 2021The FT and Acu-Res logos are registered trademarks of FT Technologies Ltd.
Copyright © 2021 FT Technologies Ltd. All rights reserved.
FT742-D-SM –Digital Wind Sensor User Manual
Surface-Mounted - Digital RS422 & RS485 options

2 FT742-SM (RS422 & RS485) Sensors –User Manual
Contents
Product Symbols......................................................................................................4
Safety Instructions...................................................................................................5
Consignes de sécurité.............................................................................................6
1INTRODUCTION................................................................................................. 7
1.1 Product Overview ................................................................................................................7
1.2 Build Versions and Labelling .............................................................................................7
1.3 Scope of Use........................................................................................................................7
1.4 Disclaimer.............................................................................................................................8
2FUNCTIONAL DESCRIPTION ...........................................................................9
2.1 Technical Performance .......................................................................................................9
2.2 Wind Speed Calibration ....................................................................................................10
2.3 Wind Speed and Direction Filtering.................................................................................10
2.4 Electronically Offsetting the Wind Direction Datum......................................................11
2.5 Compass & Declination Angle Operation .......................................................................11
2.5.1 Compass Calibration.......................................................................................................11
2.6 Selective Filter Scheme.....................................................................................................11
2.7 Error Detection...................................................................................................................11
2.8 Overspeed Warning Scheme............................................................................................12
2.9 Heater Setup.......................................................................................................................12
2.10 Low Power Operation........................................................................................................12
2.11 Acoustic Temperature.......................................................................................................13
3MECHANICAL & ELECTRICAL INSTALLATION............................................14
3.1 FT742-SM Sensors.............................................................................................................14
3.1.1 Mechanical & Electrical Integration .................................................................................14
3.1.2 Connector Details............................................................................................................17
3.1.3 Lightning, Surge & EMI Protection..................................................................................17
4SERVICE, CONFIGURATION & TESTING...................................................... 19
4.1 Inspection...........................................................................................................................19
4.2 Fault Finding & Troubleshooting.....................................................................................20
4.3 Returns ...............................................................................................................................20
5ACU-TEST EVALUATION KIT......................................................................... 21
5.1 Evaluation Pack .................................................................................................................21
5.2 Software Installation..........................................................................................................22
5.3 Acu-Vis 2.0 Software Operation .......................................................................................23
5.4 Command Line Terminal Programs (Including TeraTerm)............................................28

3 FT742-SM (RS422 & RS485) Sensors –User Manual
6SENSOR COMMUNICATION...........................................................................30
6.1 Introduction........................................................................................................................30
6.2 RS422 & RS485 Protocol...................................................................................................30
6.3 Configuring the Sensor.....................................................................................................33
6.4 Communication..................................................................................................................33
6.4.1 Conventions used in this manual ....................................................................................33
6.4.2 Data Transmission ..........................................................................................................34
6.4.3 Message Format..............................................................................................................34
6.4.4 Listener and Talker Identifiers.........................................................................................35
6.4.5 Calculating the Message Checksum...............................................................................35
6.4.6 Disabling the Checksum..................................................................................................35
7PARAMETER SETTINGS ................................................................................37
7.1 Command Types................................................................................................................37
7.1.1 Set Commands................................................................................................................37
7.1.2 Query Commands ...........................................................................................................38
7.2 User Calibration Table.......................................................................................................39
7.3 Timing Constraints............................................................................................................40
7.4 Command Parameters.......................................................................................................41
7.4.1 AM: Set or Query Anemometer Mount Orientation .........................................................41
7.4.2 AT.1: Query the Acoustic Temperature...........................................................................42
7.4.3 AT.2: Set or Query the Acoustic Temperature Units.......................................................43
7.4.4 AT.3 Set or Query the Acoustic Temperature Filter Length............................................44
7.4.5 BR: Set or Query the Serial Interface Baud Rate............................................................45
7.4.6 CF: Set or Query the Wind Compass Settings................................................................46
7.4.7 CU: Set or Query the Continuous Update Setting...........................................................48
7.4.8 DF: Set or Query the Wind Velocity Data Format...........................................................50
7.4.9 DG: Query the Run-time Counter....................................................................................52
7.4.10 DL: Set or Query the Command Delay Interval ..........................................................53
7.4.11 ER: Query or Reset the Error Report..........................................................................54
7.4.12 FL.1: Set or Query General Filter Settings .................................................................55
7.4.13 FL.2: Set or Query Filter Lengths................................................................................56
7.4.14 FL.3: Set or Query the Selective Filter........................................................................57
7.4.15 HT.1: Set or Query General Heater Settings..............................................................58
7.4.16 HT.2: Set or Query Delay Heater Settings..................................................................59
7.4.17 ID: Set or Query the Listener & Talker Identifiers.......................................................60
7.4.18 MM: Reset or Query the Min/Max Recorded Wind Speed..........................................61
7.4.19 OS: Set or Query Overspeed Warning Scheme........................................................62
7.4.20 RS: Reset the Sensor .................................................................................................63
7.4.21 SN: Query the Serial Number and Platform Version ..................................................64
7.4.22 SV: Query the Software Version.................................................................................65
7.4.23 UC.1: General User Calibration Settings....................................................................66
7.4.24 UC.2: Clear User Calibration Table Record................................................................67
7.4.25 UC.3: Set User Calibration Table Record...................................................................68
7.4.26 UC.4: Save and Read User Calibration Table............................................................69
7.4.27 UC.5: Set & Query User Calibration Table Label .......................................................70
7.4.28 US: Set or Query Saved Parameters..........................................................................71
7.4.29 WV Polar: Query the Wind Velocity Reading..............................................................73
7.4.30 WV NMEA: Query the Wind Velocity Reading............................................................75

4 FT742-SM (RS422 & RS485) Sensors –User Manual
Product Symbols
The following symbols may be used upon the product and within the manual.
Meaning / Description
Symbol
Signification / Description
Warning/ Caution
An appropriate safety instruction should be
followed or caution to a potential hazard
exists
Avertissement / Attention
Une instruction de sécurité doit être
suivie ou attention portée à un
danger potentiel qui existe.
DC Current only
Equipment operates under Direct Current
(DC) supply only.
Courant continu uniquement
L'équipement fonctionne sous une
alimentation en courant continu (CC)
uniquement.
Recognized Component
Sensors marked with the ETL label indicate
that the product conforms to UL Standard
61010-1 and is certified to CSA Standard
C22.2 No. 61010-1.
4000105
Composant Reconnu
Les capteurs marqués avec
l’étiquette ETL indiquent que le
produit est conforme à la norme UL
61010-01 et est certifié à la norme
CSA22.2 61010-01.
Product Disposal
In accordance with European directive
2012/19/EU on Waste Electrical and
Electronic Equipment (WEEE), these
product components must be recycled. This
should be done by returning the product to
FT Technologies or by using an appropriate
waste disposal company. This product
should not be disposed of in general waste
of landfill. This product complies with the
RoHS2 (2011/65/EU) directive.
Élimination du produit
Conformément à la directive
européenne 2012/19/EU relative aux
déchets d'équipements électriques et
électroniques (DEEE), ces
composants du produit doivent être
recyclés. Cela doit être fait par le
retour du produit à FT Technologies
ou en utilisant une entreprise
d'élimination de déchets. Ce produit
ne doit pas être éliminé avec les
ordures ménagères ou en décharge.
Ce produit est conforme à la
directive RoHS2 (2011/65/EU).
CE Mark
The EU Declaration of Conformity
complies with the essential requirements
of the following applicable EMC Directive
2014/30/EU, and carries the CE Marking
accordingly.
Marquage CE
Déclaration de conformité CE de la
compatibilité électromagnétique
(EMC) et marquage CE
conformément à la directive CE
2014/30/EU.

5 FT742-SM (RS422 & RS485) Sensors –User Manual
Safety Instructions
English
•To ensure the safe installation and operation of this product the equipment must be installed and
integrated:
oUsing suitably qualified and trained personnel
oIn accordance with any regional electrical codes
oIn accordance with the instructions set out in this manual, observing all information, warnings
and instructions
oIn accordance with any other instructions or guidance FT Technologies provide
•To ensure that the product remains compliant with the electrical safety requirements of the UL / CSA
61010-1 Standards it must be;
oConnected to a regionally approved limited PSU rated 6-30VDC (current limited 2.5A
maximum)
oProtected by UL 1449 listed surge protection devices
oConnected with an approved interface cable (for example UL/ CSA recognised AWM style
21198, rated 300V, 80°C)
•The equipment must only be operated within the range of the specified technical data and used for the
purposes for which it was designed.
•The equipment should always be transported in packaging which is appropriate, that will prevent any
accidental damage from occurring.
•Always ensure that any failures or errors from the product cannot cause any damage to any other
equipment or property or cause any other consequential effects.

6 FT742-SM (RS422 & RS485) Sensors –User Manual
Consignes de sécurité
Français
•Pour assurer la sécurité de l'installation et le fonctionnement de ce produit, l'équipement doit être
installé et intégré :
oÀ l'aide de personnel qualifié et formé
oConformément à tous les codes électriques régionaux
oConformément aux instructions figurant dans ce manuel et en observant toutes les
informations, avertissements et instructions
oConformément à d'autres instructions ou directives que FT Technologies fournit
•Pour garantir que le produit reste compatible avec les exigences de sécurité électrique de l'UL/CSA
61010-1 normes, l'équipement doit être :
oConnecté à une alimentation agréée régionalement convenablement isolée de tension
nominale 6-30 VCC et avec courant limité (2.5 A maximum)
oProtégé par des dispositifs de protection UL 1449 contre les surtensions
oConnecté avec un câble d'interface (par exemple UL/CSA reconnu AWM style 21198, de
valeur nominale 300 V, 80°C)
•L'équipement doit être utilisé uniquement dans la plage des données techniques spécifiées et utilisé
aux fins pour lesquelles il a été conçu.
•L'équipement doit toujours être transporté dans un emballage qui est approprié, qui permettra d'éviter
qu'un quelconque dommage accidentel ne survienne.
•En toutes circonstances, garantir que les défaillances ou les erreurs du produit ne puissent pas causer
des dommages à d'autres équipements ou autres biens ou provoquer d'autres effets indirects.

Section 1 Introduction
7 FT742-SM (RS422 & RS485) Sensors –User Manual
1 INTRODUCTION
1.1 Product Overview
The FT742-SM is a solid-state ultrasonic wind sensor, using a patented Acoustic Resonance airflow
sensing technique to measure accurately both wind speed and direction. The sensors have been
specifically designed to operate in harsh environments including offshore and ice-prone areas. The
wind sensor has no moving parts to degrade or wear and is designed for applications requiring high
reliability. This helps reduce costly down-time and unscheduled maintenance visits.
Mounting and aligning the sensor is very simple. A wind datum feature mark can be used to align the
sensor to a reference point, while the integrated compass allows reference to magnetic North. For
operation in ice-prone areas, the FT742 is fitted with a thermostatically controlled all-body heating
system. A two-element heater is used to ensure heat is evenly distributed over the entire surface area.
The FT742-SM allows either RS422 (full-duplex) or RS485 (half-duplex) communication outputs, this
communication setting is programmed at the factory and cannot be modified by the user.
1.2 Build Versions and Labelling
Figure 1 shows how to identify the sensor platform version and individual serial number, depending on
the attached main labels:
Additional labels may be attached.
Figure 1: Main Sensor Labels
1.3 Scope of Use
The sensor is designed, manufactured and optimised for high availability.
No promise in part or full can be given to guarantee a sensor’s continuous operation, as exceptional
circumstances can occur that may result in the failure of the output from a sensor. Exceptional
circumstances can include:
•Poor installation
•Inadequate inspection
•Power supply failures
•Poor quality electrical connections
•Lightning exposure
•Problematic environmental conditions or combination of conditions
•Physical Damage

Section 1 Introduction
8 FT742-SM (RS422 & RS485) Sensors –User Manual
Typically higher levels of wind speed and wind direction data availability are achieved through the use
of an additional FT sensor or alternative sensor. Control strategies or algorithms, which compensate in
whole or in part, for any temporary interruption of data from individual sensors should also be applied.
The choice and implementation of such methods is entirely the Purchaser’s responsibility.
1.4 Disclaimer
There are no warranties, representations or conditions, expressed or implied of any kind given in this
manual for any particular design application. The Purchaser should independently undertake sufficient
testing to confirm validity and suitability of any design. The Purchaser assumes all risks and liability in
conjunction with the use of the information given.
Any warranty given by FT Technologies in respect of the Equipment is conditional upon the sensor
being handled, installed, integrated and operated in accordance within the guidelines given in this
manual.
FT Technologies can take no responsibility for the effectiveness of any sensor lightning protection
scheme implemented. The wind sensor has passed a wide range of EMC tests but FT Technologies
does not warrant the sensor to survive lightning strikes.
Information supplied by FT Technologies Ltd. shall not be construed as permission to license to operate
under, or recommendation to infringe any existing or pending patent, patent applications or trademarks.

Section 2 Functional Description
9 FT742-SM (RS422 & RS485) Sensors –User Manual
2 FUNCTIONAL DESCRIPTION
2.1 Technical Performance
Sensor Performance1 & 2
Measurement Principle Acoustic Resonance (compensated against variations in temperature,
pressure and humidity)
Wind Speed Measurement
Range 0-75m/s
Resolution 0.1m/s
Accuracy ±0.3m/s (0-16m/s)
±2% (16m/s-40m/s)
±4% (40m/s-75m/s)
Wind Direction Measurement
Range 0 to 360°
Sensor Accuracy 4RMS
Compass Accuracy 5RMS
Resolution 1
Acoustic Temperature Measurement
Units Celsius, Fahrenheit or Kelvin
Resolution 0.1°
Accuracy ±2°C under the following conditions:
Wind speed between 5m/s and 60m/s
Temperature Difference < 10°C (Sensor Temp. vs Air Temp.)
Operating (air) temperature between -20°C and +60°C
Environment
Temperature Range -40 to +85C (operating and storage)
Humidity 0-100%
Altitude 0-4000m
Data I/O
Interface RS422 (full-duplex) or RS485 (half-duplex). The communications
interface option is programmed at the factory.
Format ASCII, polled or Continuous Update modes
(CU mode using RS485HD requires software V7.4+)
Data Update Rate Up to 10 measurements per second (10Hz)
Power Requirements3, 4 & 5
Supply Voltage 24VDC nominal (6-30VDC range). A minimum of 9VDC is required
for heater operation
Sensor Current (Heater off) 25mA nominal (29mA with compass enabled)
Heater Current (Heater on)6 Up to 2A + nominal
Physical
Weight 252g
Material Aluminium alloy (external body hard anodised)
I/O Connector 8-way M12 connector
Mounting Method Surface-Mount with compressed O-ring/screw fit
Notes:
1.All specifications subject to change without notice.
2.Specifications calculated with the default settings and filters enabled.
3.See safety instruction requirements (page 5 and 6).
4.The heater set-point temperature can be configured by the user. Modifications to the heater current
limit and under-voltage limit are not permitted on the FT742-SM range, for further details contact FT
Technologies.

Section 2 Functional Description
10 FT742-SM (RS422 & RS485) Sensors –User Manual
5.The current draw from the heater will depend on the environmental cooling and the temperature
setpoint. The sensor is limited to 2A4 nominal by default. The maximum power is 60W (30V & 2A).
6.A suitable PSU capable of providing up to 2.5A maximum is recommended.
2.2 Wind Speed Calibration
The wind sensor is calibrated in our wind tunnels before dispatch. As the sensor has no moving parts, there is
no need to recalibrate a sensor over its lifetime as no measurement degradation will occur. The sensor’s compact
strong monolithic shape is designed to prevent accidental transducer movement or damage. FT Technologies’
calibration procedure and wind tunnels are designed to give a calibration profile that is within the accuracy limits
set in the product technical specification (see Section 2.1). Periodically the accuracy of FT’s wind tunnels are
compared with the accuracy of an independent wind tunnel to ensure that no drift has occurred.
In exceptional circumstances users may wish to apply additional calibration factors. The sensors have an option
to set a User Calibration Table, which can modify the wind sensor’s wind speed output (see Section 7.4.23).
The User Calibration Table can be programmed with up to 64 correction factors which are maintained in non-
volatile memory. When enabled, the uncorrected wind speed output is adjusted according to the stored User
Calibration Table records using linear interpolation. The adjustments are applied to wind speed readings
regardless of wind direction.
2.3 Wind Speed and Direction Filtering
It is important that the system does not rely exclusively on a single wind reading for any control decision. A single
reading may be inaccurate due to measurement error, turbulence, corruption or interference. It is recommended
that an average of wind readings is used. In addition if 100% data availability is required then a second FT sensor
or alternative wind sensors should be fitted in addition.
The sensor has optional internal filtering available. This is a digital finite impulse response (FIR) filter, which works
by calculating the moving average of a fixed number of previous readings. If filtering is being applied externally,
the sensor’s output filters can be disabled. If filtering inside the sensor is preferred, the length of the averaging for
both wind speed and direction can be independently set (See Sections 7.4.12 and 7.4.13).
Figure 2: Examples of FIR Filtering
It is recommended to use average readings to reduce the effects of air turbulence.

Section 2 Functional Description
11 FT742-SM (RS422 & RS485) Sensors –User Manual
2.4 Electronically Offsetting the Wind Direction Datum
For applications where the compass is not being used, the wind direction datum can be ‘electronically’ rotated
using the CF command. The declination angle function normally used in conjunction with the compass function
can be used to realign the datum position anywhere in the range 0-359.9°.
See Section 7.4.6 for further details.
2.5 Compass & Declination Angle Operation
The FT742-SM is fitted with a solid-state electronic compass so that the wind direction can be measured relative
to magnetic North. The wind direction can be measured either relative to magnetic North, or by programming the
sensor with the geographical location declination angle, relative to true North. The compass function can also be
disabled if required so that the wind direction is measured relative to the datum mark on the wind sensor body (as
per Figure 4). The compass heading can also be read back at any time using the CF command. See Section 7.4.6
for full details of the CF command. Both the Polar format (P) and NMEA 0183 format (N) outputs provide wind
direction data relative to North (if the compass function is enabled). The NMEA 0183 message also has a field
that indicates whether the compass module is enabled or disabled.
The effects of fixed local magnetic fields (i.e. those caused by magnetised ferrous material close to the compass)
can be compensated for by performing an in situ compass calibration. It is important that the calibration is
performed with the FT742-SM mounted in its final position within the host system. The calibration can only
compensate for fixed magnetic fields generated by the host system. Varying fields caused, for example, by ferrous
objects passing near the FT742-SM (say by a car or truck) or high current electric circuits will not be corrected.
Should the magnetic signature of the host system change significantly (because component parts have been
added or removed), then a recalibration may be required.
2.5.1 Compass Calibration
Compass calibration should be performed away from any external stray magnetic fields. To calibrate the FT742-
SM compass proceed as follows:
1) Mount the FT742-SM in its final position within the host system
2) Ensure the compass is enabled (send the CFE ‘enable compass’ command, see Section 7.4.6).
3) Send the CFC ‘enable calibration’ command (see Section 7.4.6). Important: No further commands should be
sent to the FT742-SM after the CFC command has been sent.
4) Slowly rotate the host system 1 complete revolution in the horizontal plane. The revolution should take between
40 and 60 seconds.
5) To complete the calibration send the CFE ‘enable compass’ command (see Section 7.4.6).
6) Store the new calibration Parameters in the compass module using the CFMS command. The save command,
for example $01,CFMS*//<cr><lf>, will save the new compass calibration parameters calculated during the
calibration process to the Interface Board Flash memory. This command is required.
2.6 Selective Filter Scheme
In addition to the averaging filter described in Section 2.3, the sensor has a feature called the Selective Filter. The
scheme allows the user to set a “validity period”, during which the sensor will exclude invalid readings from
entering the averaging filter. The output will freeze on the last previous “good” reading and only raise an error flag
once the number of bad readings exceeds the validity period. This scheme can be enabled by factory configuration
or by using the FL command (see Section 7.4.14). The filter is turned off by default to match legacy behaviour.
2.7 Error Detection
The sensor has a self-checking mechanism which can detect if a reading is invalid. On very rare occasions where
an invalid reading may have been detected, this is signalled to the computer or data logger by setting an error
flag character within the wind velocity output message (see Sections 7.4.29 and 7.4.30).
When an error is detected, the error flag character is set to a value of: 1.

Section 2 Functional Description
12 FT742-SM (RS422 & RS485) Sensors –User Manual
Note: An optional Overspeed Warning Scheme can be enabled (but is disabled by default). See Section 2.8 for
further details.
It is important that error flags are not ignored. Data associated with an error flag should not be processed as valid
wind data. The system should be capable of riding through rare periods when data may be temporarily unavailable.
If errors are ongoing (more than several seconds), a reset of the sensor should be applied (see Section 7.4.20 for
instructions on sending an RSU command).
It is recommended that errors are monitored and logged. If the frequency of errors has recently increased, then
inspection of the sensor for physical blockages may be required (see Section 4.1).
2.8 Overspeed Warning Scheme
During periods where the sensor detects wind speed beyond the rating of the sensor, the sensor will (by default)
indicate a general error flag status.
An additional overspeed warning scheme can be enabled: if an overspeed condition is detected (above the highest
speed rating), the error flag character will be set to: 2 (see Sections 7.4.29 and 7.4.30) unless a general error
condition is also detected and the flag will be set to 1.
To comply with legacy behaviour, this scheme is disabled by default.
The Overspeed Warning Scheme can be enabled by software commands (see Section 7.4.19), via the Acu Vis
PC software program or enabled in the factory before despatch.
2.9 Heater Setup
The sensor is fitted with an integral two-element distributed heater that can be used to prevent icing-up of the
sensor in freezing temperatures. The heater is controlled automatically by the sensor using a user programmable
‘set point’ temperature. The sensor uses a control scheme which dynamically changes the current supplied to
each individual heater element in order to maintain the programmed set point temperature.
It is important to consider the resistive losses in the cable and rate the cable appropriately. In general, power
losses in the cable should be minimised in order to maximise the available heating power to the sensor. A heater
setpoint temperature of >30°C is recommended for most applications. To change the heater set point or to disable
the heater use the Acu-Vis test software or the HT software command (see Section 7.4.15).
Since the heater circuit is thermostatically controlled, the actual power being drawn from the supply will depend
on the voltage supplied, the programmed set-point and the environmental conditions (i.e. ambient temperature,
wind speed, precipitation etc.). The maximum current that the sensor can consume is limited to 2A (nominal) by
default. The power supply must be rated to provide the maximum heater power (60W @ 30V and 2A) that the
sensor can consume. The heater requires a minimum of 9VDC for operation (contact FT technologies for further
details on the minimum heater voltage limit).
For applications requiring higher power/current ratings or modification of heater performance (including cold
environment operation) please contact the FT technical support teams for further information.
Caution - Modifications to the heater current limit are not permitted on the FT742-SM. Cables must be
suitably rated for the application. Contact FT Technologies for further information.
If the sensor is powered up and there is a possibility it has become iced, it is recommended that the sensor is
allowed to heat up for 30 minutes, followed by a User Reset Command (see Section 7.4.20) to permit the sensor
to initialise correctly without ice blockage.
2.10 Low Power Operation
The sensor is designed for typical operation at 24VDC, operating at a range of 6-30VDC, however the heater will
deactivate below 9VDC. Lower voltages reduce the overall power consumption and heater performance.
For further advice on power and heater management strategies, see Sections 7.4.15 and 7.4.16.

Section 2 Functional Description
13 FT742-SM (RS422 & RS485) Sensors –User Manual
2.11 Acoustic Temperature
The Acoustic Temperature feature takes a measurement of the ambient temperature via measurable acoustic
properties of the airflow. Sections 7.4.2 to 7.4.4 describe related software commands.
Averaged data should be used. The averaging system can be performed for 0 to 50 seconds (in increments of 10
seconds), or between 1 to 10 minutes (in increments of 1 minute).
See Section 2.1 for details regarding operating specifications. Operation with high temperature gradients
(between sensor body and ambient airflow), extreme humidity levels and low wind conditions (below 5m/s) may
result in reduced accuracy.
Software version V7.5.1 introduced the DFC mode (combined data format) that includes AT Temperature data
within the CU data output and WV Query commands. See Sections 7.4.7, 7.4.8 and 7.4.29 for further information.
Caution: The acoustic temperature feature requires calibration at FT Technologies. If the sensor has had
a software upgrade to 7.5 (or above) then the data will be uncalibrated and may not comply with the official
specification. Testing is recommended to confirm suitability for the application.

Section 3 Mechanical & Electrical Installation
14 FT742-SM (RS422 & RS485) Sensors –User Manual
3 MECHANICAL & ELECTRICAL INSTALLATION
The FT742-SM has a surface-mounted design for installation on flat surfaces. The product range is optimised for
cost-efficient operation including the use of standard off-the-shelf cables.
The sensor uses an 8-way M12 connector. IP66 and IP67 ratings are achieved through the use of a compression
fit O-ring seal.
Ensure the airflow into the sensor is not obstructed or influenced by nearby objects.
•See safety instruction requirements on pages 5 and 6.
•The wind sensor installation must be properly designed to ensure the correct
operation of the sensor. This section is for guidance only. It is the responsibility of
the designer and installer to ensure that the installation and its design is fit for
purpose. Please see Disclaimer Section 1.4.
3.1 FT742-SM Sensors
3.1.1 Mechanical & Electrical Integration
The sensor measures the effects of airflow through the sensor cavity on a resonating acoustic signal. The sensor
can be rotated to ensure alignment with a standard reference, typically Magnetic North, or the integrated compass
can calculate this automatically.
Figure 3: The FT742-SM Sensor
The mounting surface should be smooth and flat. Textured, uneven or damaged surfaces will reduce the quality
of the water ingress protection. For a typical metallic mounting surface, a fixing torque of 1.4Nm and 3-4mm of
thread engagement should be enough to adequately compress the O-ring seal.

Section 3 Mechanical & Electrical Installation
15 FT742-SM (RS422 & RS485) Sensors –User Manual

Section 3 Mechanical & Electrical Installation
16 FT742-SM (RS422 & RS485) Sensors –User Manual
Figure 4: Outline Dimensions, Assembly & Wind Direction Reference (Compass Disabled)
Figure 5: Sensor Base Dimensions
Figure 5 displays the location of the O-ring groove (FT O-ring part number FT029, manufacturer part number:
2-127 O-Ring EPDM 70 Shore). One O-ring is supplied with new sensors. The use of lubricant on the O-ring will
depend on the material selection. The breather hole allows the air pressure within the sensor to balance during
varying environmental conditions, it is important the breather hole is not sealed and mounting designs permit a
small amount of air movement around the breather hole.

Section 3 Mechanical & Electrical Installation
17 FT742-SM (RS422 & RS485) Sensors –User Manual
The O-ring compression fit is secured using 5x M3 fixings. The internal thread depth is 4.5mm, the length of fixings
should be determined considering the thickness of the mounting surface. Regular condition monitoring of the
sealing interface is recommended.
Caution –Excessive length or tightening of the M3 screw may cause damage to the sensor threads.
3.1.2 Connector Details
All electrical connections are made to the digital sensor via an 8-way multi-pole connector located in the base of
the wind sensor housing. The connector pin designations are shown in Figure 6. The connector conforms to IEC
61076-2-101.
Pin
RS422
RS485
FT009 Wire Colour*
1
0V
0V
Brown
2
6-30VDC
6-30VDC
White
3
TX Data A -
N/C
Blue
4
RX Data A -
Data A -
Black
5
TX Data B +
N/C
Grey
6
RX Data B +
Data B +
Pink
7
N/C
N/C
Violet
8
N/C
N/C
Orange
The FT009 cable includes shielding
*Caution: Wire colours apply only to FT supplied FT009 cables.
Other cables may use different colour schemes, contact FT
technologies for further information.
Figure 6: Sensor Connector Pin
The FT742-SM sensor uses a M12 8-way male connector (ERNI Production GmbH, part number 464676).
Finished cable assemblies are available off-the-shelf as well as custom manufacture. The FT742-SM can use up
to 2A with the heater enabled, it is necessary to confirm all cables used are suitably rated for the operational
environment.
Care must be taken to ensure that the cable is suitable for the environment it will be used in and is adequately
rated and approved, for example AWM Style 21198. In an area with a moderate or severe lightning strike exposure
the cable may not provide sufficient EMI protection. In this case the cable will require further shielding, for example
being enclosed in a grounded metal pipe or conduit, or the use of sensors with a higher grade of protection (for
example the FT742-PM range).
The part FT009 is a 1.5m cable that can be used with the FT742-SM. This cable is included with sensors for
datalogging purposes (RS part 892-0498, TE Connectivity part 2273049-1, available in 1.5 to 10.0m lengths).
Acu-Test USB test cables are purchased separately.
3.1.3 Lightning, Surge & EMI Protection
It is important to install the sensor and cabling with appropriate protection against lightning and other sources of
electromagnetic interference, in order to maximise its chance of survival and continued operation during and after
exposure.
The FT742-SM sensor is specifically designed for meteorological applications where the risk of lightning exposure
(indirect) is low.
All connections from the wind sensor to any data acquisition equipment and power supply should run through
suitable Surge Protection Devices (SPDs). This will suppress any unwanted overvoltage transients present on the
signal or power lines. The surge suppression devices should conform to an appropriate standard (for example UL
1449 listed).
For areas where there is a high risk of lightning exposure (but still indirect) we would recommend the use of the
Pipe-Mount (PM) range of sensors. In such applications, the sensor body should be well grounded and the PM

Section 3 Mechanical & Electrical Installation
18 FT742-SM (RS422 & RS485) Sensors –User Manual
variant of sensor is a more suitable solution. See the PM wind sensor User Manual for more details on this or
contact FT Technologies for more information.
Advanced surge and lightning protection typically requires a grounded lightning mast, SPDs, grounded metallic
conduit and 360°-terminated EMC cable glands.
Data integrity can be improved by using grounded metallic conduit for EMC protection. Checksum validation and
filtering of corrupted data is recommended.

Section 4 Service, Configuration & Testing
19 FT742-SM (RS422 & RS485) Sensors –User Manual
4 SERVICE, CONFIGURATION & TESTING
4.1 Inspection
The following checks are required to identify any signs of corrosion or damage on the sensor which may hinder
its performance. It is recommended that these checks be carried out annually.
Mechanical damage: Check the sensor body for signs of damage, paying particular attention to the seals. Also
inspect for signs of lightning damage which may appear as burns or scorch marks (or burnt smells). If damage
has occurred replace the sensor immediately. Inspect the hydrophobic cavity coating for wear, corrosion and
damage. Check the O-ring seal and fixings are in good condition, replace them if necessary for long-term
protection.
Corrosion: Inspect the mounting surfaces of the sensor for signs of corrosion. If corrosion is present on any
surface, it should be removed using an abrasive cloth. Check that any fixings and O-rings are in good condition
with no signs of corrosion and tighten as necessary. If corrosion is present replace with parts of the appropriate
finish (see Section 3).
Interconnection cable: Inspect the condition of the cable. If it has become frayed or damaged it should be
replaced. Intermittent cable faults may not be visible and may show up as data errors. Check the intended network
component values (termination resistors etc.).
Connector protective sleeve: If cable protection is used, check for any signs of damage or degradation.
Cleaning: The measurement cavity has a special hydrophobic coating (water repelling) which helps to prevent
water building up. When water enters the measurement cavity the surface helps to wash away dust and debris
which may have settled. If any debris is present this can be removed by gently rinsing the measurement cavity
surface with distilled water using a laboratory wash bottle or similar. Please note excess water droplets can be
removed by lightly blowing or shaking the sensor.

Section 4 Service, Configuration & Testing
20 FT742-SM (RS422 & RS485) Sensors –User Manual
Do not scrape or scratch the surfaces whilst rinsing. Under no circumstances should objects be inserted inside
the measurement cavity, as this can cause irreparable damage. If the coating has been damaged, then it may
need to be reapplied. The body of the sensor can be washed if required using the same method as described
above. Whilst washing the sensor care must be taken not to get water in the breather hole or into the connector
at the base of the sensor.
Do not use cleaning chemicals to clean the sensor. If washing a nearby item protect the sensor with a suitable
cover. Ensure the cover is removed before re-enabling the wind data survey.
4.2 Fault Finding & Troubleshooting
To determine whether a sensor has a fault carry out the following steps:
•Follow the inspection procedure above to identify signs of physical damage.
•Remove any objects or insects lining the cavity or blocking the airflow.
•Reset the sensor (RSU command or power-cycle).
If there are signs of physical damage and/or the sensor is failing to communicate properly, it should be replaced.
Sensors may be returned to FT Technologies for further analysis if required (see Section 4.3).
Warning –The sensor contains no user serviceable components. Do not attempt
disassembly as damage may result and product warranties will be invalidated.
During extreme weather conditions there may be periods where data is temporarily unavailable. However there
are ways to mitigate against these affects. The following steps should be taken to ensure the highest levels of
data availability from the sensor:
•Check that the wind sensor data and status flag errors are being processed as per the advice in Sections
7.4.29 and 7.4.30.
•Ensure that any installed lightning and EMI protection (see Section 3) is in good condition and any cable
shielding is terminated at both ends. All mating surfaces must be free of paint and corrosion.
•Check that the measurement cavity’s special coating is in a satisfactory condition and no debris is present.
Debris can be blown out or washed out with distilled water spray.
Please contact FT Technologies for further information and advice if required.
4.3 Returns
If a sensor appears to be faulty, compile a detailed fault description for each sensor, then contact FT Technologies
to request a Returns Materials Authorisation (RMA) form. Please complete the form and return as instructed.
Returns cannot be accepted without prior approval via this authorisation form.
Units damaged by lightning or disassembled by the customer cannot typically be repaired, however an
inspection fee may still apply.