FT Technologies FT702LT/D User manual

1 FT702LT/D Flat Front Wind Sensor 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]
A4239-6-EN
July 2017
The FT and Acu-Res logos are registered trademarks of FT Technologies Ltd
FT702LT/D Wind Sensor Manual
Analogue Flat Front Variant

2FT702LT/D Flat Front Wind Sensor Manual
Contents
Safety Instructions ....................................................................................................4
1INTRODUCTION .................................................................................................6
1.1 Product Overview ............................................................................................................ 6
1.1 Build Versions and Labelling.......................................................................................... 7
1.2 Pipe Mount Sensor .......................................................................................................... 7
1.3 Scope of Use.................................................................................................................... 7
1.4 Disclaimer........................................................................................................................ 8
2FUNCTIONAL DESCRIPTION............................................................................9
2.1 Technical Performance.................................................................................................... 9
2.2 Current Loops.................................................................................................................10
2.2.1 Current Loop Characteristics........................................................................................10
2.2.2 Wind Speed Loop.........................................................................................................10
2.2.3 Wind Direction Loop.....................................................................................................12
2.2.4 Changing the wind datum direction...............................................................................12
2.2.5 Error Detection.............................................................................................................13
2.3 Heater Setup ...................................................................................................................13
3INSTALLATION ................................................................................................14
3.1 Connectivity....................................................................................................................14
3.1.1 Connector Details.........................................................................................................14
3.1.2 Cable Details................................................................................................................14
3.2 Mounting the FT702LT/D ................................................................................................15
3.2.1 Alignment.....................................................................................................................16
3.3 Lightning protection and EMC .......................................................................................17
4.3.1 Protection against direct lightning effects......................................................................17
4.3.2 Protection against indirect lightning effects and electromagnetic interference................19
4.3.3 Surge protection...........................................................................................................19
3.4 Inspection of the FT702LT/D ..........................................................................................21
3.5 Fault Finding & Troubleshooting ...................................................................................22
3.6 Returns............................................................................................................................22
4EVALUATION ...................................................................................................23
4.1 Evaluation Pack..............................................................................................................23
4.2 Wiring Diagrams.............................................................................................................23
4.3 Quick Start Steps............................................................................................................24
5CHANGING SETTINGS ....................................................................................25
5.1 Installing the Configuration Program.............................................................................25
5.2 Configuring the FT702LT/D ............................................................................................25
5.3 Change Settings .............................................................................................................26
5.4 Sensor Report.................................................................................................................26
5.5 Current Loop Test...........................................................................................................27
5.6 Reading the Wind Data...................................................................................................28
5.7 Wind Sensor Mode Warning...........................................................................................28

3FT702LT/D Flat Front Wind Sensor Manual
Product Symbols
The following symbols are used upon the product and throughout the manual.
Meaning / Description
Symbol
Significantion/ Description
Warning/ Caution
An appropriate safety instruction should be
followed or caution to a potential hazard
exists
Advertisement
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
L'équipement fonctionne sous une
alimentation en courant continu (CC)
uniquement.
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
or landfill.
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.
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.
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.

4FT702LT/D Flat Front Wind Sensor 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 remain compliant with the electrical safety requirements of the UL / CSA
61010-1 standards, the equipment must be;
oConnected to an appropriately approved isolated power supply (for example UL/CSA IEC
60950-1:2005 + A1:2009 + A2:2013) rated 20-30VDC and be current limited (6A Max)
oProtected by UL 1449 Listed surge protective 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.

5FT702LT/D Flat Front Wind Sensor 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 convenablement isolée (par exemple UL/CSA IEC 60950-
1:2005 + A1:2009 + A2:2013) de tension nominale 20-30 VCC et avec courant limité (6 A
max).
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
6 FT702LT/D Flat Front Wind Sensor Manual
1 INTRODUCTION
1.1 Product Overview
The FT702LT/D is a solid-state ultrasonic wind sensor which uses a patented Acoustic Resonance airflow
sensing technique to measure accurately both wind speed and direction. The FT702LT/D has been specifically
designed to operate in harsh environments such as offshore and lightning and ice-prone areas. The wind sensor
has no moving parts to degrade or wear-out and is designed for applications requiring high reliability. The
FT702LT/D helps reduce costly down-time and unscheduled maintenance visits.
Mounting and aligning the sensor is very straightforward. The mounting flat on the sensor body defines the 0O
wind datum so that the sensor automatically aligns to a reference point. For operation in ice-prone areas the
FT702LT/D is fitted with a highly effective thermostatically controlled ‘all-body’ heating system. A three element
heater (one element located in the top of the sensor and two in the bottom) is used to ensure that heat is evenly
distributed over the entire surface area.
Figure 1: FT702LT/D Flat Front Wind Sensor#
#actual sensor shape varies between build versions
Maximum Sensor
Dimensions
h (mm)
w (mm)
Before build version 22
167
50
Build versions 22 and after
161
55

Section 1 Introduction
7 FT702LT/D Flat Front Wind Sensor Manual
1.2 Build Versions and Labelling
Each time a substantial revision is made to the design of the wind sensor the build version number is
incremented. All new variants are backwards compatible with the previous build versions. Each uses the same
mounting, connector pin outs and signal characteristics and contains all the original functions.
Where a new function has been introduced the first build version to have it included is stated.
Figure 2 shows examples of how to identify an FT702LT’s build version, individual serial number and wind
speed scaling (if applicable), depending on which main label is attached. Section 2.2.2 describes how you can
use the wind speed scaling reference to identify the calibration of the sensor.
Serial number
Build version
Wind speed scaling reference
Product label key*
*Additional labels may also be attached. Examples of older labels are included for reference.
Figure 2: Examples of Main Sensor Labels
Only sensors marked with the Intertek label conform to UL 61010-1 and are certified to CAN/CSAC22.2 No.
61010-1-04. Some early build versions do not have this certification.
1.3 Pipe Mount Sensor
It is possible to mount the wind sensor directly on top of a pipe. Details of the Pipe Mount sensor and system
can be found in a separate manual. The Pipe Mount sensor offers enhanced environmental sealing, lightning
protection, thermal conductivity and corrosion resistance. The base of the Pipe Mount sensor is different to the
Flat Front sensor’s described in this manual. Please contact FT Technologies for further information.
1.4 Scope of Use
The FT702LT/D is designed, manufactured and optimised for high availability. The FT702LT/D wind sensor
often attains 99.9% or better availability of wind speed and wind direction readings.
No promise in part or full can be given to guarantee an FT702LT/D wind 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

Section 1 Introduction
8 FT702LT/D Flat Front Wind Sensor Manual
Poor quality electrical connections
Lightning exposure
Problematic environmental conditions or combination of conditions
Typically higher levels of wind speed and wind direction data availability are achieved through the use of an
additional FT sensor or an additional mechanical or ultrasonic sensor. Control strategies or controller
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.
1.5 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 direct 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 FT702LT/D Flat Front Wind Sensor Manual
2 FUNCTIONAL DESCRIPTION
2.1 Technical Performance
Sensor Performance1
Measurement Principle Acoustic Resonance, compensated against variations in temperature,
pressure and humidity
Wind speed Measurement
Range 0-50m/s
Accuracy 0.5m/s (0-15m/s), 4% (>15m/s)
Resolution 0.1m/s
Wind Direction Measurement
Range 0 to 360
Accuracy 2(within 10of 0datum), 4(beyond ±10⁰of 0⁰datum)
Resolution 1
Environment
Temperature Range -40to +85C (operating and storage)
Humidity 0-100%
Data I/O
Analogue Option
Interface 4-20mA, galvanically isolated from power supply lines and case
Format One 4-20mA current loop for wind speed (see Figure 4 for scaling factors
available)
One 4-20mA current loop for wind direction (4-20mA = 0-360deg) (see
Figure 8 for offset options available)
Reading Update Rate 5 per second
4-20mA Configuration Port2RS485 half duplex, non-isolated relative to power ground
Power Requirements4
Supply Voltage 20V to 30V DC (24V DC nominal)
Supply Current (Heater off) 30mA
Supply Current (Heater on) 6A (max)* –The heater is thermostatically controlled. Heater power
consumption will depend on the heater energy required to keep the sensor’s
temperature at a user determined set point. The heater and sensor power
consumption is limited by default to 99W3.
*Only 4A (max) power consumption possible for sensors prior to build
version 223.
Physical
Weight 320g (max)
Material Aluminium alloy, hard anodised
I/O Connector 8 way (Analogue option),
Mounting Method Self aligning, single screw fixing
Notes:
1.All specifications subject to change without notice
2.The Configuration Port is provided to allow the user to change the internal settings of the FT702LT/D and to
perform diagnostic testing. This interface should only be used for configuration and test purposes. This
interface is not intended for permanent connection to the turbine controller.
3.The heater set point and current limit can be configured by programming the sensor’s internal parameter
settings (only available from build version 22 and above)
4.See safety instruction requirements (page 4)

Section 2 Functional Description
10 FT702LT/D Flat Front Wind Sensor Manual
2.2 Current Loops
2.2.1 Current Loop Characteristics
The FT702LT/D wind sensor incorporates two galvanically isolated 4-20mA current loop outputs, one loop for
wind speed and one loop for wind direction. These current loop outputs can be converted into measurable
output voltages with the addition of external resistors.
Each loop should be powered from a DC supply in the range 20V to 30V. A positive supply must be provided to
one of the current loop wires.The other wire must then be connected through a current meter to ground. This is
because the FT702LT/D current loops sink current, they do not source it. A common supply can be used if
required. Loop connections are polarity insensitive so that the +ve or –ve loop supply connection can be made
to either of the current loop connection pins. See example wiring in Figure 21.
The current loops are able to operate over long cable distances; however the overall loop resistance should not
exceed the values given in Figure 3. It is recommended that twisted pair interconnection cabling should be
used. The cable should also include an overall braided screen.
Loop Supply
Maximum Loop Resistance
20V
500 Ω
24V
700 Ω
30V
1000 Ω
Figure 3: Maximum Current Loop Resistance
The wind sensor’s current loop outputs are updated at a rate of 5 times per second. An average of several
readings should always be used for any calculations or control decisions because single readings can
accidentally become corrupted (see section 2.2.5).
The sensor has its own internal filtering enabled by default, which dampens the speed and wind direction
outputs by averaging the previous 1.6 seconds of data. It is possible to disabled the internal filter (however not
recommended) by using the FT702LT/D Set-Up and Test Program (See Section 4 and 5).
2.2.2 Wind Speed Loop
The default wind speed scaling is such that a change from 4 to 20mA represents 0m/s-50m/s. This corresponds
to a scaling factor of 0.32mA per m/s. The measurement scaling factor for the wind speed current loop is set at
the factory. Figure 4 shows the wind speed calibrations that are available.
The models with scaling factors above 50m/s are intended for applications such as wind turbine controllers
where the wind speed scaling is preset and cannot easily be changed. Because the maximum wind speed
range of the FT702LT/D is 50m/s for models with full scale settings above 50m/s the maximum output current is
limited to a value equivalent to 50m/s (see Figure 4).
Wind Speed Scaling references
4mA
20mA
Scaling Factor (mA per m/s)
30
0m/s
30m/s
0.5333
40
0m/s
40m/s
0.4000
50
0m/s
50m/s
0.3200
60
0m/s
60m/s
0.2666
output limited to 17.33mA (50m/s)
70
0m/s
70m/s
0.2286
output limited to 15.43mA (50m/s)
Custom
0m/s
XX
Variable
Only available from build version 22
Figure 4: Wind Speed Scaling Factors
From build version 22 the wind speed loop can also be calibrated with non-linear scaling functions. See
example customisable calibration in Figure 5.

Section 2 Functional Description
11 FT702LT/D Flat Front Wind Sensor Manual
Figure 5: Wind speed output calibrations
If a wind sensor is replaced care must be taken to ensure that the 2 sensors have the same
calibration. Otherwise the system processing the wind data might perform differently after the
sensors are swapped
The wind speed scaling reference given on the main product labels can be used to identify the wind speed
calibration of the sensor. (See section 1.2).
From build version 22 and above a C:Code label might be attached. The C:Code number then indicates the type
of calibration applied. 2 examples are shown in Figure 6.
V20 - Standard 0-50m/s = 4-20mA. = Default
V22 - All other calibrations
The wind speed scaling reference is shown on
the part number label as 50
The C-Code:01 label is sometimes also
attached
No wind speed scaling reference is shown
on the part number label
The additional C-Code label and number
XX is used to identify the type of
calibration applied
Figure 6: Build version 22 sensor calibration label examples
0
4
8
12
16
20
24
010 20 30 40 50 60 70
Current Loop Output (mA)
Wind Speed (m/s)
Wind Speed Current Loop Output Calibration Examples
0-40 m/s
0-50 m/s = Factory Default
0-60 m/s
Customisable calibration
Only from build version 22

Section 2 Functional Description
12 FT702LT/D Flat Front Wind Sensor Manual
2.2.3 Wind Direction Loop
The wind direction scaling is such that a change from 4 to 20mA represents 360 degrees (with no dead band)
which corresponds to a scaling factor of 0.0444mA per degree.
The FT702LT/D measures the wind direction relative to the 0 degree datum. The 0 degrees datum location for
the FT702LT/D is shown in Figure 7.
The default setting for the current loop output when the wind is blowing towards the datum direction is 12mA. If
required, the direction loop can be set to give an output of 4mA at the datum direction. The output options are
shown in Figure 8.
Figure 7: Visualisation of direction with 4mA and 12mA current offsets
Figure 8: Comparison of wind direction current offsets
When operating in the 4mA datum current mode there is a 16mA transition each time the wind direction crosses
the datum. In the 12mA datum current mode the output current varies linearly about the 12mA value as the wind
direction moves around the datum.
2.2.4 Changing the wind datum direction
The datum direction can be electronically rotated (either clockwise or counter clockwise) in 1 deg increments
using the FT702LT/D Set Up and Test Program (see section 5) to apply this adjustment. Once the datum offset
has been set it will be retained in the FT702LT/D Flash memory.
180 225 270 315 0 45 90 135 180

Section 2 Functional Description
13 FT702LT/D Flat Front Wind Sensor Manual
2.2.5 Error Detection
If the FT702LT/D detects that a reading may be invalid this is signalled to the controller or data logger by setting
the current of both loops to a value of 1.4mA by default. The error current level can be configured (see Section 5)
by the user from 1.4mA up to 3.9mA in steps of 0.1mA (only available from build version 22 and above).
The error condition must occur for more than 1 second for the current loops to be set to this condition. If an error
occurs for less than 1 second then the loop outputs will be held at the last valid reading for the duration of the
error.
Figure 9: 4-20mA valid readings range
Always use an average of several readings for any calculations or control decisions because
single readings can accidentally become corrupted.
The data acquisition system needs to not only sample the 4-20mA measurement range, but also should include
logic to process and exclude data if it is outside the measurement range. The data acquisition system should
distinguish between a status flag error sent by the wind sensor and other out of range readings in order to help
diagnose if a fault has occurred with the power supply, cable or wind sensor.
2.3 Heater Setup
The FT702LT/D is fitted with an integral three element distributed heater that can be used to prevent icing-up of
the sensor in freezing temperatures. The heater is controlled automatically by the FT702LT/D using a user
programmable ‘set point’ temperature. The FT702LT/D uses a control scheme which dynamically changes the
current supplied to each individual heater 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.
The factory default setting for the heater set point value is 30°C. This is the recommended setting for most
applications. To change the heater set point or to disable the heater use the FT702LT/D Set Up and Test
Program (see section 5).
Since the heater circuit is thermostatically controlled the actual power being drawn from the supply will depend
on the programmed set point and the prevailing environmental conditions (i.e. ambient temperature, wind
speed, precipitation etc). The maximum power that the FT702LT/D heater and sensor can consume is by
default limited to 99W. The power supply must be rated to provide the maximum power that the sensor can
consume.
From build version 22 and above the maximum current limit of the sensor can be adjusted in software from 0.1 –
6 Amps. To change the current limit use the FT702LT/D Set Up and Test Program (see section 5).
From build version 22 and above the sensor can detect when the supply voltage drops below 9 VDC, when this
occurs the heaters are automatically switched off.

Section 3 Installation
14 FT702LT/D Flat Front Wind Sensor Manual
3 INSTALLATION
See safety instruction requirements on page 4.
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 1.5.
3.1 Connectivity
3.1.1 Connector Details
All electrical connections are made to the FT702LT/D via an 8-way multipole connector located in the base of
the wind sensor housing. The wind sensor connector pin designations are shown in Figure 10 and the mating
connector manufacturer’s part numbers in Figure 11.
Figure 10: Sensor connector pin out
Connector Type
Connector
Description
Manufacturers Part Number
FT Sensor
Type
Maximum Outer
Cable Diameter
Manufacturer
FT702LT/D
Cable Side
Connector
8 way plug
SS104Z129-1
FT702LT/D
Analogue
Option
8.0mm
W.W.Fischer
FT702LT/D
Cable Side
Connector
8 way plug
SX2F1C-P08NJH9-0001
FT702LT/D
Analogue
Option
9.2mm
ODU
Figure 11: Cable Connector Sourcing Options
3.1.2 Cable Details
The mating connectors for the FT702LT/D are suitable for use with cables with overall diameters of up to 9mm
and for individual cores of diameters of up to 1.2mm. Cable such as SD980CPTP 3x2x0.5mm2 from SAB
Brockskes or similar types may be used. Care must be taken to ensure that the cable is suitable for the
environment it will be used in and is adequately approved, for example AWM Style 21198.
In an area with a moderate or severe lightning strike exposure the cable shield will not provide sufficient
protection. In this case the cable will require further shielding such as being enclosed in a metal pipe or conduit
(see section 3.3).

Section 3 Installation
15 FT702LT/D Flat Front Wind Sensor Manual
3.2 Mounting the FT702LT/D
The FT702LT/D is designed to be mounted using an M6 socket head cap screw, nut and washer. The mounting
flat on the support tube of the sensor (see Figure 1) allows for firm fitting against a flat surface. The preferred
finish of the screw, nut, washer and the mounting bar is hot dipped galvanised steel. The mounting bar should
have a minimum galvanising thickness of 50µm to ensure long-term protection against corrosion. The
galvanising quality should conform to ASTM A123, Standard Specification for Zinc (Hot-Dip Galvanised)
Coatings on Iron & Steel Products. Aluminium components of the appropriate grade could be used as an
alternative.
The mounting flat is provided free of coatings to allow for a good electrical connection between the body of the
sensor and ground through the mounting bar. In order to protect the mounting flat against corrosion, a very thin
layer (<0.2mm) of electrical joint compound should be applied. An example of this could be AFL Global’s
Electrical Joint Compound # 2. It should be applied directly to the sensor’s mounting flat, whilst avoiding the
fixing hole. Use of an electrical joint compound will also help to maintain long-term low impedance connection to
ground. This connection should be checked as part of the annual inspection of the sensor as detailed in Section
3.4.
Some electrical joint compounds contain fluoride etchants which may react with certain materials. Material
compatibility should therefore be checked prior to application (refer to the electrical joint compound
manufacturer’s data).
In order to keep the pressure within the sensor equalised with the atmospheric pressure, a small breather hole
is located within its support tube. It is therefore important that the airway to this breather hole be kept clear. This
can be achievable by cutting a small 3mm channel in the mounting bar as shown (see Figure 12).
Figure 12: Sensor Installation
It is recommended that a protective sleeve be fitted over the base of the sensor and the connector. This will
provide environmental protection as well as stress-relief from vibration. Heat shrink or cold shrink would be
suitable for this purpose. FT offer a cold shrink solution which is available on request (part number FT909). The
sleeve should cover the lower part of the support tube; the connector itself and at least 25mm of cable (see
Figure 13).

Section 3 Installation
16 FT702LT/D Flat Front Wind Sensor Manual
Figure 13: FT702LT/D-FF with protective sleeve
3.2.1 Alignment
The FT702LT/D measures the wind direction relative to the mounting flat and bar. When the wind sensor is
correctly aligned the wind direction measurements will be as shown in Figure 14.
Figure 14: Correct Sensor Alignment

Section 3 Installation
17 FT702LT/D Flat Front Wind Sensor Manual
3.3 Lightning protection and EMC
It is important to install the sensor 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.
3.3.1 Protection against direct lightning effects
The sensor installation must be designed in such a way that a protection zone is created around the sensor so
that its body can never be subjected to a direct lightning strike.
Figure 15: Direct lightning strike
Figure 16: Indirect lightning strike
This level of protection is achievable through the use of conductive structural parts known as “lightning
interceptors”. These help to create the protection zone and to divert the majority of the lightning current away to
ground.
The lightning interceptor must have a direct connection to ground through metal parts with a minimum cross-
sectional area of 50mm2(see Figure 19). The length of any grounding wire or strap must be kept to a minimum.
This will help to provide the lowest possible impedance path to the ground reference.

Section 3 Installation
18 FT702LT/D Flat Front Wind Sensor Manual
Figure 17 below shows examples of lightning interceptors* and how they can be used to create a protection
zone around the sensor. It is recommended that the interceptor is made from hot dipped galvanised steel or
aluminium in order to prevent corrosion. This will ensure a long-term low impedance connection to ground.
Figure 17: Ring and Rod interceptors
*The standards for Lightning Protection of Wind Turbines are described in IEC 61400-24. The installation
instructions in this manual should be sufficient to ensure that the lightning protection zone around the sensor will
achieve a lightning protection level of LPZ0B as described in the standard.

Section 3 Installation
19 FT702LT/D Flat Front Wind Sensor Manual
3.3.2 Protection against indirect lightning effects and electromagnetic interference
Objects within the protection zone described above can still be subject to very high electromagnetic field and
partial lightning surge currents. It is therefore critical that appropriate shielding and termination is used
throughout the system to reduce these effects. A shielded signal cable will offer some protection however it is
recommended that double shielding is employed between the sensor and the chassis of the data acquisition
and power supply cabinet.
A metal conduit surrounding the shielded cable is a good way of providing this additional protection and will also
help to prolong the life of cables and connectors. The impedance of this metal conduit needs to be as low as
possible since a substantial proportion of the lightning current will flow in it. An example of metal conduit could
be HellermannTyton’s HelaGuard steel conduit with plastic coating and steel overbraid.
All cable shielding must be continuous and terminated at both ends using EMC glands or cable clamps with a
direct connection to the cabinet chassis. There must also be a direct connection from the cabinet chassis to the
grounding reference. Any metal conduit used must also be continuous and terminated at both ends with
appropriate fittings. Figure 18 below shows the principle of the protection scheme.
①Preferably this
connection is established
using structural steel
parts or alternatively by
use of a copper cable
with a cross section of
min. 50mm2
②Any shielding conduit
must be terminated at
both ends
③Shielded cable must
either be terminated
using an EMC cable
gland in the cabinet wall -
or alternatively using a
cable clamp in direct
connection with the
cabinet chassis
④The chassis of the
cabinet must have a
direct connection to
ground
Figure 18: Protection of equipment against indirect effects
3.3.3 Surge protection
All connections from the wind sensor to any data acquisition equipment and power supply should run through
Surge Protection Devices (SPDs). This will suppress any unwanted overvoltage transients present on the signal
or power lines. The surge suppression devices are to be UL 1449 listed.
The ratings of the SPDs must be suitable for the surge conditions. Assuming that appropriate shielding and
termination has been used throughout, then the SPDs used with our sensor should have a minimum surge
current rating of 20kA (8/20µs) and be capable of clamping the output below the maximum input voltage
accepted by the electronic systems they are connected to. This will prevent any surges or large voltage
differences being present at the inputs to the wind sensor, data acquisition electronics or power supply.

Section 3 Installation
20 FT702LT/D Flat Front Wind Sensor Manual
The SPDs should be installed as close as possible to the point where the signals enter the cabinet in order to
prevent noise propagating to other electronics. The SPDs should also be grounded appropriately. Figure 19
shows how the SPDs should be installed.
Figure 19: FT702LT/D analogue interface surge protection
The supply pair [24VDC / 0VDC] is electrically isolated from the other lines and the chassis. The four current
loop signals are isolated from the power supply lines and the chassis. An example of SPD suitable for this
protection can be sourced from Phoenix Contact as shown in Figure 20 below. Users are responsible for
ensuring the suitability of these components for their application.
Manufacturer
Type
Manufacturers part number
PSU lines
Phoenix Contact
Surge protection plug (x1)
2819008 PT PE/S+1X2-24-ST
Base element (x1)
2856265 PT PE/S+1X2-BE
Current Loop Lines
Phoenix Contact
Surge protection plug (x2)
2856058 PT 1x2-24AC-ST
Base element (x2)
2856113 PT 1x2-BE
Figure 20: Typical SPD configuration used to protect sensor