FT Technologies FT702LT User manual

1FT702LT Flat Front Wind Sensor Manual
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A4206-4-EN
JULY 2017
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FT702LT Wind Sensor Manual
Digital (RS485) - Flat Front Variant

2FT702LT Flat Front Wind Sensor Manual
Contents
Product Symbols....................................................................................................... 3
1INTRODUCTION.................................................................................................. 6
1.1 Product Overview .............................................................................................................6
1.2 Build Versions and Labelling...........................................................................................6
1.3 Pipe Mount Sensor ...........................................................................................................7
1.4 Scope of Use.....................................................................................................................7
1.5 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 Electronic Rotation of the Datum Direction ..................................................................11
2.5 Error Detection................................................................................................................11
2.6 Heater Setup....................................................................................................................11
3INSTALLATION................................................................................................. 12
3.1 Connectivity ....................................................................................................................12
3.2 Description of Parts........................................................................................................14
3.3 Lightning protection and EMC.......................................................................................16
3.4 Inspection of the FT702LT..............................................................................................21
3.5 Fault Finding & Troubleshooting...................................................................................22
3.6 Returns............................................................................................................................22
4EVALUATION.................................................................................................... 23
4.1 Evaluation Pack ..............................................................................................................23
4.2 Acu-Vis Software ............................................................................................................23
4.3 FT054 Evaluation Cable..................................................................................................24
4.4 Quick Start Steps............................................................................................................24
5SENSOR COMMUNICATION............................................................................ 26
5.1 Introduction.....................................................................................................................26
5.2 Configuring the FT702LT................................................................................................26
5.3 Communication...............................................................................................................26
6PARAMETER SETTINGS.................................................................................. 30
6.1 Command Types.............................................................................................................30
6.2 User Calibration Table....................................................................................................32
6.3 Timing Constraints .........................................................................................................33
6.4 Command Parameters....................................................................................................34

3FT702LT Flat Front Wind Sensor Manual
Product Symbols
The following symbols are used upon the product and throughout 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.
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 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 remains 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 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
6FT702LT Flat Front Wind Sensor Manual
1 INTRODUCTION
1.1 Product Overview
The FT702LT 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 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 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 0°wind datum so that the sensor automatically aligns to a reference point. For operation in
ice-prone areas the FT702LT 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 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
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.

Section 1 Introduction
7FT702LT Flat Front Wind Sensor Manual
Figure 2 shows how to identify an FT702LT’s build version and individual serial number, depending on
which main label is attached.
Serial Number
Build version
Product Labels*
*Additional labels may also be attached
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 sensors described in this manual. Please contact FT Technologies
for further information.
1.4 Scope of Use
The FT702LT is designed, manufactured and optimised for high availability. The FT702LT 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 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
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
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.

Section 1 Introduction
8FT702LT Flat Front Wind Sensor Manual
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
9FT702LT 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), -40to +85C (storage)
Humidity 0-100%
Data I/O
RS485 Option
Interface Digital RS485, galvanically isolated from power supply lines and
case
Format ASCII data, polled or continuous output modes
Data Update Rate 5 measurements per second
Power Requirements3
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 99W2.
*Only 4A (max) power consumption possible for sensors prior to build
version 22.
Physical
Weight 320g (max)
Material Aluminium alloy, hard anodised
I/O Connector 5 way (RS485 option),
Mounting Method Self aligning, single screw fixing
Notes:
1.All specifications subject to change without notice
2.The heater set point, current limit and maximum power limits can be configured by programming the
sensor’s internal parameter settings (only available from Version 22 and above)
3.See safety instruction requirements (page 4)

Section 2 Functional Description
10 FT702LT Flat Front Wind Sensor Manual
2.2 Wind Speed Calibration
All FT702LT wind sensors are built and then calibrated in the same wind tunnel before dispatch. There is no
need to recalibrate a sensor over its lifetime as the sensor has no moving parts and so 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 tunnel are designed to give
a calibration profile that is within the accuracy limits set in the product technical specification (see section 2.1).
Every 3 months the accuracy of FT’s wind tunnel is compared with the accuracy of an independent wind tunnel
to ensure that no drift has occurred.
However, in exceptional circumstances users may wish to apply additional calibration factors. Version 22 sensors
and above therefore have an option to set a User Calibration Table, which can modify the wind sensor’s wind
speed output (see section 6.4.19).
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 wind sensor should be fitted.
The FT702LT 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 6.4.8 & 6.4.9).
First Reading Second Reading
Third Reading
Forth Reading -1 -2 -3 -4 -5 -6 -7 -8
Previous Readings
0.0 0.2 0.4 0.6-0.2-0.4-0.6-0.8-1.0-1.2-1.4-1.6
Time (s)
= Sum of 8 Readings /8
= Sum of 8 Readings /8
= Sum of 8 Readings / 8
First Reading Second Reading
Third Reading
Forth Reading -1 -2 -3 -4 -5
Previous Readings
0.0 0.2 0.4 0.6-0.2-0.4-0.6-0.8-1.0
Time (s)
= Sum of 4 Readings /4
= Sum of 4 Readings / 4
= Sum of 4 Readings /4
Filter length 0008 Filter length 0004
Figure 3: Examples of FIR Filtering
Always use an average of several readings for any calculations or control decisions because
single readings can accidentally become corrupted.

Section 2 Functional Description
11 FT702LT Flat Front Wind Sensor Manual
2.4 Electronic Rotation of the Datum Direction
The datum direction of the FT702LT can be offset electronically by using the CF command (Section 6.4.2). This
facility can be used to adjust the datum direction in case of any mechanical misalignment within the mounting
arrangement. To offset the datum direction, in either the clockwise or anticlockwise direction, use the CF
command (Section 6.4.2). Once the offset has been set it will be retained in the FT702LT Flash memory.
2.5 Error Detection
The FT702LT 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 6.4.25 & 6.4.26). 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.
2.6 Heater Setup
The FT702LT 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 using a user
programmable ‘set point’ temperature. The FT702LT 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 recommended heater set point temperature for most applications is 30°C, however by default the heater is
disabled. To enable the heater or change the heater set point temperature, use the FT702LT Acu-Vis software
(see section 4.2).
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 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 of the sensor, please refer to section 6.4.12.
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.
In low temperature environments where a wind sensor may have accumulated ice prior to power being applied,
it is recommended that a User Reset Command (see section 6.4.16) is sent after the sensor has been powered
for a de-icing period of 30mins. This is to ensure that the sensor initialises correctly with the sensing area clear.

Section 3 Installation
12 FT702LT 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 via a 5-way multipole connector located in the base of the
wind sensor housing. The connector pin designations are shown in Figure 4 and the connector/mating
connector manufacturer’s part numbers in Figure 5.
Figure 4: Sensor Connector Pin
Connector Type
Connector
Description
Manufacturers Part Number
FT Sensor
Type
Maximum Outer
Cable Diameter
Manufacturer
FT702LT Cable
Side Connector
5 way plug
SE104Z053-130/8.7
FT702LT
RS-485 Option
8.0mm
W.W.Fischer
FT702LT Cable
Side Connector
5 way plug
SX2F1C-P05NJH9-0001
FT702LT
RS-485 Option
9.2mm
ODU
Figure 5: Connector Sourcing Options
3.1.2 Cable Details
The mating connectors for the FT702LT 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
13 FT702LT Flat Front Wind Sensor Manual
3.1.3 RS-485 Protocol
The FT702LT is fitted with an RS485 half-duplex serial interface. Slew-rate limited drivers are used to reduce
EMI, and minimize reflections from improperly terminated transmission lines and stubs. The signal state
definitions for the serial interface data lines are as follows:
- The idle, marking, logical “1”, OFF or stop bit state is defined by a negative voltage on line A with
respect to line B.
- The active, spacing, logical “0”, ON or start bit state is defined by a positive voltage on line A with
respect to line B.
Figure 6 shows the recommended wiring diagram for connecting the FT702LT to the computer.
If two or more wind sensors are to be installed it is possible to use the same 2-wire data link to connect all the
FT702LT units to the computer.
Before using an FT702LT in a multi-device system, the Listener identifier of each FT702LT must be set to a
unique value. Use the ID command (Section 6.4.13) to set the Listener identifier for each FT702LT. If the
Listener identifiers are being set in the final host system, then it is important that only one FT702LT be
connected at a time to the RS485 bus until all devices have been assigned a unique Listener ID.
Great care should be exercised when using the ‘//’ characters for addressing. The ‘//’ address characters can be
used to send a SET command simultaneously to all FT702LT units (for example, to enable or disable filtering).
Under no circumstances should the ‘//’ characters be used with any QUERY commands since this will cause all
FT702LT units to transmit data resulting in bus contention.
Figure 6: RS-485 Connection Diagram for 2 Wind Sensors

Section 3 Installation
14 FT702LT Flat Front Wind Sensor Manual
3.2 Description of Parts
The FT702LT 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 7) 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 7).
Figure 7: 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 offers 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 8).

Section 3 Installation
15 FT702LT Flat Front Wind Sensor Manual
Figure 8: FT702LT-FF with protective sleeve
3.2.1 Alignment
The FT702LT 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 9.
Figure 9: Correct Sensor Alignment

Section 3 Installation
16 FT702LT 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 10: Direct lightning strike
Figure 11: 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
17 FT702LT Flat Front Wind Sensor Manual
Figure 12 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 12: 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
18 FT702LT 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 computer 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 the 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 13 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 13: Protection of equipment against indirect effects

Section 3 Installation
19 FT702LT Flat Front Wind Sensor Manual
3.3.3 Surge protection
All connections from the wind sensor to any computer 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.
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 14
shows how the SPDs should be installed.
Figure 14: FT702LT digital interface surge protection
The supply pair [24VDC / 0VDC] is electrically isolated from the other lines and the chassis. The triple RS-485
signal wires [Data ground, Data A, Data B] are isolated from the other lines and the chassis. The data ground
can be directly connected to the chassis of the data acquisition cabinet.
Some examples of SPDs suitable for this protection are given in Figure 15 below from manufactures, DEHN &
Söhne GmbH. (www.dehn.de) and Phoenix Contact (www.phoenixcontact.com).
Manufacturer
Type
Manufacturers part number
PSU lines
Phoenix Contact
Module (x1)
PT 2PE/S 24 AC
RS485 lines
Dehn
Module (x1) - BCT MOD BE 5 & BCT BAS
919 620 & 919 506
Phoenix Contact
Module (x1)
PT 3-HF-12 DC
Figure 15: Typical SPD configuration used to protect sensor
Figure 16 shows an example of how the wires are up the SPD’s inside a Phoenix Contact control cabinet. The
termination of the cable shield at the wall of the control cabinet using a cable gland is not shown.

Section 3 Installation
20 FT702LT Flat Front Wind Sensor Manual
Figure 16: Example of wiring inside a Phoenix Contact control cabinet