Section 2
Functional Description
9
FT702LT/D Flat Front Wind Sensor Manual
2 FUNCTIONAL DESCRIPTION
2.1 Technical Performance
Sensor Performance
1
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 ±10
⁰
of 0
⁰
datum)
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 Port
2
RS485 half duplex, non-isolated relative to power ground
Power Requirements
4
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 99W
3
.
*Only 4A (max) power consumption possible for sensors prior to build
version 22
3
.
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)
