User Guide M211095en-h



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Order Code
Description
Purpose
WMT70Conn
Cable connector
Cable
227567SP
Cable 2 m, cable connector, open leads on one end
Used for analog output or serial communication with two serial ports.
227568SP
Cable 10 m, cable connector, open leads on one end
Used for analog output or serial communication with two serial ports.
237890SP
Cable 15 m, cable connector, open leads on one end
Used for analog output or serial communication with two serial ports.
237889SP
Cable 26 m, cable connector, open leads on one end
Used for analog output or serial communication with two serial ports.
228259SP
RS-485 cable 2 m, cable connector,
open leads on one end
Used for serial communication with RS-485
interface.
228260SP
RS-485 Cable 10 m, cable connector,
open leads on one end
Used for serial communication with RS-485
interface.
227565SP
MAWS cable 10 m
Used for connecting WMT700 to Vaisala Automatic
Weather Station MAWS.
229807SP
AWS520 cable 10 m, shield connected to PE pin
Used for connecting WMT700 to Vaisala Fixed Site
Observation System AWS520.
227566SP
AWS520 cable 10 m, shield not connected to PE pin
Used for connecting WMT700 to Vaisala Fixed Site
Observation System AWS520.
231425SP
ROSA analog cable 10 m, cable connector, open leads on one end
Used for connecting WMT700 to Vaisala Road
Weather System ROSA.
227569SP
Adapter cable for WS425 serial
Used for connecting the WS425 cable to WMT700.
Only applicable for retrofit installations.
227570SP
Adapter cable for WS425 analog frequency output
Used for connecting the WS425 cable to WMT700.
Only applicable for retrofit installations.
227571SP
Adapter cable for WS425 analog voltage output
Used for connecting the WS425 cable to WMT700.
Only applicable for retrofit installations.
ASM210719SP Junction Box with Cable 2 meters
Used when a cable longer than 10 meters is needed.
Junction Box contains terminal blocks that extend the meter cable to a needed length.
WMT700 User Guide
M211095EN-H
28


2.4.4 Cable Tightening Tool
Figure 11 Cable Tightening Tool
WMT700 is shipped with a cable tightening tool (SP. When you insert a cable in the cable tightening tool, it is easier to grip and rotate. After tightening, you can leave the cable tightening tool in place.
Chapter 2 – Product Overview
29


WMT700 User Guide
M211095EN-H
30


3. Functional Description Operating Principle
WMT700 uses the Vaisala WINDCAP ultrasonic sensor technology in wind measurement.
The sensor has an onboard microcontroller that captures and processes data and communicates over serial interfaces.
The wind sensor has an array of three equally spaced ultrasonic transducers on a horizontal plane. Wind speed (WS) and wind direction (WD) are determined by measuring the time it takes the ultrasound to travel from each transducer to the other two.
The wind sensor measures the transit time (in both directions) along the three paths established by the array of transducers. The transit time depends on wind speed along the ultrasonic path. For zero wind speed, both the forward and reverse transit times are the same. With wind along the sound path, the upwind direction transit time increases and the downwind transit time decreases.
The following figure shows how the time shift of the ultrasonic signals is measured and how tailwind and forward wind affect the measurement.
Chapter 3 – Functional Description
31

Figure 12 Ultrasonic Measurement Principle
1
Ultrasonic measurement with zero wind
2
Impact of tailwind on ultrasonic measurement
3
Impact of headwind on ultrasonic measurement
The microcontroller calculates WS from the measured transit times using the following formula:
WMT700 User Guide
M211095EN-H
32


V
W
=0.5·L·(1/t ft r
)
V
W
Wind velocity
L
Distance between two transducers t
f
Transit time in the forward direction t
r
Transit time in the reverse direction
Measuring the six transit times allows
V
w to be computed for each of the three ultrasonic paths. Using
V
w values of two array paths is enough to compute WS and WD.
The different paths of WMT700 and the vectors provided by the wind sensor:
Figure 13 Measurement Paths of WMT700 Measurement paths 1 to 6 of WMT700
L
a
, Lb, L
c
Distance between two transducers
The vectors are calculated as follows:
V
a
=0.5·L
a
·(1/A
1
-1/A
2
)
V
b
=0.5·L
b
·(1/A
3
-1/A
4
)
V
c
=0.5·L
c
·(1/A
5
-1/A
6
)
Chapter 3 – Functional Description
33

The equation depends on the accurate distance of the measurement path (L. The computed wind speeds are independent of altitude, temperature, and humidity, which are canceled out when the transit times are measured in both directions, although the individual transit times depend on these parameters Coordinate Systems Vector and Polar
Calculations
The triangular geometry of the sensor is converted to orthogonal coordinates to achieve the x and y components. Then the sensor converts the wind vectors into polar coordinates.
The measurement results are reported as follows:
• WMT700 reports WS (x, y) as two scalar speeds, one parallel to the NS direction (x)
and the other (y) parallel to the WE direction.
x = -WS × cos (WD)
y = -WS × sin (WD)
• WMT700 reports polar wind speed as a scalar speed in selected units (ms, kt, mph,
km/h).
Polar wind direction is expressed in degrees (°). WMT700 indicates the direction that the wind comes from. North is represented as 0°, East as 90°, South as 180°, and West as 270°.
WMT700 User Guide
M211095EN-H
34

Figure 14 Wind Speed and Direction Presentations (Direction Offset Is 0)


Document code
Testsetup according to
More information
Optiontemperature range
Optionheating
Optionhardware interface
Optionunit used
Optionoutput configuration
Selectionoutput configuration
Optionadapter type
Optionaccessories
Aout1 selected option
Output signal
Swnddiroffset,(angle)
Parameterdefinition
Power supplywire colors
Used heating option
Heating option
Wire type/cable length
Descriptionspare part item
Wmt700connector pin
Open commandto activate the command, press enter
Commanddescription
Wind_getfetches wind calibration information.more information
S command. power must be on for at least 5 seconds after the s
Startcommand.more information
Itemdescription
Bitdescription
G command to fetch the current wmt700 parameters. disable error messages with the command s messages,0
Errors. if all values are valid, wmt700 sends the following response:0,0,0,0you can also use the g
Data message number
Ws425 and sdi messages
Parametername
Parameterdefault
Start command.to stop measurement, use the stop
Wb,wfirmware
Wf output:wff6785672109876.5432.1k99xx5.21.2 ws425 f/g asos data messagewmt700 responds to the wa
Bytedescription
Parameterdefault value
Id character
Wx command with a character fixed-length data message.character
Start command. to stop measurement, use thestop
Problemprobable cause
Error/eventcode
Parameter name
Propertydescription/value
Analog outputs for wind direction
Itemorder code
Configuration mode / measurement
Settingparameter
Start command. you can stop the measurement with the stop
Example of the command and response:
Baud........................................................................ 105clearerr
S............................................................................... 103sleep
Gget message. get parameter.........................................................104h
Jjunction box...............................................................28l



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