Vaisala WS425 Ultrasonic Wind Sensor User's Guide

Below you will find brief information for Ultrasonic Wind Sensor WS425. This device uses an array of three equally spaced ultrasonic transducers to measure the time it takes sound to travel between them. This information is then used to determine wind speed and direction.
PDF Download
Document
Ultrasonic Wind Sensors
WS425
USER'S GUIDE
M210361en-B
May 2004
PUBLISHED BY
Vaisala Oyj
P.O. Box 26
FIN-00421 Helsinki
Finland
Phone (int.):+358 9 8949 1
Fax:
+358 9 8949 2227
Visit our Internet pages at http://www.vaisala.com/
&copy; Vaisala 2004
No part of this manual may be reproduced in any form or by any
means, electronic or mechanical (including photocopying), nor may its
contents be communicated to a third party without prior written
permission of the copyright holder.
The contents are subject to change without prior notice.
Please observe that this manual does not create any legally binding
obligations for Vaisala towards the customer or end user. All legally
binding commitments and agreements are included exclusively in the
applicable supply contract or Conditions of Sale.
___________________________________________________________________
Table of Contents
CHAPTER 1
GENERAL INFORMATION....................................................... 7
About This Manual ................................................. 7
Contents of This Manual ...................................... 7
Version Information .............................................. 8
Feedback.............................................................. 8
Safety..................................................................... 11
General Safety Considerations........................... 11
Product Related Safety Precautions................... 11
Absolute Maximum Voltages.......................... 11
ESD Protection................................................... 12
Regulatory Compliances...................................... 13
EN55011 Class A Group 1 &amp; EN50082-2........... 13
MIL-STD-426 Method RS03 ............................... 13
MIL-STD 810 Method 501 Process 1 ................. 13
MIL-STD 202 Method 213 .................................. 14
Third-Party Testing (Field Tests Included).......... 14
NWS ASOS Mechanical Wind Sensor
Replacement .................................................. 14
Lawrence Livermore Labs.............................. 14
Tennessee Valley Authority............................ 14
CETIAT (Centre Technique des Industries
A&eacute;raulique et Thermiques) ............................. 15
Trademarks ........................................................... 15
License Agreement .............................................. 15
Warranty ................................................................ 15
CHAPTER 2
PRODUCT OVERVIEW .......................................................... 17
Introduction to WS425 ......................................... 17
Measuring Principle............................................ 17
Sensor Operating Modes ................................... 18
Sensor Features ................................................... 19
Polar Wind Speed and Direction ........................ 20
Wind Speed X and Y Components..................... 20
Scalar Averaging of Wind Speed and Direction.. 21
Vector Averaging of Wind Speed and Direction . 22
VAISALA __________________________________________________________1
User's Guide ________________________________________________________
Wind Direction Coasting .................................... 22
Gust Wind Speed and Direction Over Time ....... 23
CHAPTER 3
INSTALLATION...................................................................... 25
Selecting Location ............................................... 25
Installation Procedure ......................................... 25
Unpacking Instructions....................................... 25
Factory Settings................................................. 26
RS-232 Default Settings for USA................... 26
Default Settings of RS-232, RS-422, and RS485 for Europe............................................... 27
Mounting ............................................................ 30
Mounting Procedure on a 1-inch IPS Vertical
Pipe ............................................................... 30
Alignment........................................................... 30
Magnetic Declination Correction.................... 30
Compass Alignment with a Mast Adapter ...... 32
Connections ......................................................... 35
Powering............................................................... 37
Power Supplies.................................................. 37
CHAPTER 4
OPERATION........................................................................... 39
Analog Mode......................................................... 39
Wind Speed ....................................................... 39
Wind Direction ................................................... 41
Missing Readings............................................... 42
Serial Mode........................................................... 42
Overview............................................................ 42
Serial Mode Default Settings for the USA...... 43
Serial Mode Default Settings for Europe........ 44
Configuration Menu ........................................... 44
Configuration Commands .................................. 45
Handar RS232............................................... 46
Identify Command I ....................................... 46
Measurement Command Wx ......................... 46
Missing Readings ...................................... 47
Measurement Unit Change Command Ux ..... 48
NMEA Standard............................................. 48
Missing Readings ...................................... 49
NMEA Extended Message............................. 49
WAT11 Message ........................................... 51
Missing Readings ...................................... 52
2 ______________________________________________________ M210361en-B
___________________________________________________________________
Wind Speed Units............................................... 52
Average Interval ................................................. 53
Averaging Method .......................................... 53
Scalar Averaging........................................ 53
Vector Averaging ....................................... 54
Output Interval.................................................... 54
Sensor ID Character........................................... 55
Wind Direction Coast Threshold......................... 55
Head Orientation ................................................ 56
Bit Rate .............................................................. 56
Parity .................................................................. 56
Data Bits............................................................. 57
Save Configuration............................................. 57
Zero Speed Calibration ...................................... 57
Resume Operation ............................................. 58
SDI-12 Protocol..................................................... 58
SDI-12 Support Group........................................ 58
SDI-12 Electrical Interface.................................. 59
Serial Data Line.................................................. 59
Voltage Transitions............................................. 59
Impedance.......................................................... 60
SDI-12 Communications Protocol ...................... 60
Baud Rate and Byte Frame Format.................... 61
Two Different Submodes.................................... 61
Standard SDI-12 Commands Supported by
WS425 ............................................................... 63
Acknowledge Active Command (a!) ............... 63
Send Identification Command (aI!)................. 64
Address Query Command (?!) ....................... 65
Change Address Command (aAb!) ................ 65
Start Measurement Command (aM!).............. 66
Send Data Command (aD0!).......................... 67
Continuous Measurements (aR0!) ................. 69
Start Verification (aV!) .................................... 71
Vaisala-specific SDI-12 Commands Supported
by WS425........................................................... 72
Measurement Unit Change (aXUx!) ............... 72
Heater Control Command (aXHx!) ................. 73
Check Current Submode (aX?!) ..................... 74
Place Sensor in Submode B (aXQx;c.c;n;yyyy!)74
Reset the Sensor to Submode A Command
(aXS!) ............................................................. 75
Check Current Measurement Unit (aX*!)........ 76
SDI-12 TIMING................................................... 77
VAISALA __________________________________________________________3
User's Guide ________________________________________________________
CHAPTER 5
MAINTENANCE ..................................................................... 81
Periodic Testing ................................................... 81
CHAPTER 6
TROUBLESHOOTING ........................................................... 83
Common Problems .............................................. 83
Frequently Asked Questions (FAQ) ................... 83
Instructions for Opening a Serial Terminal
Connection to WS425 ........................................ 85
Technical Support................................................ 86
Return Instructions .............................................. 86
CHAPTER 7
TECHNICAL DATA ................................................................ 89
Specifications....................................................... 89
APPENDIX A
List of Figures
Figure 1
Figure 2
Figure 3
Figure 4
Figure 5
Figure 6
Figure 7
Figure 8
Figure 9
Figure 10
Figure 11
Figure 12
Figure 13
Figure 14
Figure 15
Figure 16
Different Wind Speed and Direction Presentations 20
Mounting the Sensor to Adapter ............................ 28
WS425 Main Dimensions....................................... 29
Sketch of Magnetic Declination.............................. 31
Suunto Compass MC-2.......................................... 32
Correctly Aligned WS425 Ultrasonic Wind Sensor. 33
Adjusting the N-S Heads........................................ 34
Open-Lead Cables for WS425 Sensors ................. 36
Frequency Connection ........................................... 40
Wind Speed ........................................................... 41
Analog Connection................................................. 42
Timing Diagram...................................................... 78
Verifier.................................................................... 82
WS425FIX30 Adapter ............................................ 91
WS425FIX60 Adapter ............................................ 92
WS425FIX60 Adapter ............................................ 93
4 ______________________________________________________ M210361en-B
___________________________________________________________________
List of Tables
Table 1
Table 2
Table 3
Table 4
Table 5
Table 6
Table 7
Table 8
Table 9
Table 10
Table 11
Table 12
Table 13
Table 14
Table 15
Table 16
Manual Revisions ..................................................... 8
Sensor Ordering Options vs. Supported Data
Outputs ..................................................................... 9
Ordering Codes ...................................................... 10
Maximum Voltages ................................................. 12
Sensor Features ..................................................... 19
Wind Direction Coasting ......................................... 22
Gust Wind Speed and Direction Over Averaging
Time ....................................................................... 23
WS425 Sensor Pins ............................................... 35
The Handar RS232 Polling Commands.................. 46
The RS-232 19-character Fixed Length Output
Message ................................................................. 47
Checksum Table..................................................... 51
Consecutive Measurements of Wind Direction ....... 55
Logic and Voltage Level for Serial Data ................. 59
Byte Frame Format for SDI-12 ............................... 61
SDI Timing Chart .................................................... 62
Technical Specifications ......................................... 89
VAISALA __________________________________________________________5
User's Guide ________________________________________________________
This page intentionally left blank.
6 ______________________________________________________ M210361en-B
Chapter 1 ___________________________________________ General Information
CHAPTER 1
GENERAL INFORMATION
This chapter provides general notes for the product.
About This Manual
This manual provides information for installing, operating,
and maintaining the WS425 Ultrasonic Wind Sensors.
Contents of This Manual
This manual consists of the following chapters:
- Chapter 1, General Information, provides general notes
for the product.
- Chapter 2, Product Overview, describes the features of
the WS425 Ultrasonic Wind Sensors.
- Chapter 3, Installation, provides you with information
that is intended to help you install this product.
- Chapter 4, Operation, explains the operation and
programming of WS425.
- Chapter 5, Maintenance, provides you with general
maintenance information.
- Chapter 6, Troubleshooting, provides you information on
common problems
VAISALA __________________________________________________________7
User's Guide ________________________________________________________
- Chapter 7, Technical Data, gives the technical data on the
product.
- Appendix A includes detailed pictures of the adapters.
Version Information
Table 1
Manual
Code
U428en-1.1
Manual Revisions
Description
Applicable to Models WAS425A and
WAS425AH Firmware versions 1.04.
M210361en- Previous version of the manual.
A
M210361en- This manual. Corrections to Table 8, Figure 11,
B
and to the measurement range of the wind
speed in the technical data.
Feedback
Vaisala Documentation Team welcomes your comments
and suggestions on the quality and usefulness of this
publication. If you find errors or have other suggestions for
improvement, please indicate the chapter, section, and page
number. You can send comments to us by e-mail:
[email protected]
8 ______________________________________________________ M210361en-B
Chapter 1 ___________________________________________ General Information
Table 2
Sensor Ordering Options vs. Supported Data
Outputs
Sensor Ordering
Sensor Cable
Options
WS425 x 1 ... (Analog/ SDI-12 cable
SDI-12/RS-232USA)
Analog cable
WS425 x 2 ... (RS232/
RS-485/RS-422
Supported
Operating Modes
SDI-12 submode A
SDI-12 submode B
Analog mode
RS-232 cable
Serial mode with
wind speed unit =
miles per hour
RS-232 cable
Serial mode with
wind speed unit =
meters per second
RS-422/
RS-485 cable
Supported Data
Outputs
SDI-12 standard
commands
WS [Hz] 0 ... 65
WS [V] 0 ... 1
WD [V] 0 ... Vref
RS-232
NMEA message
Vaisala WATT 11
message
Vaisala Handar
message
RS-232
NMEA message
Vaisala WATT 11
message
Vaisala Handar
message
RS-422
NMEA message
Vaisala WATT 11
message
Vaisala Handar
message
RS-485
NMEA message
Vaisala WATT 11
message
Vaisala Handar
message
VAISALA __________________________________________________________9
User's Guide ________________________________________________________
Table 3
Ordering Codes
Old code
425A
425AH
425S
425SH
WAS425A and WAS425AC
WAS425AH and
WAS425AH-C
WAS425S and WAS425SC
WAS425SH and
WAS425SH-C
425T
425T-1
425L
425SAMS
425AHW-1
425NWS
New code
WS425
WS425
WS425
WS425
WS425
A
B
A
B
A
1
1
1
1
2
A
A
A
A
A
1
1
1
1
2
B
B
B
B
B
WS425
B
2
A
2
B
WS425
A
2
A
2
B
WS425
B
2
A
2
B
WS425
WS425
WS425
WS425
WS425
WS425
B
B
A
C
E
D
3
4
5
1
6
7
A
A
A
A
A
A
4
4
1
1
1
1
A
A
A
A
A
A
10 _____________________________________________________ M210361en-B
Chapter 1 ___________________________________________ General Information
Safety
General Safety Considerations
Throughout the manual, important safety considerations are
highlighted as follows:
WARNING
Warning alerts you to a serious hazard. If you do not read
and follow instructions very carefully at this point, there is
a risk of injury or even death.
CAUTION
Caution warns you of a potential hazard. If you do not read
and follow instructions carefully at this point, the product
could be damaged or important data could be lost.
NOTE
Note highlights important information on using the product.
Product Related Safety
Precautions
Absolute Maximum Voltages
The absolute maximum voltages that may be applied to
WS425 sensor are listed in Table 4 on page 12. The
following limits do not damage the sensor but they are not
operational limits.
VAISALA _________________________________________________________11
User's Guide ________________________________________________________
Table 4
Maximum Voltages
Pin Min. volts Max. volts
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
-0.3
-0.3
5.3
5.3
-12.0
-12.0
-0.5
-0.5
-10.0
-10.0
-0.5
-5.0
20.0
20.0
18.0
5.3
12.0
12.0
5.3
42.0
Ordering Options
WS425 x 2 ... WS425 x 1 ...
Ground
Ground
Ground
Ground
Ground
Ground
N/C
N/C
Jumper
Jumper
Jumper
Jumper
Ground
Ground
Ground
Ground
Digital Output Digital Output
Digital Input
Digital Input
+12 V Power
+12 V Power
Digital Output Analog Input
N/C
Analog Output
Digital Input
Analog Output
N/C
Analog Output
Heater Power Heater Power
ESD Protection
Electrostatic Discharge (ESD) can cause immediate or latent
damage to electronic circuits. Vaisala products are
adequately protected against ESD for their intended use.
However, it is possible to damage the product by delivering
electrostatic discharges when touching, removing, or
inserting any objects inside the equipment housing.
To make sure you are not delivering high static voltages
yourself:
- Handle ESD sensitive components on a properly
grounded and protected ESD workbench. When this is
not possible, ground yourself to the equipment chassis
before touching the boards. Ground yourself with a wrist
strap and a resistive connection cord. When neither of the
above is possible, touch a conductive part of the
equipment chassis with your other hand before touching
the boards.
12 _____________________________________________________ M210361en-B
Chapter 1 ___________________________________________ General Information
- Always hold the boards by the edges and avoid touching
the component contacts.
Regulatory Compliances
The Vaisala WS425 Ultrasonic Wind Sensor has been tested
to fulfill the following regulatory compliances. Also
mentioned here are some third-party tests that involved field
testing of the sensor.
EN55011 Class A Group 1 &amp;
EN50082-2
- Radiated emissions
- Conducted emission
- Electrostatic discharge
- Radiated susceptibility
- Conducted susceptibility
- Electrical task transient burst surge
- Magnetic susceptibility
- Voltage dips &amp; interrupts
MIL-STD-426 Method RS03
- Electromagnetic compatibility
MIL-STD 810 Method 501
Process 1
- Salt spray test
VAISALA _________________________________________________________13
User's Guide ________________________________________________________
MIL-STD 202 Method 213
- Mechanical shock
Third-Party Testing (Field Tests
Included)
NWS ASOS Mechanical Wind Sensor
Replacement
Vaisala has participated in a three-year test program
conducted by the U.S. National Weather Service ASOS
Program group. The NWS has conducted a variety of tests
including wind tunnel tests from 0 to 120 knots and field
tests in various locations.
Lawrence Livermore Labs
Lawrence Livermore Labs tested the sensor independently
and Grank Gouveia and Ron Baskett have published a paper
titled Evaluation of a New Sonic Anemometer for Routing
Monitoring and Emergency Response Applications. A
second paper titled Comparison of In-Situ Data from the
Handar Sonic Anemometer and the Met One Cup and Vane
[AMS proceedings of the 10th symposium on
Meteorological Observations and Instrumentation]
published by Frank Gouveia and Thomas Lockhart.
Tennessee Valley Authority
The TVA conducted comparative field tests of mechanical
cup and vane sensors versus the Vaisala WS425 Ultrasonic
Wind Sensor. The results were published in the AMS
conference in 2001 by authors Kenneth G. Wastrack and
Doyle E. Pittman et al.
14 _____________________________________________________ M210361en-B
Chapter 1 ___________________________________________ General Information
CETIAT (Centre Technique des Industries
A&eacute;raulique et Thermiques)
CETIAT has evaluated the accuracy of the WS425
Ultrasonic Wind Sensor in a wind tunnel against a laser
Doppler anemometer (LDA) reference sensor.
Trademarks
Microsoft, Windows, and Windows NT are registered
trademarks of Microsoft Corporation in U.S. and/or other
countries.
License Agreement
All rights to any software are held by Vaisala or third
parties. The customer is allowed to use the software only to
the extent that is provided by the applicable supply contract
or Software License Agreement.
Warranty
For certain products Vaisala normally gives a limited oneyear warranty. Please observe that any such warranty may
not be valid in case of damage due to normal wear and tear,
exceptional operating conditions, negligent handling or
installation, or unauthorized modifications. Please see the
applicable supply contract or conditions of sale for details of
the warranty for each product.
VAISALA _________________________________________________________15
User's Guide ________________________________________________________
This page intentionally left blank.
16 _____________________________________________________ M210361en-B
Chapter 2 _____________________________________________Product Overview
CHAPTER 2
PRODUCT OVERVIEW
This chapter describes the features of the WS425 Ultrasonic
Wind Sensors.
Introduction to WS425
Measuring Principle
The WS425 Ultrasonic Wind Sensor has an on-board
microcontroller that captures and processes data and
performs serial communications.
The wind sensor has an array of three equally spaced
ultrasonic transducers on a horizontal plane. The sensor
measures transit time, the time that it takes the ultrasound to
travel from one transducer to another. The transit time is
measured in both directions.
The transit time depends on the wind velocity along the
ultrasonic path. For zero wind velocity, both the forward
and reverse transit times are the same. With wind along the
sound path, the up-wind transit time increases and the
down-wind transit time decreases.
The microprocessor of the microcontroller calculates the
wind speed from the transit times using the following
formula:
VAISALA _________________________________________________________17
User's Guide ________________________________________________________
VW = 0.5 ⋅ L ⋅ (1/t f − 1 / t r )
where:
Vw
=
Wind velocity
L
=
The distance between two transducers
tf
=
The transit time in the forward direction
tr
=
The transit time in the reverse direction.
Measuring the six transmit times allows wind velocity to be
calculated for each of the three ultrasonic paths, which are
offset to each other by 120&deg;. The calculated wind speeds are
independent of altitude, temperature, and humidity because
they cancel out with the six measurements even though the
velocity of sound affects individual transit times.
Incorrect readings may occur when a large raindrop or ice
pellet hits a transducer. They are eliminated by a proprietary
signal processing technique. The wind velocity that is most
affected by turbulence error is eliminated so that wind speed
and wind direction are calculated from the best two vectors.
Sensor Operating Modes
There are four modes of operation that give different
information:
- Analog
- SDI-12 mode A
- SDI-12 mode B
- Serial mode RS-232/422/485
Only one of these modes can be operated at a time. The
sensor must be ordered according to the desired mode of
operation.
18 _____________________________________________________ M210361en-B
Chapter 2 _____________________________________________Product Overview
Sensor Features
Some of the sensor features depend on the WS425 operating
mode. Table 5 below outlines where the features are
available.
Table 5
Sensor Feature
Polar wind speed and
direction
Wind speed x and y
components
Scalar averaging of
wind speed and
direction
Vector averaging of
wind speed and
direction
Wind direction
coasting
Wind direction
reversible for upside
down mounting
Enable/disable heater
command
Selectable wind speed
unit
Gust wind speed and
direction over
averaging time
Low-current standby
(sensor sleep)
Current with 1 Hz
measurement
Data acquisition by
polling
Continuous data
transmission
Sensor Features
Operating Mode
Serial
Analog
Yes
Yes
SDI-12
submode A
Yes
SDI-12
submode B
Yes
No
No
Yes
Yes
1 s ... 9 s
No
No
3 s ... 1 h
1 s ... 9 s
No
No
3 s ... 1 h
Yes
No
No
Yes
Yes
No
No
No
No
No
Yes
Yes
Yes
No
Yes
Yes
Calculate
from instant
data
No
Calculate
from instant
data
No
Yes
Yes
18 mA@
12 VDC
Yes
12 mA@
12 VDC
No
0.2 mA@
12 VDC
7.7 mA@
12 VDC
Yes
7.7 mA@
12 VDC
12 mA@
12 VDC
Yes
1 ... 9 s
interval
Yes
No
No
VAISALA _________________________________________________________19
User's Guide ________________________________________________________
Polar Wind Speed and Direction
The wind speed (WS) is represented as a scalar speed in
selected units (m/s, kt, mph, km/h). The wind direction
(WD) is expressed in degrees (&deg;).
0212-044
Figure 1
Different Wind Speed and Direction
Presentations
Wind Speed X and Y
Components
The wind speed (x, y) is represented as two scalar speeds,
one parallel to the N-S direction (x) and the other (y)
parallel to the W-E direction The speed unit may be m/s, kt,
mph, or km/h.
x = WS &times; cos (WD)
y = WS &times; sin (WD)
20 _____________________________________________________ M210361en-B
Chapter 2 _____________________________________________Product Overview
Scalar Averaging of Wind Speed
and Direction
The scalar average of wind speed and wind direction is
available in both SDI-12 submode B and serial modes. The
time between each consecutive wind speed and wind
direction measurement is one second. Each wind speed
measurement taken over the preceding averaging interval is
summed and the sum is then divided by the number of
measurements.
The sensor computes the true running average. If the Data
Acquisition System requests data before the initial
averaging interval completes, the sensor returns the best
possible running average.
In SDI-12 submode B, the average is determined over the
averaging interval specified, which ranges from three
seconds to one hour.
In RS-232 mode, the average is determined over the
averaging interval specified, which ranges from one to nine
seconds.
Wind direction is a circular function with a discontinuity at
north, where 360 degrees is equal to zero degrees. For
example:
359&deg; + 5&deg; = + 4&deg;
0&deg; - 5&deg; = 355&deg;
The microprocessor translates the circular function to a
linear function so that 359&deg; + 5&deg; is translated to 364&deg;. Also,
0&deg; - 5&deg; translated to 355&deg;. This way the wind direction
average stays representative of the true situation even if
individual samples occur in both sides of the zero direction.
VAISALA _________________________________________________________21
User's Guide ________________________________________________________
Vector Averaging of Wind
Speed and Direction
The vector average is available in SDI-12 submode B and
serial mode. Each x velocity and y velocity measurement
over the averaging interval is added and then divided by the
number of measurements. The resultant average x velocity
and average y velocity are converted to polar direction and
magnitude, returning as the average direction in degrees and
speed in the chosen units. The average is determined over
the specified averaging interval (0 ... 9 s for serial mode,
3 s ... 1 h for SDI-12 submode B). The sensor computes a
true running average. If the DAS requests data before the
initial averaging interval completes, the sensor returns the
best possible running average. The averaging calculation
uses the direction coast speed.
Wind Direction Coasting
At very low wind speeds, the measured wind direction is
meaningless. Therefore, you can specify a direction coast
speed. When the measured wind speed drops below the
direction coast speed, the calculations use the last wind
direction that occurred while the wind speed was at or above
the direction coast speed to the average wind direction. You
can specify a direction coast speed between 0.0 and 9.9
units of measurement. Use 0.0 if coasting is not required.
For example, making the direction coast speed = 2.0. The
consecutive measurements are presented in Table 6 below.
Table 6
Wind Direction Coasting
Measured Wind
Speed
Measured Wind
Direction
3.5
2.5
2.2
1.9
350
340
340
175
Wind Direction
Used for
Averaging
350
340
340
340 (coasting)
22 _____________________________________________________ M210361en-B
Chapter 2 _____________________________________________Product Overview
Measured Wind
Speed
Measured Wind
Direction
1.2
2.1
045
345
Wind Direction
Used for
Averaging
340 (coasting)
345
Gust Wind Speed and Direction
Over Time
The gust wind speed and direction are available in SDI-12
submode B. It is the highest wind speed and direction
recorded during the averaging interval. The gust averaging
count can be specified, which is the number of
measurements (one measurement each second) average to
produce the gust values for speed and direction. It has a
range of one to nine counts. As a gust averaging count is
specified as one, the reported wind gust is the highest
instantaneous reading. An example of a gust averaging
count of five will follow. In this example of 14
measurements shown in Table 7 below, measurement 13
has the highest instantaneous wind gust reading.
Table 7
Measurement
Wind speed
Highest sum of 5
Gust averaging
sum of last 5
Gust wind speed
(sum of highest
5) divided by 5
Sum of all wind
speed
Average wind
speed
Gust Wind Speed and Direction Over
Averaging Time
1
8
-
2
7
-
3
6
-
4
3
-
5
5
29
[29]
6
3
29
[24]
7
4
29
[21]
8
9
29
[24]
9
8
29
[29]
10
7
31
[31]
11
6
34
[34]
12
10
40
[40]
13
12
43
[43]
14
11
46
[46]
-
-
-
-
5.8
5.8
5.8
5.8
5.8
6.2
6.8
8.0
8.6
9.2
8
15
21
24
29
32
36
45
53
60
66
76
88
99
8
7.5
7.0
6.0
5.8
5.3
5.1
5.6
5.9
6.0
6.0
6.3
6.8
7.1
VAISALA _________________________________________________________23
User's Guide ________________________________________________________
This page intentionally left blank.
24 _____________________________________________________ M210361en-B
Chapter 3 __________________________________________________ Installation
CHAPTER 3
INSTALLATION
This chapter provides you with information that is intended
to help you install this product.
Selecting Location
WS425 Ultrasonic Wind Sensor should be installed in a
location that is free from turbulence caused by nearby
objects, such as trees or buildings. Ideally, the sensor should
be higher than any other object within the horizontal radius
of 300 m.
WARNING
To protect personnel (and the wind sensor), a lightning rod
must be installed with the tip at least one meter above the
wind sensor. The rod must be properly grounded,
compliant with all local applicable safety regulations.
Installation Procedure
Unpacking Instructions
The ultrasonic wind sensor comes in a custom shipping
container. The sensor must be removed from the container
VAISALA _________________________________________________________25
User's Guide ________________________________________________________
carefully. It is important to save the container and all the
foam packing for future transporting or shipping.
The sensor comes with a Hex-socket bolt and a grooved bolt
to be used in mounting.
CAUTION
Never move the WS425 Ultrasonic Wind Sensor until it is
in its custom shipping container. Otherwise, the warranty
will become void.
CAUTION
A transducer is located at the top of each of the three arms.
Be careful not to damage any of the transducers. Dropping
the sensor can break or damage the transducer or the arms
will bend and they cannot be re-aligned. Damage can also
be caused if the transducers are twisted (the transducers are
not screwed into the arms).
Factory Settings
There are two different factory settings available for WS425
if a serial RS-232 protocol is used. For RS-485 and RS-422
protocols, only a single factory configuration is available.
RS-232 Default Settings for USA
Vaisala WS425 Ultrasonic Anemometer, Firmware Version
v6.04.
Operation Mode:
Wind Speed Units:
Average Interval (seconds):
Averaging Method:
Output Interval (seconds, 0 for polled):
Sensor ID Character:
Wind Direction Coast Threshold
(speed units):
Head Orientation:
Handar RS232
Miles/Hour
1
Scalar
0
A
0.0
Up
26 _____________________________________________________ M210361en-B
Chapter 3 __________________________________________________ Installation
Baud Rate:
Parity:
Data Bits:
Save Configuration
Do Zero Speed Calibration
Resume Operation
NOTE
2400b
None
8
These default settings are delivered with product ordering
options x1xxx (for example, WS425 A1A2A, where the
number 1 refers to the default settings).
Default Settings of RS-232, RS-422, and
RS-485 for Europe
Operation Mode:
Wind Speed Units:
Average Interval (seconds):
Averaging Method:
Output Interval (seconds, 0 for polled):
Sensor ID Character:
Wind Direction Coast Threshold
(speed units):
Head Orientation:
Baud Rate:
Parity:
Data Bits:
NOTE
NMEA Extended
Meters/Second
3
Scalar
1
A
0.0
Up
9600b
None
8
These default settings are delivered with product ordering
options x2xxx (for example, WS425 A2A1A, where the
number 2 refers to the default settings.)
VAISALA _________________________________________________________27
User's Guide ________________________________________________________
0311-011
Figure 2
Mounting the Sensor to Adapter
The following numbers refer to Figure 2 above.
1=
2=
3=
4=
5=
6=
7=
Sensor body
Cable connector
Spacer ring
3/16 inch Hex-socket bolt or standard screw
Sensor adapter
Fastening clamp
Vertical tube
The dimensions of the adapter are illustrated in Figure 3 on
page 29.
28 _____________________________________________________ M210361en-B
Chapter 3 __________________________________________________ Installation
0212-045
Figure 3
WS425 Main Dimensions
The dimensions are in millimeters.
VAISALA _________________________________________________________29
User's Guide ________________________________________________________
Mounting
Mounting Procedure on a 1-inch IPS Vertical
Pipe
Use the following procedure to mount the sensor to a
vertical 1-inch International Pipe Standards (IPS) pipe.
WS425FIX30 is suitable for the 1-inch IPS vertical pipe and
WS425FIX60 is suitable for a 60-mm vertical pipe
(Europe). See Figure 2 on page 28 for details.
To mount the sensor, do the following:
1.
Remove the hex-socket bolt or standard screw shown
in Figure 2 on page 28 (use 3/16-inch Allen key or a
crosshead screwdriver).
2.
Connect the cable to the sensor, routing it through the
adapter.
3.
Attach the adapter to the sensor body and tighten the
bolt.
4.
Run the cable out of the adapter slot between the
sensor and the clamp. Optionally, you can run the cable
inside the vertical pipe.
5.
Place the sensor on the pipe and slightly tighten the
clamp’s bolt.
6.
Align wind direction as explained in section Alignment
on page 30.
Alignment
Magnetic Declination Correction
One transducer arm is permanently marked with an N for
north and another with an S for south.
30 _____________________________________________________ M210361en-B
Chapter 3 __________________________________________________ Installation
NOTE
Aligning might be easier if you mark the sensor body, for
example, with paint or colored tape, to indicate north and
south so that it can be seen from the ground.
Wind direction can be referenced to either the true north,
which uses the earth’s geographic meridians, or to the
magnetic north, which is read with a magnetic compass. The
magnetic declination is the difference in degrees between
the true north and magnetic north. See Figure 4 below.
0003-011
Figure 4
NOTE
Sketch of Magnetic Declination
The source for the magnetic declination must be current as
the declination changes over time.
VAISALA _________________________________________________________31
User's Guide ________________________________________________________
0212-048
Figure 5
Suunto Compass MC-2
Compass Alignment with a Mast Adapter
The following steps aim the wind sensor when using the
1-inch adapter for mounting.
1.
Use the compass to determine that the N-S transducer
heads of the ultrasonic wind sensor are exactly in line
with the compass. Adjust the heads by moving them to
the left or right. For the correct ground position of the
installer, see Figure 7 on page 34.
2.
If the alignment is not correct, lower the tower.
3.
Loosen the clamp at the bottom of the sensor’s adapter
and rotate the sensor so that the heads marked with the
N and with the S are exactly aligned to north and south
when the tower is set up. Tighten the clamp.
32 _____________________________________________________ M210361en-B
Chapter 3 __________________________________________________ Installation
4.
Raise the tower to the vertical position. Figure 6 below
shows the correct alignment.
0208-025
Figure 6
Correctly Aligned WS425 Ultrasonic Wind
Sensor
VAISALA _________________________________________________________33
User's Guide ________________________________________________________
0208-024
Figure 7
Adjusting the N-S Heads
The following letters refer to Figure 7 above.
A = The installer is too far to the left.
B = The installer is in line with the sensor.
C = The sensor's appearance is shown when the installer is
in the correct position. The sensor, however, is not
correctly aligned.
34 _____________________________________________________ M210361en-B
Chapter 3 __________________________________________________ Installation
Connections
WS425 has a 16-pin circular plastic connector (male) at the
bottom of the sensor. A cable connector of type
AMP206037-1 can be used to attach wires to the sensor
pins.
Table 8 below illustrates usage of the pins with different
protocols.
Table 8
WS425 Sensor Pins
Sensor
Pin No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
NOTE
Protocol
RS-232
GND
GND
GND
RS-422
GND
GND
GND
-
RS-485
GND
GND
GND
-
GND
Data out (T-)
Data in (R-)
+12 VDC
Data out (T+)
Data in (R+)
+36 VDC
GND
RTRT+12 VDC
RT+
RT+
+36 VDC
-
GND
Data out (TxD)
Data in (RxD)
+12 VDC
+36 VDC
Analog
GND
GND
GND
-
SDI-12
GND
GND
GND
GND
GND
GND
SDI data
+12 VDC
+12 VDC
WD Vref in WD Vout
WS Fout
WS Vout
+36 VDC
+36 VDC
The short-circuits between pins 5, 6, and 7 are required for
selecting the protocol.
VAISALA _________________________________________________________35
User's Guide ________________________________________________________
0212-041
Figure 8
Open-Lead Cables for WS425 Sensors
The following 10-meter cables are available from Vaisala.
Choose the cable according to the desired communication
protocol.
36 _____________________________________________________ M210361en-B
Chapter 3 __________________________________________________ Installation
Powering
Power Supplies
You can use any 12 VDC power supply with the unheated
Ultrasonic Wind Sensors, as long as it meets all applicable
safety regulations. Typically, the power supply is a fused
12 V battery with either a solar panel charger or a trickle
charger.
NOTE
Some DC power supplies are based on a chopper circuit
that operates at a 100 kHz frequency. Avoid using such
power supplies with WS425 since the measurement can be
distorted by the ripple in the DC output.
The heated ultrasonic wind sensors require +12 VDC for the
sensor and +36 VDC for the heater.
CAUTION
The heated Ultrasonic Wind Sensor is intended for
operation when pin 16 is connected to a +36 VDC source.
If you are operating WS425 when pin 16 is not connected
to +36 VDC, you must ground pin 16. Never float pin 16
on WS425 because the sensor will not report accurate
readings.
VAISALA _________________________________________________________37
User's Guide ________________________________________________________
This page intentionally left blank.
38 _____________________________________________________ M210361en-B
Chapter 4 ___________________________________________________ Operation
CHAPTER 4
OPERATION
Analog Mode
The WS425 Ultrasonic Wind Sensor can be used as a
conventional wind set that gives instantaneous readings. The
sensor is normally powered down. When power is first
turned on, it takes about two seconds for the sensor to
initialize and stabilize. Then the sensor takes a 0.35-second
measurement and synthesizes the analog outputs of wind
speed and wind direction. The cycle is repeated every
second until power is turned off.
Wind Speed
The factory sets the wind speed unit of the analog mode to
miles per hour. This is the only option available for the
analog mode.
The wind speed output at pin 14 is 0 to 12 V pulsed output
with a frequency proportional to wind speed. Every mile per
hour adds 5 Hz to the frequency. In SI units, a change of
0.894 m/s adds 10 Hz to the frequency. A frequency counter
is required to count the output in Hz and the calculation that
scales the result to appropriate units.
VAISALA _________________________________________________________39
User's Guide ________________________________________________________
0212-039
Figure 9
Frequency Connection
The wind speed output at pin 15 is a voltage that varies
linearly from 0 VDC at 0 mph to 1 VDC at 125 mph. In SI
units, the voltage varies linearly from 0 VDC at 0 m/s to
1 VDC at 55.88 m/s.
40 _____________________________________________________ M210361en-B
Chapter 4 ___________________________________________________ Operation
0212-038
Figure 10 Wind Speed
NOTE
The wind speed voltage output cannot be used
simultaneously with the frequency output. If the voltage
output pin 15 is used, the frequency output pin 14 must be
connected to ground, see Figure 10 above.
Wind Direction
The DC reference voltage that inputs the sensor at pin 12,
produces a voltage that represents the wind position. The
reference voltage must be in the range of 1.0 to 4.0 VDC.
The output at pin 13 is 0 VDC at zero degrees and increases
to the maximum input voltage at 359 degrees.
VAISALA _________________________________________________________41
User's Guide ________________________________________________________
0212-040
Figure 11 Analog Connection
Missing Readings
For analog outputs, the wind speed is set to 125 mph when a
reading is missing.
Serial Mode
Overview
You can use any computer or data logger that has a serial
port to collect the sensor data by using the serial commands.
The communication speed, parity, and number of data bits
for the serial line can be selected by the user. The sensor can
be set to transmit data messages at predefined intervals
(autosending) or it responds to a polling string, which is
specific to a selected output message format. Various
42 _____________________________________________________ M210361en-B
Chapter 4 ___________________________________________________ Operation
operational parameters can be set through a terminal
connection.
NOTE
Since the serial line settings may not be known for a
device, the settings are held as constant for the first five
seconds after powering up the sensor. During this time, the
sensor responds to commands issued with settings such as
9600 bit/s, 8 data bits, parity None, 1 stop bit.
Serial Mode Default Settings for the USA
Vaisala WS425 Ultrasonic Anemometer, Firmware Version
v6.04.
Operation Mode:
Wind Speed Units:
Average Interval (seconds):
Averaging Method:
Output Interval (seconds, 0 for polled):
Sensor ID Character:
Wind Direction Coast Threshold
(speed units):
Head Orientation:
Baud Rate:
Parity:
Data Bits:
Save Configuration
Do Zero Speed Calibration
Resume Operation
NOTE
Handar RS232
Miles/Hour
1
Scalar
0
A
0.0
Up
2400b
None
8
These default settings for the USA are used for product
ordering options x1xxx (for example, WS425 A1A2A,
where number 1 refers to the default settings.)
VAISALA _________________________________________________________43
User's Guide ________________________________________________________
Serial Mode Default Settings for Europe
Operation Mode:
Wind Speed Units:
Average Interval (seconds):
Averaging Method:
Output Interval (seconds, 0 for polled):
Sensor ID Character:
Wind Direction Coast Threshold
(speed units):
Head Orientation:
Baud Rate:
Parity:
Data Bits:
NOTE
NMEA Extended
Meters/Second
3
Scalar
1
A
0.0
Up
9600b
None
8
These default settings for Europe are used for product
ordering options x2xxx (for example, WS425 A2A1A,
where the number 2 refers to the default settings).
Configuration Menu
The configuration menu can be opened by typing
Open
or Open
&lt;id&gt;
where
&lt;id&gt;
is the identification character of the sensor.
If the sensor has been running for more than five seconds,
use the currently active baud rate and other communication
settings. There is a short timeout in typing in the characters.
Therefore, type the OPEN command followed by ENTER
relatively fast.
The OPEN command displays the following menu (on the
next page):
44 _____________________________________________________ M210361en-B
Chapter 4 ___________________________________________________ Operation
Vaisala WS425 Ultrasonic Anemometer
Firmware Version v6.00
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
Operation Mode: WAT11
Wind Speed Units: Meters/Second
Average Interval (seconds): 3
Averaging Method: Vector
Output Interval (seconds, 0 for polled): 0
Sensor ID Character: A
Wind Direction Coast Threshold (speed
units): 1.0
Head Orientation: Up
Baud Rate: 9600b
Parity: None
Data Bits: 8
Save Configuration
Do Zero Speed Calibration
Resume Operation
Enter Function Number:
Each configuration parameter is displayed together with the
currently active setting. The configuration parameters can
be changed by selecting the number of the parameter
followed by ENTER.
NOTE
After modifying the parameters, type 12 for storing the new
parameter values and 14 to exit the configuration menu and
to return to the measurement mode.
Configuration Commands
The first parameter selects the message format and polling
commands for the sensor. The available options are:
a.
Handar RS232
b.
NMEA Standard
c.
NMEA Extended
d.
WAT11
VAISALA _________________________________________________________45
User's Guide ________________________________________________________
Handar RS232
When the sensor uses the Handar RS232 message, it
responds to polling commands used for requesting data from
the sensor. Table 9 below summarizes these commands.
Table 9
The Handar RS232 Polling Commands
Command
I
Wx
Ux
Name
Identify
Measurement
Measurement unit change
Page
46
46
47
Identify Command I
The identify command is I.
The following is an example of the command:
I
VAISALA WS425A/AH 600
Vaisala WS425A/AH is the vendor and model number, 600
is version 6.00 of models WS425A/AH.
Measurement Command Wx
The measurement command is Wx where x is the time for
averaging wind speed and wind direction. x has a range of 1
to 9.
The following is an example of the command:
W5
☻W5P1200013.2TDE♥
The interpretation of the output message is described in
Table 10 on page 47.
46 _____________________________________________________ M210361en-B
Chapter 4 ___________________________________________________ Operation
Table 10
Character
position
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
NOTE
The RS-232 19-character Fixed Length
Output Message
Message
“☻” 02H (&lt;STX&gt;, start of transmission)
“W”
“5” for 5-second running average
“P” for “pass”
“F” for “fail”
Wind direction (most significant digit)
Wind direction (middle digit)
Wind direction (least significant digit)
Wind speed (most significant digit)
Wind speed (next digit)
Wind speed (next digit)
Wind speed (least significant digit)
“.” (dot character)
Wind speed (tenth digit)
“M” for miles per hour; “K” for knots
“L” for kilometers per hour; “T” for meters per
second
Check sum (most significant digit) (See note)
Check sum (least significant digit)
“♥” 03H (&lt;ETX&gt;, end of transmission)
[CR] (carriage return)
[LF] (line feed)
The checksum is calculated from 13 characters from
position 2 through 14. The accumulator initializes at 0 with
the addition of the byte value. The checksum has a range of
0H … FFH.
Missing Readings
If data is missing due to a measurement problem, Handar
RS-232 message reports 999.9 for wind speed.
VAISALA _________________________________________________________47
User's Guide ________________________________________________________
NOTE
The sensor has a 20 ms timeout in receiving characters.
Therefore, polling strings should be transmitted by a
programmable device, not as a user command via terminal
sessions.
Measurement Unit Change Command Ux
The measurement unit change command is Ux.
where
x
x
x
x
=
=
=
=
0, for miles per hour, [mph]
1, for knots (default), [knot]
2, for kilometers per hour, [km/h]
3, for meters per second, [m/s]
The following is an example: U3
It sets meters per second for wind speed.
NMEA Standard
The standard variable length, comma-separated, MWV wind
message is defined by NMEA 0183 V2.20 as follows:
$WIMWV,&lt;dir&gt;,&lt;ref&gt;,&lt;spd&gt;,&lt;uni&gt;,&lt;sta&gt;*&lt;chk&gt;&lt;cr&gt;&lt;lf&gt;
where
$WIMWV
= Fixed text
&lt;dir&gt;
= Wind angle, 0 to 359 degrees
&lt;ref&gt;
= Reference; R=Relative, T=True
&lt;spd&gt;
= Wind speed
&lt;uni&gt;
= Wind speed units; K = kmph [km/h],
M = mps [m/s], N = kt
&lt;sta&gt;
= Status; A = Data Valid, V = Invalid Data
48 _____________________________________________________ M210361en-B
Chapter 4 ___________________________________________________ Operation
NOTE
*
= Fixed text
&lt;chk&gt;
= Checksum
(8-bit XOR, excluding $ and *)
&lt;cr&gt;
= Carriage return code, ASCII 0DH
&lt;lf&gt;
= Line feed code, ASCII 0AH
When the NMEA Standard message format is selected, the
sensor must have a non-zero output interval setting
(parameter 5 in the configuration menu) since no polling
command is defined for this message type.
Missing Readings
If data is missing due to a measurement problem, the
NMEA messages will only show the commas (,) between
the data fields. Thus, NMEA is a variable-length data
message.
NMEA Extended Message
Vaisala extension to the standard MWV wind message is
defined as follows:
$P&lt;id&gt;MWV,&lt;dir&gt;,&lt;ref&gt;,&lt;spd&gt;,&lt;uni&gt;,&lt;sta&gt;*&lt;chk&gt;&lt;cr&gt;&lt;lf&gt;
where
$P
= Fixed text
&lt;id&gt;
= Is the data ID; A … Z
MWV
= Fixed text
&lt;dir&gt;
= Wind angle, 0 to 359 degrees
&lt;ref&gt;
= Reference; R = Relative, T = True
&lt;spd&gt;
= Wind speed
&lt;uni&gt;
= Wind speed units; K = kmph [km/h],
VAISALA _________________________________________________________49
User's Guide ________________________________________________________
M = mps [m/s], N = kt
NOTE
&lt;sta&gt;
= Status; A = Data Valid, V = Invalid Data
*
= Fixed text
&lt;chk&gt;
= Checksum (8-bit XOR, excluding $ and
*)
&lt;cr&gt;
= Carriage return code, ASCII 0DH
&lt;lf&gt;
= Line feed code, ASCII 0AH
The sensor has a 20 ms timeout in receiving characters.
Thus, polling strings should be transmitted by a
programmable device, not as a user command via terminal
sessions.
In NMEA Extended Message, the polling can be done using
the following command:
$WIP&lt;id&gt;Q,*&lt;chk&gt;&lt;cr&gt;&lt;lf&gt;
where
$WIP
= Fixed text
&lt;id&gt;
= Is the data ID; A … Z
Q
= Fixed text
*
= Fixed text
&lt;chk&gt;
= Checksum (8-bit XOR, excluding $ and
*)
&lt;cr&gt;
= Carriage return code, ASCII 0DH
&lt;lf&gt;
= Line feed code, ASCII 0AH
50 _____________________________________________________ M210361en-B
Chapter 4 ___________________________________________________ Operation
Table 11
Checksum Table
ID Character
&lt;id&gt;
A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
NOTE
Checksum
&lt;chk&gt;
72
71
70
77
76
75
74
7B
7A
79
78
7F
7E
7D
7C
Polling String
$WIPA,*72&lt;cr&gt;&lt;lf&gt;
$WIPB,*71&lt;cr&gt;&lt;lf&gt;
$WIPC,*70&lt;cr&gt;&lt;lf&gt;
$WIPD,*77&lt;cr&gt;&lt;lf&gt;
$WIPE,*76&lt;cr&gt;&lt;lf&gt;
$WIPF,*75&lt;cr&gt;&lt;lf&gt;
$WIPG,*74&lt;cr&gt;&lt;lf&gt;
$WIPH,*7B&lt;cr&gt;&lt;lf&gt;
$WIPI,*7A&lt;cr&gt;&lt;lf&gt;
$WIPJ,*79&lt;cr&gt;&lt;lf&gt;
$WIPK,*78&lt;cr&gt;&lt;lf&gt;
$WIPL,*7F&lt;cr&gt;&lt;lf&gt;
$WIPM,*7E&lt;cr&gt;&lt;lf&gt;
$WIPN,*7D&lt;cr&gt;&lt;lf&gt;
$WIPO,*7C&lt;cr&gt;&lt;lf&gt;
When using the sensor in the NMEA Extended mode, you
can either set the output interval to zero (parameter 5 in the
configuration menu) to enable polling or use some fixed
output interval.
WAT11 Message
The fixed length format of the WAT11 message is defined
as follows:
&lt;stx&gt;&lt;id&gt;&lt;spd&gt;&lt;dir&gt;
where
&lt;stx&gt;
=
Start of text character (1 digit)
&lt;id&gt;
=
Sensor identification character, for
example, A (one digit).
&lt;spd&gt;
=
Wind speed (in m/s) multiplied by 10, for
example, 045 is 4.5 m/s (three digits).
VAISALA _________________________________________________________51
User's Guide ________________________________________________________
&lt;dir&gt;
=
Wind direction with two octal numbers for
6-bit binary data, for example, 45 = 37
corresponds to 37/64*360 = 208 degrees
8
10
The WAT11 polling command is defined as follows:
&lt;esc&gt;&lt;id&gt;
where
&lt;esc&gt;
=
Escape character ASCII 27H
&lt;id&gt;
=
Sensor ID, for example, A.
Missing Readings
The WAT11 message reports missing data as slashes (/////).
NOTE
The sensor has a 20 ms timeout in receiving characters.
Therefore, polling strings should be transmitted by a
programmable device, not as a user command via terminal
sessions.
Wind Speed Units
There are four wind speed units available:
a.
Miles/hours
b.
Knots
c.
Kilometers/hours
d.
Meters/seconds
52 _____________________________________________________ M210361en-B
Chapter 4 ___________________________________________________ Operation
NOTE
When the operation mode is WAT11 (selected from the
configuration parameter 1), the only option for the wind
speed unit is meters/second as the WAT11 message does
not contain wind speed unit information.
Average Interval
The averaging interval can be selected as full seconds
between 1 and 9 seconds. For the WS425 sensor, the time
between each consecutive wind direction measurement is
one second. Each wind direction measurement taken over
the preceding averaging interval is summed and the sum is
divided by the number of measurements.
The same averaging interval is used for both the average
wind speed and average wind direction.
The sensor computes a true running average. If the data
acquisition system requests data before the initial averaging
interval completes, the sensor returns the best possible
running average.
Averaging Method
These settings affect the calculation of wind speed and
direction. The available options are as follows:
a.
Scalar averaging
b.
Vector averaging
Scalar Averaging
When the scalar averaging is selected, the wind direction is
a circular function with a discontinuity at due north, where
360&deg; is equal to 0&deg;. For example, 359&deg; + 5&deg; = + 4&deg; and
0&deg; - 5&deg; = 355&deg;.
VAISALA _________________________________________________________53
User's Guide ________________________________________________________
The microprocessor translates this circular function to a
linear function, that is, 359&deg; + 5&deg; is translated to 364&deg; and
0&deg; - 5&deg; translates to - 5&deg;.
To calculate the scalar average wind direction, each
translated wind direction measurement taken over the
preceding averaging interval is summed and the sum is
divided by the number of measurements.
Vector Averaging
Each x velocity and y velocity measurement over the
averaging interval is added and then divided by the number
of measurements. The resulting average x velocity and
average y velocity are converted to polar direction and
magnitude, returning as average direction in degrees and
speed in the chosen units.
Output Interval
The output interval can be selected in full seconds between
1 and 9 seconds. These settings are independent of the
averaging interval (configuration parameter 3, see section
Average Interval on page 53). Regardless of the length of
the output interval, the last measurement sample before
transmission is always the last sample of the averaging
window. Therefore, the transmitted data is always based on
the latest measurements.
If the output interval is set to zero (0), polling is used in data
acquisition.
NOTE
When using the NMEA Standard as the operating mode
(configuration parameter 1), there must be a non-zero
setting for output interval since polling is not supported in
the NMEA Standard mode.
54 _____________________________________________________ M210361en-B
Chapter 4 ___________________________________________________ Operation
Sensor ID Character
The sensor ID character must be a single capital letter from
A to Z. Numbers or small letters are not accepted. After an
ID is defined for a sensor, the configuration menu can be
opened by typing open &lt;id&gt;. This is useful if several
sensors are sharing the same communication line. When
running the NMEA Extended or WAT11 mode, the sensor
ID is part of the polling string.
Wind Direction Coast Threshold
At very low wind speeds, the measured wind direction is
meaningless. Therefore, you can specify a direction coast
speed. When the measured wind speed drops below the
direction coast speed, the calculations use the last wind
direction that occurred while the wind speed WS at or above
the direction coast speed to average wind direction. You can
specify a direction coast speed between 0.0 and 9.9 units of
measurement. Use 0.0 if coasting is not required.
For example, the direction coast speed = 2.0. Consecutive
measurements are as presented in Table 12 below.
Table 12
Consecutive Measurements of Wind
Direction
Measured Wind
Speed
3.5
2.5
2.2
1.9
1.2
2.1
NOTE
Measured Wind
Direction
350
340
340
175
045
345
Wind Direction Used
for Averaging
350
340
340
340 (coasting)
340 (coasting)
345
The wind direction coast threshold can be set to a non-zero
value only when the averaging method (configuration
parameter 4) is set to scalar.
VAISALA _________________________________________________________55
User's Guide ________________________________________________________
Head Orientation
The sensor can be installed either transducers up or
transducers down. The wind direction calculation requires
that the installation position is configured correctly to the
sensor.
Bit Rate
The following options are available:
- 1200b
- 2400b
- 4800b
- 9600b
- 19200b
The new bit rate setting is activated as soon as the
configuration changes are saved (selection 12) and operation
is resumed (selection 14).
NOTE
For the first 5 seconds after powering up the sensor, the
serial line parameters are 9600b, 8, N, 1.
Parity
The following options are available:
- None
- Odd
- Even
56 _____________________________________________________ M210361en-B
Chapter 4 ___________________________________________________ Operation
Data Bits
The available options are 7 or 8 data bits.
Save Configuration
After adjusting one of the configuration parameters, apply
this function to save the new settings.
Zero Speed Calibration
The zero speed calibration is done to all sensors in the
factory before delivery. There is no reason to perform this
tuning periodically. Instead, use the margin verifier for
periodic testing as described in section Periodic Testing on
page 81. Do the zero speed calibration only after possible
firmware update or if the periodic test indicates too high
wind speeds.
To perform the zero speed calibration, do the following:
CAUTION
1.
Remove the bird spikes and install the verifier as
described in Figure 13 on page 82.
2.
Select zero speed calibration from the configuration
menu and wait until the sensor resumes to normal
operation.
3.
Check that the sensor passes the periodic test.
Do not perform the zero speed calibration unless the
margin verifier is mounted on the sensor. Use this function
only if you suspect that the sensor characteristics have
changed.
VAISALA _________________________________________________________57
User's Guide ________________________________________________________
Resume Operation
After opening the configuration menu, return to the current
mode of operation by selecting &quot;Resume Operation&quot;. This
selection terminates the configuration dialog.
NOTE
Changes to the configuration will not be saved
automatically. Use the SAVE CONFIGURATION
command to save the changes.
SDI-12 Protocol
SDI-12 is a standard for interfacing data recorders with
microprocessor-based sensors. The name stands for
serial/digital interface at 1200 baud. SDI-12 is intended for
applications with the following requirements:
- Battery-powered operation with minimal current drain.
- Low system cost.
- Use of a single data recorder with multiple sensors on one
cable.
- Up to 200 feet (60 meters) of cable between a sensor and
a data recorder.
SDI-12 Support Group
The SDI-12 Support Group is an association of companies
that produce and use SDI-12 products with the purpose of
reviewing requests to enhance, clarify, or modify the
SDI-12 architecture and that votes on proposed changes to
SDI-12. More information of the group, as well as the
complete SDI-12 standard text is available from the SDI-12
web-site in the following address: www.sdi-12.org/.
58 _____________________________________________________ M210361en-B
Chapter 4 ___________________________________________________ Operation
SDI-12 Electrical Interface
The SDI-12 electrical interface uses the SDI-12 bus to
transmit serial data between SDI-12 data recorders and
sensors. The SDI-12 bus is the cable that connects multiple
SDI-12 devices. This is a cable with three conductors:
- A serial data line
- A ground line
- A 12-volt line
NOTE
With Vaisala SDI-12 cable, code WS425CAB SDI the lead
colors are as follows: data - whi/yel; ground - Blk; and 12volts - Brn.
The SDI-12 bus is can have at least 10 sensors connected to
it. The bus topology is a parallel connection, where each of
the 3 wires of different sensors are connected in parallel.
Serial Data Line
The data line is a bi-directional, three-state, data transfer
line. Table 13 below shows the logic and voltage levels for
the transmission of serial data for the SDI-12 standard. The
data line uses negative logic.
Table 13
Condition
Marking
Spacing
Transition
Logic and Voltage Level for Serial Data
Binary State
1
0
Undefined
Voltage Range
-0.5 to 1.0 volts
3.5 to 5.5 volts
1.0 to 3.5 volts
Voltage Transitions
During normal operation, the data line voltage slew rate
must not be greater than 1.5 volts per microsecond.
VAISALA _________________________________________________________59
User's Guide ________________________________________________________
Impedance
When an SDI-12 device has its transmitter on, its direct
current (DC) source resistance must be greater than 1000
ohms and less than 2000 ohms. When the transmitter of any
SDI-12 device is off, or in a low-power standby mode, the
DC resistance to ground must be within 160 K to 360 K
ohms. If an SDI-12 sensor does not use the 12-volt line for
power, its data line resistance to ground while powered
down must be within 160 K to 360 K ohms.
SDI-12 Communications
Protocol
SDI-12 data recorders and sensors communicate by an
exchange of ASCII characters on the data line. The data
recorder sends a break to wake up the sensors on the data
line. A break is continuous spacing on the data line for at
least 12 milliseconds. The data recorder then sends a
command. The sensor, in turn, returns the appropriate
response. Each command is for a specific sensor. The first
character of each command is a unique sensor address that
specifies with which sensor the recorder wants to
communicate. Other sensors on the SDI-12 bus ignore the
command and return to low-power standby mode. When a
data recorder tells a sensor to start its measurement
procedure, the recorder does not communicate with any
other sensor until the data collection from the first sensor is
complete.
A typical recorder/sensor measurement sequence proceeds
in the following order:
1.
The data recorder wakes all sensors on the SDI-12 bus
with a break.
2.
The recorder transmits a command to a specific,
addressed sensor, instructing it to make a
measurement.
60 _____________________________________________________ M210361en-B
Chapter 4 ___________________________________________________ Operation
3.
The addressed sensor responds within 15.0
milliseconds returning the maximum time until the
measurement data will be ready and the number of data
values it will return.
4.
If the measurement is immediately available, the
recorder transmits a command to the sensor instructing
it to return the measurement(s). If the measurement is
not ready, the data recorder waits for the sensor to send
a request to the recorder, which indicates that the data
is ready. The recorder then transmits a command to get
the data.
5.
The sensor responds, returning one or more
measurements.
Baud Rate and Byte Frame
Format
The baud rate for SDI-12 is 1200 b. Table 14 below shows
the byte frame format for SDI-12.
Table 14
Byte Frame Format for SDI-12
1 start bit
7 data bits, least significant bit transmitted first
1 parity bit, even parity
1 stop bit
Two Different Submodes
Vaisala WS425 is designed to work in two different
operational modes when running the SDI-12 protocol. These
modes will be called &quot;submode A&quot; and &quot;submode B&quot;. This
arrangement makes it possible to do the following:
- Keep the sensor in a sleep mode when measurement is
not active, thus enabling a very low-power operation of
the sensor (submode A).
- Initiate periods where continuous measurement is made.
Long averages (up to 1 hour) of wind speed and direction,
VAISALA _________________________________________________________61
User's Guide ________________________________________________________
as well as gust data is available during this period
(submode B).
As a default, the sensor runs in submode A. Specific
commands can be issued in order to:
- Set the sensor into submode B and initiate continuous
measurement.
- Collect averaged data in submode B.
- Force the sensor back to submode A.
If a sensor is not forced back to the low-power submode A
by the data logger, the sensor will eventually do this
independently after two hours have elapsed. The timing
diagram is illustrated in Table 15 below.
Table 15
Data Logger Time
Command
[s]
SDI Timing Chart
Sensor Response
Comment
(Sensor in submode A.)
aXQx;c.c;yyy
y!
0
a&lt;cr&gt;&lt;lf&gt;
Place sensor into
submode B. yyyy is the
averaging time.
(Sensor in submode B.)
aR0!
h
a&lt;WS&gt;&lt;WD&gt;&lt;GS&gt;&lt;G
D&gt;&lt;cr&gt;&lt;lf&gt;
Continuous
measurements (if time is
shorter than yyyy, only
partial data is available).
(Sensor in submode B.)
aXS!
a&lt;cr&gt;&lt;lf&gt;
Force the sensor back to
submode A.
(Sensor in submode A.)
3600
If aXS! was not given, the
timer resets the sensor to
submode A.
62 _____________________________________________________ M210361en-B
Chapter 4 ___________________________________________________ Operation
Standard SDI-12 Commands
Supported by WS425
Acknowledge Active Command (a!)
This command is used to ensure that a sensor is responding
to a data recorder or another SDI-12 device. It asks a sensor
to acknowledge its presence on the SDI-12 bus.
The command is the following:
a!
where
a
!
= The sensor address.
= Terminates the command.
The response is the following:
a&lt;CR&gt;&lt;LF&gt;
where
a
= The sensor address. The default values is
zero (0).
&lt;CR&gt;&lt;LF&gt; = Terminates the response.
The following is an example of the command:
0!
The following is an example of the response:
0&lt;CR&gt;&lt;LF&gt;
VAISALA _________________________________________________________63
User's Guide ________________________________________________________
Send Identification Command (aI!)
This command is used to query sensors for their SDI-12
compatibility level, model number, and firmware version
number.
The following is an example of the command:
aI!
where
a
I
!
= The sensor address.
= The send identification command
= Terminates the command.
The following is an example of the response:
allccccccccmmmmmmvvvxxx . . . xxx&lt;CR&gt;&lt;LF&gt;
where
a
ll
= The sensor address.
= The SDI-12 version number, indicating
SDI-12 version compatibility; for
example, version 1.1 is encoded as 11.
cccccccc
= An 8-character vendor identification
Vaisala_
mmmmmm = 6 characters specifying the sensor model
number WS425.
vvv
= 3 characters specifying the firmware
version 604.
For
= An optional field, up to 13 characters,
example,
used for a serial number or other specific
xxx ... xx
sensor information that is not relevant for
operation of the data recorder (not used).
&lt;CR&gt;&lt;LF&gt; = Terminates the response.
64 _____________________________________________________ M210361en-B
Chapter 4 ___________________________________________________ Operation
Address Query Command (?!)
When a question mark (?) is used as the address character
with the acknowledge active command (a!), the sensor will
respond as if it is being addressed on the SDI-12 bus. For
example, if a sensor detects ?!, it will respond with
a&lt;CR&gt;&lt;LF&gt;, no matter what its address may be. This will
allow a user to determine the address of a sensor. The user
should understand that if more than one sensor is connected
to the bus, they will all respond, causing a bus contention.
The command is the following:
?!
where
?
!
= Wildcard.
= Terminates the command.
The response is the following:
a&lt;CR&gt;&lt;LF&gt;
where
a
= The sensor address.
&lt;CR&gt;&lt;LF&gt; = Terminates the response.
Change Address Command (aAb!)
This command changes the address of a sensor. After this
command has been issued and responded to, the sensor is
not required to respond to another command for one second.
This gives the sensor time to write the new address to nonvolatile memory.
VAISALA _________________________________________________________65
User's Guide ________________________________________________________
The command is the following:
aAb!
where
a
A
b
!
=
=
=
=
The sensor address.
The change address command.
The address to change to.
Terminates the command.
The response is the following:
b&lt;CR&gt;&lt;LF&gt;
where
b
= The address of the sensor (will equal the
new address or the original address if
the sensor is unable to change the
address).
&lt;CR&gt;&lt;LF&gt; = Terminates the response.
Start Measurement Command (aM!)
With this command, the sensor will make a measurement.
The sensor will not return the measurement to the data
recorder after this command. It shows the time after which
the measurement result can be retrieved using the D0!
command and it also shows the number of parameters. The
following is an example:
&gt;0M!
00015
The SEND DATA (D0!) command must be issued to get
the measurements.
66 _____________________________________________________ M210361en-B
Chapter 4 ___________________________________________________ Operation
The command is the following:
aM!
where
a
M
!
= The sensor address.
= The start measurement.
= Terminates the command.
The response is the following:
atttn&lt;CR&gt;&lt;LF&gt;
where
a
ttt
= The sensor address.
= The specified time, in seconds, until the sensor
will have the measurement ready (001).
n
= The number of measurement values the sensor
will make and return in one or more
subsequent D commands (5).
&lt;CR&gt;&lt;LF&gt; = Terminates the response.
Send Data Command (aD0!)
This command is used to get instant data from the sensor.
D0! must be preceded with an M! command or an V!
command. The sensor responds by sending measurement
data (after M!) or verification data (after V!).
In a SDI-12 system compliant with the standard, if the
expected number of measurements is not returned in
response to a D0! command, a data recorder issues D1!,
D2!, and so on until all measurement values are received.
The expected number of measurements is the one that WS
received by the data recorder in response to an M! or V!
VAISALA _________________________________________________________67
User's Guide ________________________________________________________
command. Multiple data requests are not needed with
WS425, since all return values fit easily into one response
string.
The command is the following:
aD0!
where
a
D0
!
= The sensor address.
= The send data command.
= Terminates the command.
When the previous command WS aM! is given, the
response is the following:
a&lt;WS&gt;&lt;WD&gt;&lt;x&gt;&lt;y&gt;&lt;s&gt;&lt;CR&gt;&lt;LF&gt;
where
a
&lt;WS&gt;
= The sensor address.
= Polar wind speed in selected units,
format: +(ss)s.s
&lt;WD&gt;
= Polar wind direction in degrees, format
+(dd)d
&lt;x&gt;
= x component of wind speed in selected
units, format: &plusmn;(ss)s.s
&lt;y&gt;
= y component of wind speed in selected
units, format: &plusmn;(ss)s.s
&lt;s&gt;
= Static speed of sound in mph, format:
&plusmn;(ss)s.s
&lt;CR&gt;&lt;LF&gt; = Terminates the response.
The above are measurement data fields.
68 _____________________________________________________ M210361en-B
Chapter 4 ___________________________________________________ Operation
When the previous command WS aV! is given, the response
is the following:
a&lt;watchdog&gt;&lt;WS_unit&gt;&lt;SDI-mode&gt;&lt;spare&gt;&lt;CR&gt;&lt;LF&gt;
where
a
= The sensor address.
&lt;watchdog&gt; = The number of times the watchdog has
triggered. Ideally should be zero. Format:
+(c)c
&lt;WS_unit&gt; = Wind speed unit. The options are:
+0 = mph
+1 = kt
+2 = km/h
+3 = m/s
&lt;SDI= Current submode setting. The options are:
mode&gt;
+0 = SDI-12 submode A
+1 = SDI-12 submode B
&lt;spare&gt;
= 1 digit for factory use, format: +c
&lt;CR&gt;&lt;LF&gt; = Terminates the response.
The above are verification data fields.
Continuous Measurements (aR0!)
A sensor that is able to continuously monitor the
phenomena to be measured, does not require a start
measurement command (M!). The data can be read directly
with the R0! command.
WS425 uses this command when the sensor is set to work in
SDI-12 submode B. The command retrieves averaged wind
data and gust wind data. The averaging time window is
selectable between 3 and 3600 seconds.
VAISALA _________________________________________________________69
User's Guide ________________________________________________________
The command is the following:
aR0!
where
a
R0
!
= The sensor address.
= The send continuous measurements
command.
= Terminates the command.
The response is the following:
a&lt;WS_ave&gt;&lt;WD_ave&gt;&lt;GS&gt;&lt;GD&gt;&lt;CR&gt;&lt;LF&gt;
where
a
&lt;WS_ave&gt;
= The sensor address.
= Average wind speed over the past yyyy1
seconds in currently active units. Format:
+(ss)s.s
&lt;WD_ave&gt; = Average wind direction over the past
yyy1 seconds in degrees. Format +(dd)d
&lt;GS&gt;
= Gust wind speed; the highest n1
measurement running average during the
past yyyy1 seconds, in currently active
units. Format: +(ss)s.s
&lt;GD&gt;
= Gust direction; n1 second average over
the same time period as the gust speed.
Format: +(dd)d.
&lt;CR&gt;&lt;LF&gt; = Terminates the response.
1)
The parameters yyyy and n are issued to the sensor as a part of the
&quot;Place sensor in submode B (aXQx;c.c;n;yyyy!)&quot; command. This
command must be given to the sensor before aR0!. See the command
description for aXQ...! for full description of the parameters.
70 _____________________________________________________ M210361en-B
Chapter 4 ___________________________________________________ Operation
Start Verification (aV!)
This command tells the sensor to return a verification in
response to a following D0! command. The WS425
verification data includes a watchdog count, sensor
measurement unit settings and the current SDI mode setting.
The command is the following:
aV!
where
a
V
!
= The sensor address.
= The start verification command.
= Terminates the command.
The response is the following:
attn&lt;CR&gt;&lt;LF&gt;
where
a
tt
= The sensor address.
= The time in seconds the sensor needs
until it has the verification data ready
(01)
n
= The number of verification data fields
that will be returned (4).
&lt;CR&gt;&lt;LF&gt; = Terminates the response.
VAISALA _________________________________________________________71
User's Guide ________________________________________________________
Vaisala-specific SDI-12
Commands Supported by
WS425
Measurement Unit Change (aXUx!)
This command sets the desired measurement unit for wind
speed. The command is available in submode A only.
The command is the following:
aXUx!
where
a
XU
x
!
= The sensor address.
= The change measurement unit command.
= Desired wind speed unit. The options are:
0 = mph (default value)
1 = kt
2 = km/h
3 = m/s
= Terminates the command.
The response is the following:
a+x&lt;CR&gt;&lt;LF&gt;
where
a
= The sensor address.
x
= The new wind speed setting.
&lt;CR&gt;&lt;LF&gt; = Terminates the response.
72 _____________________________________________________ M210361en-B
Chapter 4 ___________________________________________________ Operation
Heater Control Command (aXHx!)
This command switches the sensor heating into active or
disabled state. In the active state, heating is still
thermostatically controlled. The command works only for
heated sensor models.
The command is the following:
aXHx!
where
a
XH
x
!
= The sensor address.
= The heater control command.
= The options are:
0 = disable the heater
1 = enable the heater
= Terminates the command.
The response is the following:
a&lt;CR&gt;&lt;LF&gt;
where
a
= The sensor address.
x
= The new wind speed setting.
&lt;CR&gt;&lt;LF&gt; = Terminates the response.
VAISALA _________________________________________________________73
User's Guide ________________________________________________________
Check Current Submode (aX?!)
The command is the following:
aX?!
where
a
X?
!
= The sensor address.
= The check current submode command.
= Terminates the command.
The response is the following:
a+x&lt;CR&gt;&lt;LF&gt;
where
a
x
= The sensor address.
= The currently active submode. The
options are:
0 = submode A
1 = submode B
&lt;CR&gt;&lt;LF&gt; = Terminates the response.
Place Sensor in Submode B
(aXQx;c.c;n;yyyy!)
This command sets the sensor into submode B which
enables calculation of averaged wind data and gust wind
speed and direction.
The command is the following:
aXQx;c.c;n;yyyy!
74 _____________________________________________________ M210361en-B
Chapter 4 ___________________________________________________ Operation
where
a
XQ
x
c.c
n
yyyy
!
= The sensor address.
= The place sensor in submode B command.
= The desired wind averaging method. The
options are:
0 = use scalar averaging
1 = use vector averaging
= The wind direction coasting threshold in
the current wind speed units. The coasting
can only be used with scalar averaging.
= The number of samples that form the gust
wind speed and direction value (1 Hz
sampling). The valid range is 1 to 9.
= The length of averaging window [s]
= Terminates the command.
The response is the following:
a&lt;CR&gt;&lt;LF&gt;
where
a
= The sensor address.
&lt;CR&gt;&lt;LF&gt; = Terminates the response.
Reset the Sensor to Submode A Command
(aXS!)
When the sensor is set to submode B in order to compute
averaged wind data, the sensor will stay in mode B until a
2-hour time period has elapsed. This computation period can
be aborted earlier by issuing the command (XS!).
The command is the following:
aXS!
VAISALA _________________________________________________________75
User's Guide ________________________________________________________
where
a
XS
!
= The sensor address.
= The reset sensor to submode A command.
= Terminates the command.
The response is the following:
a&lt;CR&gt;&lt;LF&gt;
where
a
= The sensor address.
&lt;CR&gt;&lt;LF&gt; = Terminates the response.
Check Current Measurement Unit (aX*!)
The command is the following:
aX*!
where
a
X*
!
= The sensor address.
= The check current measurement unit
command.
= Terminates the command.
The response is the following:
a+x&lt;CR&gt;&lt;LF&gt;
76 _____________________________________________________ M210361en-B
Chapter 4 ___________________________________________________ Operation
where
a
x
= The sensor address.
= Currently active wind speed unit. The
options are:
0 = mph
1 = kt
2 = km/h
3 = m/s
&lt;CR&gt;&lt;LF&gt; = Terminates the response.
SDI-12 TIMING
The Figure 12 on page 78 shows a timing diagram for an
SDI-12 command and its response. The tolerance for all
SDI-12 timing is &plusmn;0.40 milliseconds. The only exception to
this is the time between the stop bit of one character and the
start bit of the next character. The maximum time for this is
1.66 milliseconds, with no tolerance.
- A data recorder transmits a break by setting the data line
to spacing for at least 12 milliseconds.
- The sensor will not recognize a break condition for a
continuous spacing time of less than 6.5 milliseconds.
The sensor will always recognize a break when the line is
continuously spacing for more than 12 milliseconds.
- When receiving a break, a sensor must detect 8.33
milliseconds of marking on the data line before it looks
for an address.
- A sensor must wake up from a low-power standby mode
and be capable of detecting a start bit from a valid
command within 100 milliseconds after detecting a break.
- After a data recorder transmits the last character of a
command, it must relinquish control of the data line
within 7.5 milliseconds following the end of the stop bit.
(Tolerance: +0.40 milliseconds.)
VAISALA _________________________________________________________77
User's Guide ________________________________________________________
DATA
break
(at least 12
milliseconds)
SDI-12
Data
SENSO
response
command
marking
(at least 8.33
milliseconds)
marking
(at least 8.33
milliseconds)
sensor must respond
within 15
maximum time
380 ms most commands
780ms D0,R0 commands
Figure 12 Timing Diagram
- After receiving the break and the command, the
addressed sensor sets the data line to marking at 8.33
milliseconds and then send the response. (Tolerance: 0.40 milliseconds.) The start bit of the first response byte
must start within 15 milliseconds after the stop bit of the
last byte of the command. (Tolerance: +0.40
milliseconds.)
- After a sensor transmits the last character of a response, it
must relinquish control of the data line within 7.5
milliseconds. (Tolerance: +0.40 milliseconds.)
- No more than 1.66 milliseconds of marking are allowed
between the end of the stop bit and the start bit (e.g.,
between characters) on any characters in the command or
the response. (No tolerance.) This permits a response to
an M command to be sent within a
380-millisecond window.
- Sensors must return to a low-power standby mode after
receiving an invalid address or after detecting a marking
state on the data line for 100 milliseconds. (Tolerance:
+0.40 milliseconds.)
78 _____________________________________________________ M210361en-B
Chapter 4 ___________________________________________________ Operation
- When a recorder addresses a different sensor, or if the
data line has been in the marking state for more than 87
milliseconds, the next command must be preceded by a
break.
NOTE
In addition to being a power consumption state, the low
power standby mode is a protocol state and a break is
required to leave that state.
VAISALA _________________________________________________________79
User's Guide ________________________________________________________
This page intentionally left blank.
80 _____________________________________________________ M210361en-B
Chapter 5 ________________________________________________ Maintenance
CHAPTER 5
MAINTENANCE
Periodic Testing
Section Measuring Principle on page 17 explains that the
sensor measures how long it takes for an ultrasonic signal to
travel from transmitter to receiver. Therefore, the accuracy
of the sensor depends on the accuracy of two factors:
- The distance between the ultrasonic transmitter and
receiver. This requires a measurement of the transducer
arm trueness.
- The time-of-flight measurement circuit, which uses a
crystal oscillator for its time reference.
NOTE
The crystal oscillator is used by the communications circuit
for the bit rate generator. If you use the serial
communication modes and the oscillator loses accuracy, the
sensor stops communicating. Thus, the sensor cannot send
erroneous values produced by faulty timing.
If you use the RS-232 operational modes, perform periodic
testing to detect slow deterioration of the sensor before it
significantly affects accuracy. Perform the test either in the
field or in a laboratory. The periodic test uses the verifier,
which is a small echo-free chamber . The verifier is shown
in Figure 13 on page 82.
VAISALA _________________________________________________________81
User's Guide ________________________________________________________
The test consists of the following steps:
NOTE
1.
Slip the verifier over the three transducers (see Figure
13 below).
2.
In outdoor conditions, secure the zero wind flow by
covering the sensor and verifier.
3.
The sensor must read less than 0.5 miles per hour
(0.22 m/s) with the verifier in place.
Some random data samples may be lost during the zero
verifier test. This, however, does not indicate that the
sensor is faulty.
0003-016
Figure 13 Verifier
82 _____________________________________________________ M210361en-B
Chapter 6 ______________________________________________ Troubleshooting
CHAPTER 6
TROUBLESHOOTING
Common Problems
Frequently Asked Questions
(FAQ)
Q = Question
A= Answer
Q:
I am looking for mounting options/products for the WS425
Ultrasonic Wind Sensor. Preferably, a tripod mount. If none
is available, are there CAD files so we can design a tripod to
fit this sensor?
A:
A drawing of an optional sensor adapter is included in
Chapter 3 section Installation Procedure on page 25. This
adapter fits onto an 1&quot; IPS standard pipe. Following the
dimensions of the adapter, you may prefer to design your
own sensor mounting. See also a dimensional drawing of
the sensor in Appendix A on page 91. Please make sure that
no obstacles are near the sensor, especially at the level of
the ultrasonic transducers.
VAISALA _________________________________________________________83
User's Guide ________________________________________________________
Q:
We intend to install a WS425 to a radio link tower. Is the
sensor sensitive to RF frequencies generated by GSM link
antennas ?
A:
A radio link tower is an extremely demanding RF
environment for any measurement device. The WS425
sensor has undergone electromagnetic compatibility tests in
two different laboratories and is compliant with
requirements of MIL-STD-461B and EN 61000-4-3. The
tested frequency range spanned from 10 kHz to 10 GHz.
The tested sensors were only disturbed by frequencies
occurring at the band from 95kHz to 107kHz, which is the
range that the sensor uses for the ultrasonic measurement.
Radio communication devices do not operate at this band.
Despite the heavy testing, the GSM link equipment may
cause interference to an ultrasonic sensor due to extremely
high electromagnetic field levels around the transmission
antenna. In this type of installation, a small displacement of
the sensor may completely remove an interference problem
that occurs at a certain point of the mast. Trial and error is
really the only way of finding out whether RF disturbance
will be an issue.
Q:
I have tried out my WS425. When I turn the power on the
sensor is not sending any data. I used an RS232C checker
but the Tx line is not active (no data is coming to my PC).
A:
By default, the sensor is set to a command-response mode
(polling mode). This means that the sensor is waiting for a
data request command from the data logger. If you want the
sensor to automatically send data through the serial line, you
need to open a maintenance connection to your WS425
sensor and configure parameter number 5, Output Interval,
84 _____________________________________________________ M210361en-B
Chapter 6 ______________________________________________ Troubleshooting
to have a non-zero value. In order to open a maintenance
connection, see the attached procedure on the next page.
Instructions for Opening a
Serial Terminal Connection to
WS425
1.
Connect an RS-232 cable between your terminal
computer, power supply and your sensor. If you are
using a Vaisala
RS-232 cable with code ZZ45203, the cable colors are
the following:
Connections to power supply:
Black (WS425 pin 1)
Brown (WS425 pin 11)
-
Ground
+12 VDC
Connections to terminal PC:
Red (WS425 pin 9) Blu (WS425 pin 10) Yellow (WS425 pin 8) -
RxD (PC 9-pin serial
port, pin n:o 2)
TxD (PC 9-pin serial
port, pin n:o 3)
GND (PC 9-pin serial
port, pin n:o 5)
2.
Open the Windows HyperTerminal program. From
HyperTerminal, select File - Properties and click
Configure. Set communication parameters 9600,8,N,1
and Flow Control as None.
3.
From HyperTerminal, select View - Font. Set Font as
Terminal.
4.
Select Call - Disconnect. Then select Call - Connect.
5.
Switch the sensor power supply on and off. Make sure
that the sensor is completely powered down before
reconnecting the power supply (Many power supplies
VAISALA _________________________________________________________85
User's Guide ________________________________________________________
store energy and need time to be discharged
completely). During the first 5 seconds after the sensor
starts up, the serial line settings will remain as 9600, 8,
N, 1. After this, the programmed communication
parameters will become effective.
You have 5 seconds time to type: open&lt;Enter&gt;
Make sure that the sensor is already on when you type
the first letter. If you do not succeed, try several times
and check your connections.
6.
After a successful OPEN command, the sensor should
display a configuration menu. You can now adjust the
settings.
Technical Support
For technical questions, contact the Vaisala technical
support:
E-mail
Phone (int.)
Fax
[email protected]
+358 9 8949 2789
+358 9 8949 2790
Return Instructions
If the product needs repair, please follow the instructions
below to speed up the process and avoid extra costs.
1.
Read the warranty information.
2.
Write a Problem Report with the name and contact
information of a technically competent person who can
provide further information on the problem.
3.
On the Problem Report, please explain:
- What failed (what worked / did not work)?
- Where did it fail (location and environment)?
86 _____________________________________________________ M210361en-B
Chapter 6 ______________________________________________ Troubleshooting
- When did it fail (date, immediately / after a while /
periodically / randomly)?
- How many failed (only one defect / other same or
similar defects / several failures in one unit)?
- What was connected to the product and to which
connectors?
- Input power source type, voltage and list of other
items (lighting, heaters, motors etc.) that were
connected to the same power output.
- What was done when the failure was noticed?
4.
Include a detailed return address with your preferred
shipping method on the Problem Report.
5.
Pack the sensor into the original shipping container.
The sensor warranty will be void if another packing
method is used.
6.
Send the box to the nearest Vaisala Service depot:
European Service Center:
Vaisala Service
Vanha Nurmij&auml;rventie 21
01670 Vantaa
FINLAND
Phone: +358 9 89492758
Fax: +358 9 89492295
E-mail: [email protected]
American Service Center:
Vaisala Inc.
100 Commerce Way
Woburn MA 01801-1068
USA
Phone: +10888 VAISALA; +1 781 9334500
Fax: +1 781 9338029
E-mail: [email protected]
VAISALA _________________________________________________________87
User's Guide ________________________________________________________
Asian Service Center:
Vaisala KK
42 Kagurazaka 6-Chome
Shinjuku-ku
Tokyo 162-0825
JAPAN
Phone: +813 32669611
Fax: +813 32669610
E-mail: [email protected]
88 _____________________________________________________ M210361en-B
Chapter 7 _______________________________________________ Technical Data
CHAPTER 7
TECHNICAL DATA
Specifications
Table 16
Wind Speed
Measurement range
serial output
analog output
Starting threshold
Delay distance
Resolution
Accuracy (range 0 ... 65 m/s)
Wind Direction
Measurement range
Starting threshold
Delay distance
Resolution
Accuracy (wind speed over 1 m/s)
Outputs
Digital outputs
type
bit rate
available averages
SDI12- Standard Data Interface
type
bit rate
available averages
Technical Specifications
0 ... 65 m/s (0 ... 144 mph, 0 ... 125 knots)
0 ... 56 m/s (0 ... 124 mph, 0 ... 107 knots)
virtually zero
virtually zero
0.1 m/s (0.1 mph, 0.1 knots, 0.1 km/h)
&plusmn;0.135 m/s (0.3 mph, 0.26 knots) or 3 % of
reading, whichever is greater
0 ... 360&deg;
virtually zero
virtually zero
1&deg;
&plusmn;2&deg;
RS232, RS422 or RS485, four different
message formats
adjustable from 1200 to 19200 bit/s
RS232: 1 to 9 seconds
3 wires for ground, signal and supply
fixed 1200 bit/s
1 to 3600 seconds
VAISALA _________________________________________________________89
User's Guide ________________________________________________________
Wind Speed
Analog outputs
wind speed
frequency
voltage
output impedance
wind direction
simulated potentiometer
reference voltage
output impedance
Response Characteristics
Maximum reading rate
Sonic measurement time
Signal processing time
Response time
General
Operating power supply
and for heated model
Operating temperature
WS425 non-heated
WS425 heated
Material
body
sensor arms
transducer heads
Dimensions
5 Hz/mph
8.0 mV/mph
10 kohm
0 ...Vref represents 0 ... 359&deg;
1.0 ... 4.0 V
24 kohm
1 per second
0.2 s
0.15 s
0.35 s
10 ...15 VDC, 12mA typical (analog)
36 VDC &plusmn;10 %, 0.7 A
-40 ... +55 &deg;C (-40 ... +131 &deg;F)
-55 ... +55 &deg;C (-67 ... +131 &deg;F)
stainless steel
stainless steel
silicone rubber and PVC
Height
Width
355 mm 250 mm
14&quot;
10&quot;
Depth
286 mm
12&quot;
Weight
WS425 stainless steel
1.7 kg (3.7 lbs)
Complies with EMC standard EN61326-1:1997 + Am1: 1998; Generic Environment
Accessories
Cable supporting analog outputs, 10 m ZZ45204
Cable supporting RS-232 outputs, 10 ZZ452203
m
Cable supporting RS-485/422 outputs, 010411
10 m
Cable supporting SDI-12 outputs, 10
WS425CABSDI
m
Adapter for 30 - 35 mm
WS425FIX30
(11/4&quot;) diameter vertical tube
Adapter for 60 mm
WS425FIX60
(21/4&quot;) diameter vertical tube
Field verifier
WS425VERIFIER
90 _____________________________________________________ M210361en-B
Appendix A ______________________________________________ Technical Data
APPENDIX A
0212-043
Figure 14 WS425FIX30 Adapter
VAISALA _________________________________________________________91
User's Guide ________________________________________________________
0301-012
Figure 15 WS425FIX60 Adapter
92 _____________________________________________________ M210361en-B
Appendix A ______________________________________________ Technical Data
0301-013
Figure 16 WS425FIX60 Adapter
The following numbers refer to Figure 16 above.
1=
2=
3=
4=
Adapter tube
Fastening clamp
Fastening bolt
Allen key
VAISALA _________________________________________________________93
">
Hello! I am an AI chatbot specifically trained to assist you with the Vaisala WS425 Ultrasonic Wind Sensor User's Guide. I have thoroughly reviewed the document and can help you locate the exact information you need or explain the content in clear and simple terms. Whether you’re looking for guidance on specific features, troubleshooting steps, or general usage, feel free to ask your questions. The more details you provide about your concerns or needs, the more accurately and effectively I can assist you!
Hide related prompts
Assistant typing
Assistant terminated
Key Features

Measures wind speed and direction
Uses ultrasonic technology
Accurate and reliable
Operates in various modes
Supports multiple communication protocols
Provides averaging functionality
Frequently Answers and Questions

What is the principle of operation for the WS425 Ultrasonic Wind Sensor?

The sensor measures the time it takes ultrasound to travel between transducers. The transit time is affected by wind speed, allowing the sensor to calculate both wind speed and direction.
Can I use the WS425 in a location prone to turbulence?

Ideally, the sensor should be installed in a location free from turbulence caused by nearby objects. While it is possible to install the sensor in a turbulent area, the accuracy of the measurements may be affected.
How to align WS425 correctly?

Align the wind sensor with the help of a compass. The sensor should be positioned so that the transducers marked with N and S are exactly aligned to North and South.