User manual VAISALA WS425

[. . . ] USER'S GUIDE Vaisala WINDCAP® Ultrasonic Wind Sensor WS425 M210361EN-D PUBLISHED BY Vaisala Oyj P. O. Box 26 FI-00421 Helsinki Finland Phone (int. ): +358 9 8949 1 Fax: +358 9 8949 2227 Visit our Internet pages at http://www. vaisala. com/ © Vaisala 2009 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. 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. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [. . . ] Thus, polling strings should be transmitted by a programmable device, not as a user command via terminal sessions. 44 __________________________________________________________________ M210361EN-D Chapter 4 ________________________________________________________________ Operation In NMEA Extended Message, the polling can be done using the following command: $WIP<id>Q, *<chk><cr><lf> where $WIP <id> Q * <chk> <cr> <lf> = = = = = = = Fixed text Is the data ID; A . . . Z Fixed text Fixed text Checksum (8-bit XOR, excluding $ and *) Carriage return code, ASCII 0DH Line feed code, ASCII 0AH Table 11 ID Character <id> A B C D E F G H I J K L M N O Checksum Table Checksum <chk> Polling String 72 71 70 77 76 75 74 7B 7A 79 78 7F 7E 7D 7C $WIPAQ, *72<cr><lf> $WIPBQ, *71<cr><lf> $WIPCQ, *70<cr><lf> $WIPDQ, *77<cr><lf> $WIPEQ, *76<cr><lf> $WIPFQ, *75<cr><lf> $WIPGQ, *74<cr><lf> $WIPHQ, *7B<cr><lf> $WIPIQ, *7A<cr><lf> $WIPJQ, *79<cr><lf> $WIPKQ, *78<cr><lf> $WIPLQ, *7F<cr><lf> $WIPMQ, *7E<cr><lf> $WIPNQ, *7D<cr><lf> $WIPOQ, *7C<cr><lf> NOTE 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. VAISALA _______________________________________________________________________ 45 USER'S GUIDE____________________________________________________________________ WAT11 Message The fixed length format of the WAT11 message is defined as follows: <stx><id><spd><dir> where <stx> <id> <spd> <dir> = = = = Start of text character (1 digit) Sensor identification character, for example, A (one digit). Wind speed (in m/s) multiplied by 10, for example, 045 is 4. 5 m/s (three digits). Wind direction with two octal numbers for 6-bit binary data, for example, 458 = 3710 corresponds to 37/64*360 = 208 degrees The WAT11 polling command is defined as follows: <esc><id> where <esc> <id> = = Escape character ASCII 27H 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. 46 __________________________________________________________________ M210361EN-D Chapter 4 ________________________________________________________________ Operation Wind Speed Units There are four wind speed units available: a. Miles/hours Knots Kilometers/hours Meters/seconds 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. 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. Scalar averaging 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° is equal to 0°. For example, 359° + 5° = + 4° and 0° - 5° = 355°. VAISALA _______________________________________________________________________ 47 USER'S GUIDE____________________________________________________________________ The microprocessor translates this circular function to a linear function, that is, 359° + 5° is translated to 364° and 0° - 5° translates to - 5°. 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 47). 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. Sensor ID Character The sensor ID character must be a single capital letter from A to Z. After an ID is defined for a sensor, the configuration menu can be opened by typing open <id>. 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. 48 __________________________________________________________________ M210361EN-D Chapter 4 ________________________________________________________________ Operation Wind Direction Coast Threshold At very low wind speeds, the measured wind direction is meaningless. [. . . ] 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, to have a non-zero value. In order to open a maintenance connection, see the attached procedure on the next page. 74 __________________________________________________________________ M210361EN-D Chapter 6 ___________________________________________________________ Troubleshooting 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: RxD (PC 9-pin serial port, pin n:o 2) Blu (WS425 pin 10) TxD (PC 9-pin serial port, pin n:o 3) Yellow (WS425 pin 8) GND (PC 9-pin serial port, pin n:o 5) Open the Windows HyperTerminal program. [. . . ]