User manual VAISALA WMT50

[. . . ] USER'S GUIDE Vaisala WINDCAP® Ultrasonic Wind Sensor WMT50 M210736EN-B PUBLISHED BY Vaisala Oyj P. O. Box 26 FIN-00421 Helsinki Finland Visit our Internet pages at http://www. vaisala. com/ © Vaisala 2006 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. [. . . ] Also the power consumption between the measurements is about three times that of the Native mode. Address Query Command (?) This command is used to query the address of the device on the bus. If more than one sensor is connected to the bus, they will all respond, causing a bus collision. = = Address query command Command terminator VAISALA _______________________________________________________________________ 59 User's Guide ______________________________________________________________________ The response: a<cr><lf> where a <cr><lf> = = Device address (default = 0) Response terminator Example (device address 0): ?!0<cr><lf> Acknowledge Active Command (a) This command is used to ensure that a device is responding to a data recorder or another SDI-12 device. = = Device address Command terminator The response: a<cr><lf> where a <cr><lf> Example: 0!0<cr><lf> = = Device address Response terminator 60 ___________________________________________________________________M210736EN-B Chapter 7 __________________________________________________ Getting the Data Messages Change Address Command (aAb) This command changes the device address. After the command has been issued and responded to, the sensor is not required to respond to another command for one second time in order to ensure writing the new address to the non-volatile memory. = = = = Device address Change address command Address to change to Command terminator The response: b<cr><lf> where b <cr><lf> = = Device address = the new address (or the original address, if the device is unable to change it) Response terminator Example (changing address from 0 to 3): 0A3!3<cr><lf> Send Identification Command (aI) This command is used to query the device for the SDI-12 compatibility level, model number, and firmware version and serial number. Command format: aI! VAISALA _______________________________________________________________________ 61 User's Guide ______________________________________________________________________ where a I != = = Device address Send identification command Command terminator The response: a13ccccccccmmmmmmvvvxxxxxxxx<cr><lf> where a 13 = = Device address The SDI-12 version number, indicating SDI-12 version compatibility; for example, version 1. 3 is encoded as 13 8-character vendor identification Vaisala_ 6 characters specifying the sensor model number 3 characters specifying the firmware version 8-character serial number Response terminator cccccccc vvv xxxxxxxx <cr><lf> Example: = = = = mmmmmm = 0I!013VAISALA_WMT50103Y2630000<cr><lf> Start Measurement Command (aM) This command asks the device to make a measurement. The measured data are not sent automatically and should be requested with a separate Send data command aD. The host device is not allowed to send any commands to other devices on the bus until the measurement is completed. When several devices are connected to the same bus and simultaneous measurements from the different devices are needed, Start concurrent measurement aC or Start concurrent measurement with CRC aCC should be used, see the next sections. See Examples of aM, aC and aD Commands on page 67. 62 ___________________________________________________________________M210736EN-B Chapter 7 __________________________________________________ Getting the Data Messages Command format: aMx!where a M x = = = Device address Start measurement command The desired sensor to make the measurement 1 = Wind 5 = Supervisor If x is left out, the query refers to the combined data message used for requesting data from several sensors with just one command. Command terminator ! = The response is sent in two parts: The response part one: atttn<cr><lf> The response part two (indicates that the data is ready to be requested): a<cr><lf> where a ttt n <cr><lf> = = = = Device address The measurement completing time in seconds The number of the measured parameters available (maximum number is 9) Response terminator NOTE For changing the message parameters, units and other settings, see Chapter 8, Sensor and Data Message Settings, on page 81. NOTE When the measurement takes less than one second, the response part two is not sent. VAISALA _______________________________________________________________________ 63 User's Guide ______________________________________________________________________ NOTE The maximum number of parameters that can be measured with aM and aMC commands is nine (9). If more parameters are to be measured, Start concurrent measurement commands aC and aCC should be used (for which the maximum number of parameters to be measured is 20), see the following sections. Start Measurement Command with CRC (aMC) Command format: aMCx!This command has the same function as the aM but a three-character CRC is added to the response data strings before <cr><lf>. In order to request the measured data, Send data command aD should be used, see the following sections. Start Concurrent Measurement (aC) This command is used when there are several devices on the same bus and simultaneous measurements are needed from the devices, or if more than nine (9) measurement parameters are requested from a single device. The measured data is not sent automatically and it should be requested with separate Send data command aD. where a C x = = = Device address Start concurrent measurement command The desired measurement 1 = Wind 5 = Supervisor If x is left out, the query refers to combined data message in which the user can request data from several sensors with just one command. See the examples below. 64 ___________________________________________________________________M210736EN-B Chapter 7 __________________________________________________ Getting the Data Messages ! = Command terminator The response: atttnn<cr><lf> where a ttt nn <cr><lf> = = = = Device address The measurement completing time in seconds The number of the measured parameters available (maximum number is 20) Response terminator NOTE For changing the message parameters, units and other settings, see Chapter 8, Sensor and Data Message Settings, on page 81. Start Concurrent Measurement with CRC (aCC) Command format: aCCx!This command has the same function as aC but a three-character CRC is added to the response data strings before <cr><lf>. In order to request the measured data, Send data command aD should be used, see the following sections. Send Data Command (aD) This command is used to request the measured data from the device. [. . . ] The only exception to this is the time between the stop bit of one character and the start bit of the next character. 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. 114 __________________________________________________________________M210736EN-B Appendix B __________________________________________________________ SDI-12 Protocol - When receiving a break, a sensor must detect 8. 33 milliseconds of marking on the data line before it looks for an address. [. . . ]