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Application note

Vaisala WXT520 and Nokeval 7470 V3.0Juha Hämäläinen / Nokeval Oy 21.6.2012


Nokeval 7470 analog output unit can be programmed to interpret messages from Vaisala WMT and WXT weather sensors. This requires configuring both of the devices. This application note will give instructions for this process. The supported Vaisala transmitters are WXT520, WXT510, WMT52, and WMT50. The WMT52 and WMT50 are similar to WXT520 and WXT510 but have less functions. This note applies to 7470 firmware versions V3.0 and up. For older 7470 versions, an older application note should be used.

Equipment needed

For Vaisala The weather station may be connected to the computer for configuration via a Vaisala service cable or using regular RS232 or RS-485 connection. The Vaisala unit may be configured with either Vaisala configuration software or alternatively with any terminal software, like HyperTerminal or TeraTerm. For 7470 The 7470 is connected to the computer for configuration using a programming cable. Two types are available: POLRS232 for RS-232 port, and DCS772 for USB port. The programming connector in 7470 is called POL. If no programming cable is available, the 7470 can be configured using RS-232 or RS-485 connection, but it will make things much more difficult. The jumper JP1 must be closed inside 7470 during configuration. The configuration software used is Mekuwin, available free from Nokeval web site.

How to go

Since the configuration flow depends on equipment available, please follow the flow chart on the next page. Each rhomb represents a decision, and each box states a procedure to do. The procedures have a section of their own in this application note. It is no use to read the whole document. "POL cable" in the chart means Nokeval programming cable, either POL-RS232 or DCS772.

Table of contents

Configuring Vaisala with Vaisala Configuration Tool.............................................................4 Configuring Vaisala with a terminal software.........................................................................7 Configuring Vaisala with Sicala.............................................................................................9 Connecting 7470 for RS-232/485 configuration..................................................................10 Configuring the 7470............................................................................................................11 Wiring...................................................................................................................................13



Vaisala service cable available Yes



POL cable available


Want to use Sicala


Configure Vaisala w ith terminal softw are

Configure Vaisala w ith Sicala

Configure Vaisala w ith Vaisala Configuration Tool


POL cable available


Connect 7470 for RS-232/485 configuration

Connect 7470 w ith POL cable

Configure 7470




Launch the Vaisala configuration tool. Select File/Connection Setup. Select your serial port. If you use the service cable, the baud rate is always 19200. Otherwise the baud rate is whatever is configured in the weather station; factory default is 19200. 8 bits, none parity, 1 stop. After closing the Connection setup window, the main window should say Connected in the status bar. If not, check the connections and that the weather station is powered up.

Use a profile

A profile that suits most applications can be downloaded from Nokeval web site to reduce or avoid the manual configuration work. Go to the 7470 product page, and save the Vaisala WXT520 recommended profile for 7470 in a file. In the Vaisala configuration tool, open File/Profile manager, and read in the file. Write to Device.

Manual configuration

Device settings Enable the Composite message auto transmission. The interval is recommended to be kept at 1 s. Select the ASCII protocol. Disable the other auto transmissions by enabling Polling only. The Port type is selected according to the cabling. The baud rate here must match what will be configured in the 7470; 19200 is a good choice. Data bits must be 8, Parity None, and Stop 1. Message settings

Select the parameters required. The Composite message section is the only that matters. Do not select more than 11 parameters, or the composite message may become too long. The items selected in the example picture are the recommended choices. Profile manager Vaisala Configuration Tool has a profile manager that allows viewing all the settings at once and saving them to a file. The profile manager can be used to check that everything is configured correctly. To read the current configuration into the Profile manager, click Read from Device button. Pay attention on the items marked

Sensors setup Most of the settings here are obvious. Refer to the Vaisala documentation for more info.

with a red asterisk (*).


Setting up the terminal software Open HyperTerminal (or any other terminal software) and create a session to the desired serial port. Use the baud rate that the weather transmitter uses (default 19200-8N1, service port always 19200). More detailed instructions for HyperTerminal: Launch the application. Create a new connection and name it as Vaisala, for example. Save your setup (File/Save) for future use. Next time you can skip these settings and simply open the saved setup. If the bottom of HyperTerminal says "Disconnected", select Call/Call. Testing the communications If the Vaisala is configured for automatic transmission, it sends messages like 0R1,Dn=000D... If you get mess, try other baud rates. If nothing, write command 0R1<enter> and see if Vaisala responds. If not, check the cabling and the supply voltage. Sending commands with Copy ­ Paste The commands described here may be copied to the clipboard and sent to the weather transmitter instead of manually typing them. Activate the text selection tool in your pdf reader. Go to the beginning of the command, keep the left mouse button pressed and move the cursor one row lower. Release the button. Select Copy. (This way we can copy the newline character too). Now go to the terminal software and select Edit/Paste to Host. The command is sent to the weather station. Stopping the automatic transmission If the Vaisala is sending automatic messages, it makes it difficult to configure. So those auto transmissions are recommended to be switched off while configuring. To do that, send the command below. It is recommended to be sent using the clipboard method as described above. 0XU,M=P,I=0 Changing Vaisala baud rate If you want to change the WXT/WMT baud rate, write for example 0XU,B=19200

Select a connection to your serial port where the weather transmitter is connected in.

Select File/Properties, Settings, Ascii setup. Select the correct baud rate.

And switch the station off for 30 s. Change the HyperTerminal to the new baud rate (Call/Disconnect, File/Properties/Configure and Call/Call again). Configuring the composite message The composite message is configured to contain the desired fields only. Which wind fields are included in the composite message, are configured with command like: 0WU,R=&01001100,U=M The 0's and 1's disable and enable fields. The first 0 or 1 defines if Dn (Wind direction minimum) is to be sent, the next defines Dm (Wind direction average) etc. 0=not included and 1=included. The "bits" have the meanings: Bit Field 1 Dn Wind direction minimum 2 Dm Wind direction average 3 Dx Wind direction maximum 4 Sn Speed minimum 5 Sm Speed average 6 Sx Speed maximum 7 spare 8 spare U=M defines that metric units are used (m/s). This application note will not repeat every detail about these settings ­ refer to the Vaisala manual. The pressure, temperature and humidity fields are configured with similarly: 0TU,R=&11010000,P=H,T=C Bit 1 2 3 4 5 6 7 Field Pa Air pressure Ta Air temperature Tp Internal temperature Ua Air humidity spare spare spare

Bit Field 8 spare P=H selects pressure in Hectopascals. T=C selects temperature in Celsius. The rain fields are configured this way: 0RU,R=&00100100,U=M,S=M Bit Field 1 Rc Rain amount 2 Rd Rain duration 3 Ri Rain intensity 4 Hc Hail amount 5 Hd Hail duration 6 Hi Hail intensity 7 spare 8 spare Finally any supervisor fields are switched off: 0SU,R=&00000000 Now, test that the composite message contains the correct fields: Send command 0R0 Vaisala should respond something like this:


Numbering the parameters Number the order of the parameters:

0R0,Dm=091D,Sm=0.1M,Ta=21.6C,Ua=9.9P,Pa=1025... 1...2.......3.......4........5.......6.....

This is necessary later when configuring the 7470. Finally enable the automatic transmission Send command 0XU,I=1 Now the weather station should send only one type of message beginning with 0R0. Vaisala is done. Close or disconnect the HyperTerminal.


The 7470 allows sending commands to the RS-232/485 bus from the POL (programming) port. Nokeval has planned to make a PC software later that would configure both the 7470 and Vaisala unit. While this software is not available, the commands can be sent using a software called Sicala. This is not convenient but may still be useful in some situations. Sicala is a testing software for devices using Nokeval SCL protocol. The 7470 uses this protocol on its POL port. Set-up Download Sicala from Nokeval website and install it, or install it from Nokeval Software CD. Connect the programming cable between your PC and 7470. Close MekuWin totally before launching Sicala, to free the serial port. Wire the 7470 and Vaisala weather station together, if they are not already. Look at chapter Wiring. In Sicala, select the COM port of the programming cable. Select 9600 baud, 8N1 bits, SCL with BCC protocol, address 0. Write command TYPE ? And press enter. If all is OK, you should see a green response "7470 V3.0". Sending commands for Vaisala The command C is used to request the 7470 to send a command to Vaisala. In the Command box, write C, one space, and a Vaisala command, and press enter (or click the Send button). An example: To hear what Vaisala has to say, use command G (get). In Sicala command box, write G only, and press enter. You should see a Vaisala message in the Response box. Since the messages are buffered in the 7470, press enter several times to read out all messages, until an empty response is returned (green <> in the Response box). The message buffer in 7470 is limited in size, about 400 bytes, so the oldest messages will be discarded if too much data is input before reading it out. Configuring Proceed as in chapter Configuring Vaisala with a terminal software, 7, but send the commands with C command and read the responses with G command. C 0R1 This sends command 0R1 (request wind data) to RS-232/485 port. Getting responses


Using RS-232 or RS-485 for configuring the 7470 is necessary only if a programming cable is not available.


RS-232 Disconnect the Vaisala unit from the 7470. Wire the Tx of 7470 to Rx of your PC, and vice versa. Also connect the common. For a D9 RS-232 connector, the wiring goes: 7470 4 5 6 Name Rx Common Tx PC 3 5 2 RS-485 Connect the terminal 1 (D1) of the 7470 to the D1 or + terminal of your RS-485 port. Connect the terminal 2 (D0) to the D0 or ­ terminal of your RS-485 port. Also connect the commons together, if possible.


The RS-232/485 port of the 7470 can be configured for various protocols, but SCL and Modbus RTU protocols allow configuration with MekuWin software. To ensure that the 7470 is using the SCL protocol, 9600 baud, and address 0, close the jumper JP1 inside the enclosure. The 7470 manual will give details on this. When the configuration is done, remove the jumper.


Launch MekuWin. Select the appropriate COM port, SCL protocol, 9600 baud, and address 0 or 126. Try to connect.



Open a MekuWin connection to 7470, using the serial port of the programming cable, SCL protocol, 9600 baud, address 0 (if using RS-232/485 for configuration see the page 10). Connect using the Master button.

Serial setup

Go to the Ser submenu. Set up:

· · · ·

Mode = Ascii Baud = 19200 (or same as Vaisala) Parser = Classic Stime = 10

Channel setup

Each of the four analog outputs are configured individually in the corresponding submenus Ch 1 to Ch 4. Defining the field The From setting defines which parameter is picked from the composite message coming from the weather station. "0R0" is interpreted as parameter 1 and it contains no useful information. Setting From=2 will instruct 7470 that this output follows the second field in the message, Dm=105D in most cases, giving the wind direction. If you haven't seen what the message looks like, use the Monitor function of MekuWin and look at RecvString. If the WXT520 has been configured according to the examples in the Vaisala chapter, page 5, then the fields will be: Field Description 1 2 3 4 5 6 7 8 9 0R0, can be neglected Dm Wind direction average Sm Speed average Sx Speed maximum Ta Air temperature Ua Air humidity Pa Air pressure Ri Rain intensity Hi Hail intensity

This applies to the WMT52 too, but only fields 1 to 4 will be available. Scaling the analog signal Range defines the analog output signal type. Lo and Hi define the parameter values that will give the low end and high end signals. For example, to get 4 mA when the wind speed is 0, and 20 mA

when it is 50, set Range=4-20mA, Lo=0, and Hi=50. The 7470 does not know the

measurement unit ­ it is defined in the Vaisala configuration. Finally click the Save to EEPROM button.


Every RS-485 bus should have one or two devices capable to feed a weak current on the bus. The purpose of the current is to have a small (0.2 to 5 V) voltage between the data wires when nobody is transmitting on the bus. This is called failsafe, polarization, or biasing. If there is no polarization, the devices may receive phantom data from the bus when it is idling. Vaisala WXT520 is not able to provide the polarization. The current 7470 model (PCB version 1.2 or newer, used since May 2012) is able to provide the polarization current. Set the jumper JP4 to position "Polarized" or "Terminated and polarized" per 7470 manual. The older 7470's (PCB V1.0-1-1) do not have a dedicated polarization jumper, but similar effect can be achieved by selecting a 2-wire position with jumper JP4.


Remove the service cable from the weather station, if still attached, to enable the auto-transmission. Wire the Vaisala and 7470 together, if not already. If using a programming cable, open the Monitor on MekuWin. Readings should appear in Ch2 and other items. Analog outputs should activate.

Several 7470's

Several 7470's can be parallel-connected in an RS-485 bus and configured to pick different parts of the Vaisala composite message.


7470 outputs are 0 mA or 0V Remove the programming cable, if still attached. 7470 is not receiving proper messages. Make sure that the weather station is auto-transmitting, and that the baud rates match. Also check the serial bus wiring. Remove the service cable, if attached. Check the configuration once more.

Vaisala not autotransmitting

Also look at the troubleshooting instructions in the 7470 manual.



Separate serial and power wiring

1 2 3 4 5 6 19 20 Twisted pair 1 2 3 4 5 6 11 12



+ -


Combined wiring

1 2 3 4 5 6 19 20 Twisted pair 1 2 3 4 5 6 11 12



+ -


Since Vaisala does not have isolation between serial and power ports, one wire can serve as a serial common and power supply minus wire. If there are several 7470's, just connect them in parallel.

Wiring with Vaisala M12 cable

Grey Blue 1 2 3 4 M12 5 6 Clear Brown 11 12



+ -



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