Nokeval WS425 wind sensor, 7470 analog output unit Application note

Application note

Vaisala WS425 and Nokeval 7470 V3.0

Juha Hämäläinen / Nokeval Oy 27.8.2008

General

Nokeval 7470 analog output unit can be programmed to interpret messages from

Vaisala WS425 wind sensor. Although the

WS425 has analog outputs of its own, this brings some advantages. The serial signal

(RS-485) can be transferred over a long distance without degradation. The 7470 provides standard 0-10V and 4-20mA signals. The moving average filter can be applied, which is not possible with

WS425's analog outputs.

To get the devices working together, both of the devices have to be configured. This application note will give instructions for this process.

This note applies to 7470 firmware versions V3.0 and up.

The WS425 has to be ordered for serial output (RS-232/422/485). It is not possible to use the SDI signal with the 7470.

This application note is to complement the

WS425 and 7470 manuals, not to replace them!

Selecting the serial bus

In this application, it is possible to use

RS-232, RS-422, and RS-485 buses.

RS-232

RS-232 is usable only, when the bus is moderately short. Exceeding 40 meters is not recommended.

RS-485

This is the best option in most cases. A 4wire cable can be used; one wire serving both as a power supply minus and

RS-485 common.

Equipment needed

For Vaisala

The WS425 has to be configured to use the NMEA Standard or the NMEA

Extended format. If this is the factory setting, and any of the other settings need no modification, then there is no need to configure the WS425.

The weather station may be connected to the computer for configuration using regular RS-232/422/485 connection.

The settings are accessed with any terminal software, like HyperTerminal or

TeraTerm.

RS-422

Since the wind sensor auto-transmits, and the 7470 never transmits, RS-422 is virtually the same as RS-485 in the final operation.

Selecting

In the WS425, the bus is selected with wire links at the connector pins 5...7. In the 7470, there is no need to adjust anything. See wiring diagrams at the end of this note.

For 7470

The 7470 is connected to the computer for configuration using a programming cable. Two types are available: POL-

RS232 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. The jumper JP1 must be closed inside 7470 during configuration.

The configuration software used is

Mekuwin, available free from Nokeval web site .

CONFIGURING THE WS425

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 wind sensor uses (default

9600-8N1 or 2400-8N1).

More detailed instructions for

HyperTerminal:

Launch the application. Create a new connection and name it as Vaisala, for example.

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, 8 bits,

None parity, 1 stop bit.

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.

Opening the configuration mode

Type Open<enter> as fast as possible. A menu should appear. Refer to the WS425 manual for details.

Correct settings for the 7470

Operation Mode must be NMEA Standard or NMEA Extended. The 7470 can not interpret the other messages.

Data bits should be 8 and Parity None, although 7 Even and 7 Odd will work also;

7470 will discard the parity bit.

The Output Interval must not be 0.

The other settings can be configured freely.

Closing the configuration mode

Select function 14. The wind sensor should now start transmitting the NMEA messages, beginning with $WIMWV or

$PAMWV.

CONNECTING 7470 FOR RS-232/485

CONFIGURATION

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

Wiring

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:

5

6

7470 Name

4 Rx

Common

Tx

5

2

PC

3

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.

Jumper

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

Configuring

Launch MekuWin. Select the appropriate

COM port, SCL protocol, 9600 baud, and address 0 or 126. Try to connect.

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.

CONFIGURING THE 7470

Connecting

Open a MekuWin connection to 7470, using the serial port of the programming cable, SCL protocol, 9600 baud, address

0. Connect using the Master button.

Serial setup

•

•

•

•

Go to the Ser submenu. Set up:

Mode = Ascii

Baud = same as WS425

Parser = Classic

Stime = 10

Channel setup

Each of the four analog outputs are configured individually in the corresponding submenus Ch 1 to Ch 4.

The From setting defines which parameter is picked from the NMEA message coming from the wind sensor. "$WIMWV" is interpreted as parameter 1 and it contains no useful information. Setting

From=2 will instruct the 7470 that this output follows the second field in the message, which is the wind direction.

From=4 means wind speed.

The structure of the NMEA message can be seen in the WS425 manual, and also in item RecvString of Monitor of MekuWin

(available only when using the programming cable and when the wind sensor is connected and transmitting).

It is advisable to set the From settings of the unused channels to 2 or 4, to prevent the safety timer from expiring on these channels, which would make the diagnostic LED inside the case to blink an error code.

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. 7470 does not know the measurement unit – it is defined in the

WS425 configuration.

Finally click the Save to EEPROM button.

Test

Wire the WS425 and the 7470 together, if not already.

The NMEA message should appear in the

RecvString of MekuWin Monitor, and all of the diagnostic lamps should be dark. If not, check that the devices are properly interconnected, and that the baud rates match. Refer to the troubleshooting instructions in the 7470 manual.

In the MekuWin monitor, the Ch2 should indicate the current wind direction, and

Ch4 the wind speed. The Out1 to Out4 should give the analog output signal in mA or V.

WIRING

RS-485/422

WS425

12

13

14

10

11

8

9

1

4

5

2

3

6

7

Twisted pair

11

12

1

4

5

2

3

6

7470

+

-

24V PSU

+

-

12V PSU

In case of RS-422, omit links in WS425 pins 10 and 14, and have separate wires for these. They are not connected in 7470 at all, but allow remote configuration.

RS-232

WS425

11

12

13

9

10

7

8

14

4

5

6

1

2

3

11

12

4

5

6

1

2

3

7470

+

-

24V PSU

+

-

12V PSU

The connection from the 7470 pin 6 to the WS425 pin 10 is optional. In normal operation it is not used, since the 7470 never transmits, but it may be useful for configuration purposes.