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19/06/2013
KTA-282 Modbus TCP Weather Station Gateway

Keen to make use of Ethernet’s rising popularity in industry, we have recently released the KTA-282 Modbus TCP Weather Station Gateway. This unit is essentially an upgraded version of our GWY-141 Vantage Pro 2 Modbus RTU Interface, adding Ethernet functionality and a raft of additional features.

The KTA-282 allows any one of our weather stations to be connected to a controller (PLC, RTU, SCADA, etc) via the Modbus RTU (on RS-485) or Modbus TCP/IP (on Ethernet) protocols. Monitoring and control actions can then be carried out on the weather data.

A Weather System

The KTA-282 is best explained through a hypothetical case study:

A solar farm has been commissioned in outback Australia by madeupcorporation PTY LTD. The operator requires weather monitoring both onsite, and at the company’s headquarters in Melbourne (some 3000 km away).

It is feasible to operate the farm if solar radiation is above 800 W/m2. It is dangerous to operate the reflectors above 50kmh winds from the east/west, and 70 kmh from north/south.

They purchase the Vantage Pro 2 Plus weather station kit, the weatherlink cable, and the KTA-282.


The ISS Plus (the sensors) are mounted outside next to the solar reflectors. These sensors then send their signal 300 metres wirelessly to the console - housed inside their control room. The console is connected to the KTA-282 via the weatherlink cable. The KTA-282 is connected to the control station’s LAN via an Ethernet cable. Housed in the adjacent room is a PLC also connected to the LAN.

They begin by configuring the KTA-282. On first startup, the onboard DIP switches are used to set the IP address to 192.168.1.100; the same subnet as their LAN. This IP address conflicts with their network printer (currently powered down) so they decide to change it to 192.168.1.200 using a webbrowser on their office PC.


The webpage also shows them that the currently selected units are farenheit (temperature), inches of mercury (pressure), miles per hour (wind speed), and inches (rain). They change these to celsius, hectopascals, kilometres per hour, and mm using ModbusViewTCP(could use any Modbus master).

Onsite Set-up

The controller polls the KTA-282 for weather data over Modbus TCP/IP. If the sensed solar radiation is above 800 w/m2, the solar farm is activated.

The system will be disabled if the 10min wind gust exceeds 50 kmh from direction 45&#176 through 135&#176 and 225&#176 through 315° and all other directions if exceeding 70 kmh. When disabled, the reflectors home parallel to the ground, minimising their sale area so they don’t snap off in the high wind.

Offsite Setup

The onsite LAN router is configured to port forward packets from the KTA-282 onto the Internet. Back at the Melbourne office, they use ISeeModbusTCP to poll the KTA-282 (can be polled by up to three Modbus masters simultaneously) and generate graphs of solar radiation, windspeed, wind direction, and any other weather data that takes their fancy. All data is logged to a spreadsheet for archiving.


Graphs of wind speed and direction generated by IseeModbusTCP

Remote Configure

One morning, in summer, an employee notices that the logged sunrise and sunset times are a full hour off what they should be. The weather station has not been configured for daylight savings. From their Melbourne office, they use the KTA-282 PC Application (available as a free download) to change the internal configuration of the weather station – without requiring an onsite visit.


Custom Applications

Some months later, they are approached by a client requiring weather data from the solar farm. The client would like a graphical program that shows wind speed and direction on a virtual wind vane. Madeupcorporation’s software engineer writes up a program to the client’s specifications, using the XML request function to easily get the required information out of the KTA-282. This data is returned in a standardised XML format over HTTP; requiring minimal effort to request and decode.

Field Updatable

Three years later, madeupcorporation decide to update their KTA-282 to the latest firmware release. They download the encoded firmware file from this website, and upload it to the KTA-282 via a web browser for free.

Weather Station Kits

If madeupcorporation were wise, they would have bought their weather station in the cheaper Modbus kit. Kits are also available for the weather stations without Modbus. In a future news article we will provide an in-depth explanation of our weather kits and accessories.

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-BS





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