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Wednesday, July 18, 2018
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Modbus TCP over WiFi
Wireless connection of modes slave to industrial router and SCADA system.

Hi all,

We have just received a new gas monitoring device (Modbus TCP slave) in my work. I would like to connect it to to our SCADA system, based on Siemens S7-1500 controller. We already have exactly the same device installed in the process which is connected to the building network, and data are transferred to the Siemens controller through eWon Flexy (industrial router). This works absolutely fine. The only difference between these two sensors is that the new one will be portable, and operators will take it with them as they work in the process area. As the sensor is battery powered and there is not sufficient amount of Ethernet socket, I would like to make the connection to the building network and thus to the eWon router wirelessly. The maximum distance of the wireless connection would be up to 10 meters (the worst case). The eWon router provides Ethernet ports but not WiFi functionalities. Could I use a WiFi transmitter connected to the gas sensor and a WiFi receiver connected to the building network/the industrial router to create the connection? Can I use a WiFi router - 802.11 b/g/n? Do I need to somehow convert data before wireless transfer?

Thank you very much!!


You can ideally use a standard industrial wi-fi router to connect you Modbus TCP device. The router itself is just a bridge transparent to connect your field device to your control system; then it is not a big issue.

The critical point is how you will deploy it, I mean, if you are moving the devices across the plant to avoid to lose the wireless communication, I recommend to get a mesh network and then to map out where the device should work and then avoid to lose the communication.

Below you get some website with more information about wireless communication. (website in portuguese)


Yes, you can connect the gas sensor to a wifi receiver if it supports TCP/IP connections with an Ethernet port, and you can connect that wifi to another wifi. You should be able to use a 802.11 b/g/n as far as I know. Make sure to check for safety compliance.

You could also get portable cellular modem with a static IP. That would allow you to connect to the network (firewalls, etc. permitting), as long as you have a cellular signal for your setup. Make sure to check for safety compliance on that device too.

I specialize in SCADA. Maybe that will help you.