Wireless Modbus TCP

Wireless Modbus

If you asked the average man or woman on the street about wireless communications, they would tell you it that it is an amazing feat of science to be able to send music, baseball games, and Uncle Al’s Ham Radio broadcasts through the air.

An Italian, Guglielmo Marconi from Bologna Italy, is often credited as the inventor of the radio, but the truth is many others had done successful experiments prior to Marconi. Much of what Marconi did was built on the work of Heinrich Hertz, who, as early as 1888, demonstrated that electromagnetic radiation could not only be generated but also detected. For a while, these waves that we now call radio were commonly called “Hertzian” waves. Hertz lost that distinction, but the measurement of cycles per second is credited to Heinrich Hertz and we call it a Hertz.

Today, sending signals through the air is still somewhat mysterious to most of us, but it shouldn’t be. Air is simply another conductor like copper wire. Signals are injected into the conductor and recognized at another place on the conductor. Air or any other material, it doesn’t matter that much. It works the same way no matter what the material.

Now, in manufacturing, sending signals through the air has always looked risky. Signals can be easily disrupted by fork trucks and other materials moving around the plant. Electromagnetic radiation from motors and other rotating equipment can interfere with wireless signals. It was generally more comfortable to see a cable and know that if we put EtherNet/IP, Modbus TCP, or PROFINET into one end, it was going to be available at the other end of the cable.

There were applications where plant people had to use wireless even though it was somewhat uncomfortable to many of them. Rotating machinery was always one of those use cases. Engineers had tried all sorts of wired communication systems that could cross the boundary from a stationary piece of equipment to a rotating piece of equipment – slip rings, for example – but none could match the reliability of a wireless system.

Wireless communications, especially wireless Modbus TCP, has now been in plants for a good fifteen years or more. Control engineers are now more comfortable with it and understand that a wireless Modbus TCP system functions exactly like a wired Modbus TCP system. Just like in the wired world, there is still a Modbus TCP client device to open connections and send Modbus messages to end-devices. The wireless end-devices, Modbus TCP server devices, connect the physical world to the ones and zeros of the virtual, Modbus TCP world, just like in a wired system.

The big advantage to wireless Modbus TCP and, of course, all wireless systems is no cabling. Not only don’t you have to purchase cable, but you also don’t have to pay for the labor to install the cable, and you don’t have terminations to make for the network. Today, with the cost of metal commodities soaring, connectors are a lot of the cost of new equipment.

Wireless is not cost-free though. Wireless Modbus TCP and other wireless equipment must have a wireless transmitter and receiver, and that transmitter/receiver must be certified by the federal government. And, of course, not all wireless is the same. In some applications like wastewater or tank farms, signals need to travel long distances. In other applications, like machine I/O, transmitters can be within a few feet of receivers. Some wireless systems are designed to penetrate walls, floors, and other kinds of obstructions. The application determines the frequency, and the frequency determines the kind of module required – and that is directly related to the cost.

RTA has a range of wireless solutions for moving your data around the factory floor. Give one of our applications engineers a call on 800-249-1612.

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