Wireless Technology in Instrumentation

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Do you know what is convenient?

Role?

Wireless technology is just another way to transmit data from the instrument to the PLC or DCS. Instead of sending the data through wires (either current, voltage, or digital methods), the data is sent through the air via radio waves. It eliminates the bundles of wires that are scattered around the plant area.

To address power requirements of the instruments, a single wire can be layed out that goes to each instrument in turn so, in effect, only one wire goes around the plant area. An alternative is to put batteries on the instruments. The instrument will inform you (hopefully a month or at least a week before it dies) that the battery needs changing.

What if it's a really big factory? Does a small instrument have enough power to transmit over long distances?

Another version of the wireless technology says that repeaters can be installed at strategic points around the factory. When an instrument transmits, the repeater rebroadcasts it (sort of like a cellular phone network) and the receiver at the main panel gets the data.

These have been used in the Alaska Pipiline since I can remember (ca. 1987).

Applied mainly in difficult to reach areas and where cabling is nearly impossible.

Wireless is of a great value: no cables anymore that can be faulty, broken, wrong installed.

No connections have to be made for temporarily interventions, this is especially handy in Ex classified zones.

Of coarse you need to feed the sensor, but with the EnOcean technology this is even not needed. (sunlight, temperature difference and vibrations are used to convert these energy forms into the tiny bit of energy that the transmitter needs to send out it's data.

Wireless you can do the measurement where you want: no limit on cable distance and/or trajectory.

We are working on a temperature controller for tracing that has a Bluetooth interface to communicate with it's programmer. This way the maintenance person does not have to ope the unit to connect it's cable, as the unit is fed by 230 (up to 270VAC) opening a device while powered is a hazard, only done is special occasions. (we only need it when we want to set the limiter, which is in fact only done once while commissioning the unit.)

The maintenance guy can walk under the pipe rack, and check the controller which is above him. Without having to connect to the unit.

For now we limit this wireless to the programming, but our plan is to replace the complete field bus with a wireless system where the controllers are the nodes of a network. The reason for doing this in a later stadium is that we want to hit the market as soon as possible now.

Recently I did a project with the EnOcean technology and it enabled me to have the temperature of each room centralised available without pulling wires or having to replace batteries.

If you have the possibility, play with it and you will find the power of wireless.

We have been experiementing with it in regard to machinery vibration sensing. Work well. I think in applications where pulling wire is expensive, wireless is a sensible alternative.