exida just completed certification of a new sensor product that uses wireless communication to signal a safety logic solver of a potential problem. Shortly after the certificate was posted, a challenge arose: “How can wireless be used for safety?” Well, it is different. A designer must be fully aware of the different time response issues. The system must be configured to fail-safely upon loss of the wireless signal. The system timeout must be long enough to deal with the redundancy of radio media. But it is safe. The protocols have been through careful analysis and will provide a safe message when the signal is good.
“But what about security? I do not want some hacker to be stand near our fence and trip the plant.” Well, I do not doubt the ingenuity of the determined hacker. But it would be hard to stand outside a plant fence and initiate a trip. The spread spectrum signals combined with encryption will stop the amateurs and most of the professionals. Of course that applies to all wireless, not just functional safety.
There are nice advantages to the use of wireless in functional safety if the response parameters meet the application. It is great to see certified wireless functional safety products hit the market.