Galvanic Isolating Barrier for RS485

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Thread Starter

Carl Burgess

Does anyone know of a manufacturer that makes an intrinsic safety isolating barrier for 2 Wire RS485 or even RS422 ?. Regards, Carl
 
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Jonathan A. Brown

We have recently been researching this, fairly heavily. None of the major Isolator/Barrier vendors make an RS485 isolator for IS. They all make RS232. The reason is because there is generally no need for one. An RS485 circuit qualifies as a non-incendive circuit for class 1, Division 2 areas under the NEC Section 500, thus, under "normal operating conditions", the circuit is incapable of causing an arc or spark. If you are planning on a Division 1 installation, I'm not sure, but we are still looking into it ourselves. We intend to install the circuit using standard (not IS rated) optical isolation. I know that Telebyte and B&B Electronics both sell them. I suspect Black Box does also. Jonathan > Does anyone know of a manufacturer that makes an intrinsic safety isolating barrier for 2 Wire RS485 or even RS422 ?. > > Regards, > Carl >
 
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Carl Burgess

This looks like the device I've been looking for. I had already looked at the Stahl website, but not found it ! Thanks, ~Carl
 
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Carl Burgess

> Most probably the product is available from MTL. Nope, definitely not. MTL do suitable zener barriers, but their galvanic stuff is only designed to work with their operator interfaces - it doesn't support proper RS485. I'd already spoken extensively to MTL before posting the query ! ~Carl
 
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