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Surge protection on thermocouple inputs

Surge protection on thermocouple inputs

Surge protection on thermocouple inputs

(OP)
Didn't find anything definitive in a search here, and I Googled the web, too.  

One of my minor stations took a pretty good lightning hit during a recent storm and blew a bunch of I/O cards, all RTD and thermocouple inputs.

Not really in my purview as a power guy, but is there a particular surge suppressor made to be inserted between the thermocouple wire going to the field and the I/O card for our control system.

I found several different surge suppressors for RTD's but I seem to be missing something that will work for the thermocouple circuits.  If you have specific models in mind, I'd prefer DIN rail mounting.

old field guy

RE: Surge protection on thermocouple inputs

Possibly remote transmitters and a 4:20 ma system.
Easy to change I/O cards.
You may be able to ground one lead of the thermo couples.
A close hit by lightning is hard to protect against.
 

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Surge protection on thermocouple inputs

(OP)
Bill--

You've mirrored my thoughts so far.  Management (and the instrumentation guys) doesn't want to go with remote transmitters because of the complexity of the changeover.

I just had a conversation with the boss bout protection against really close/vigorous hits.  I was hoping somebody knew of a DIN-mount device I could put in the control cabinet between the incoming TC lines and the I/O card.  Such things are common as mud for other I/O
 

old field guy

RE: Surge protection on thermocouple inputs

OFG --

I've had good luck with Ditek, they're mostly into commercial-grade stuff.  See what you can see at www.ditekcorp.com, or get in touch with their tech support guys.

With just a thermocouple (low impedance, small signal), you might be able to get some relief with just a bunch or 15V MOVs across the TC terminals and to ground?

Just my thoughts...

Let us know what you decide on!

Good on ya,

Goober Dave

 

RE: Surge protection on thermocouple inputs

Thermo couples are such low impedance that it must be common mode voltages blowing the I/Os.
Put whatever suppressors you can find on the system. The next time you get a close in hit, say:
"Wow. It's impossible to protect against a hit that close!"
And then replace the I/Os and the surge suppressors. grin
Seriously, Goober Dave may have the best answer.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Surge protection on thermocouple inputs

What about an intrinsic safety barrier.  Although this applies a barrier 'backwards', protecting the receiver from a fault in the field (as opposed to protecting the field device from arcing/sparking due to a fault in the safe/receiver area).  Why wouldn't it work?

Of course, an I/S barrier costs almost as much as a low end temp transmitter.  

 

RE: Surge protection on thermocouple inputs

A barrier would work very well.  Nice idea.  It doesn't require power either.

Keith Cress
kcress - http://www.flaminsystems.com

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