Emerson Exchange 365

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M-Series RTD Card channel interference

We had an issue last night with an 8-channel RTD card, where tightening a loose wire on an RTD (ch.8) caused the temperature indications to fluctuate drastically on channels 5, 6, and 7.  Very minor interference was seen on channels 1-4.  These are all 3-wire Pt.100 RTDs.  Our technician for the other side of the plant has seen similar behavior on an RTD card when one of the RTD wires get shorted while connected to the I/O card.  His solution was to install transmitters and wire into an analog input card.  Has anyone else seen this behavior?  Is there another solution to this issue?  We are short on space in the existing cabinet and I'm looking for other options. 

Thanks,

Kathy

Kathy Pate

Toray Carbon Fibers America

Decatur, AL 35601

kathy.pate@toraycma.com

• M-series
• RTD Card

kathrynpate

• 3 Jun 2019 5:21 PM
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6 Replies

• Darrell Cole

  

  • 1 Apr 2020 2:50 PM

  Was this issue ever resolved? We have also experienced this.
  
  Thanks,
  Darrell Cole
  
  Darrell.Cole@US.Indorama.net

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• Andre Dicaire

  

  • 1 Apr 2020 3:05 PM

  In reply to Darrell Cole:

  Your best bet to get to the bottom of this is to log a call with the GSC. Technical product issues are best handled through them, and it is their main role.
  
  I cannot be sure, as I don't have any documentation to support this, but it may be that the 8 channels are divided into 2 sets, 1 through 4 and 4 through 8. Each set shares some circuitry on the card and it is possible that electrical disturbance on one channel affects the other 4. Maybe a static discharge occurred as you touched the terminals. Simple to rule out by using a ground strap and performing the same type of work. If the issue occurs when properly grounded, I'd log a call and ask them to dig into and explain this. They will ask you for the Card and firmware revisions, and all the other info.

  Andre Dicaire

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• kathrynpate

  

  • 1 Apr 2020 4:37 PM

  In reply to Darrell Cole:

  Hi Darrell. Andre is correct. There are 2 A/D converters for the RTD Card so channels 1-4 are multiplexed through one and channels 5-8 are multiplexed through the other. It took a day or two, but GSC finally sent me some documentation on the issue. Last year I was told this applies to M-Series and S-Series RTD and TC cards. Our technicians know to use insulated tools when working on RTDs and this issue occurred when an operator used a non-insulated screwdriver to tighten the loose terminal. We reviewed all of the RTDs that have this issue and decided that there were only a few critical ones that we would add a transmitter too.
  
  Good luck:)
  Kathy

  Kathy Pate

  Toray Carbon Fibers America

  Decatur, AL 35601

  kathy.pate@toraycma.com

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• Darrell Cole

  

  • 1 Apr 2020 6:19 PM

  In reply to kathrynpate:

  Thank you both for the response. I believe we may also have to review our RTDs and decide which ones to add a transmitter to. Over the past two weeks we have had this happen twice.
  
  Thanks,
  Darrell

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• Curtis Byrd

  

  • 18 May 2021 7:49 PM

  In reply to kathrynpate:

  Hello Kathy:
  I realize that this post is somewhat dated. But, I am interested in knowing if you have any documentation supporting your explanation. Thanks!

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• kathrynpate

  

  • 18 May 2021 8:13 PM

  In reply to Curtis Byrd:

  Hi Curtis -

  These documents were sent to me from Emerson when I had the open call.  See page 10 of the .pdf for the discussion about the card having 2 shared "A/D" converters.  I see no copyright on these documents so I think they are ok to add here.  Hope this helps:)

  Fundamentals of Temperature Measurement using RTD and TC.pdfField Wiring recommendations.docx

  Kathy Pate

  Toray Carbon Fibers America

  Decatur, AL 35601

  kathy.pate@toraycma.com

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