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TC wire and dsub

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jan_de_jong(at)casema.nl
Guest

Posted: Thu Aug 15, 2019 5:38 am Post subject: TC wire and dsub

Theoretically, extending thermocouple wires using a dsub connector 

(with, say, gold over bronze contacts) should be ok provided any 

temperature gradient across the connector is ignored. The thermocouple 

voltages across the connector cancel out to 0.



In practice there could be a problem with corrosion of a thermocouple 

wire where it meets gold.



Is there experience?



Thanks,

Jan de Jong

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nuckolls.bob(at)aeroelect
Guest

Posted: Thu Aug 15, 2019 6:28 pm Post subject: TC wire and dsub

At 08:36 AM 8/15/2019, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: Jan de Jong <jan_de_jong(at)casema.nl>



 Theoretically, extending thermocouple wires using a dsub connector (with, say, gold over bronze contacts) should be ok provided any temperature gradient across the connector is ignored. The thermocouple voltages across the connector cancel out to 0.



 In practice there could be a problem with corrosion of a thermocouple wire where it meets gold. 	


  Gold is electrolytically inert. I think

  most thermocouple alloys are similarly

  resistant to oxidation.  I've run

  TC wires though d-subs for decades with

  good success . . . with one caveat:

  

  My tasks were temporary instrumentation

  installations so I've not personally

  observed/demonstrated longevity in

  field service. But given the low

  reactivity of the alloys involved,

  I'm pretty confident that they'll

  last a long time.



 

 

   Bob . . .

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nuckolls.bob(at)aeroelect
Guest

Posted: Fri Aug 16, 2019 6:15 am Post subject: TC wire and dsub

At 08:36 AM 8/15/2019, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: Jan de Jong <jan_de_jong(at)casema.nl>



 Theoretically, extending thermocouple wires using a dsub connector (with, say, gold over bronze contacts) should be ok provided any temperature gradient across the connector is ignored. The thermocouple voltages across the connector cancel out to 0.



 In practice there could be a problem with corrosion of a thermocouple wire where it meets gold. 	


  Gold is electrolytically inert. I think

  most thermocouple alloys are similarly

  resistant to oxidation.  I've run

  TC wires though d-subs for decades with

  good success . . . with one caveat:

  

  My tasks were temporary instrumentation

  installations so I've not personally

  observed/demonstrated longevity in

  field service. But given the low

  reactivity of the alloys involved,

  I'm pretty confident that they'll

  last a long time.



 

 

   Bob . . .

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racerjerry

Joined: 15 Dec 2009
Posts: 202
Location: Deer Park, NY

Posted: Sun Aug 18, 2019 3:55 am Post subject: Re: TC wire and dsub

I might be more concerned when using Type J (Iron / Constantan) thermocouples.  You sure would want to make every effort to keep any moisture out and away from the iron.



Jerry King

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_________________
Jerry King

jan_de_jong(at)casema.nl
Guest

Posted: Sun Aug 18, 2019 6:09 am Post subject: TC wire and dsub

Thanks,

     Jan de Jong

     

     On 16-8-2019 04:25, Robert L. Nuckolls,       III wrote:

     

      	  Quote: 	
		                At 08:36 AM 8/15/2019, you wrote:

               	  Quote: 	
		  -->           AeroElectric-List message           posted by: Jan de Jong <jan_de_jong(at)casema.nl> (jan_de_jong(at)casema.nl)

           

           Theoretically, extending thermocouple wires using a dsub           connector (with,           say, gold over bronze contacts) should be ok provided any           temperature           gradient across the connector is ignored. The thermocouple           voltages           across the connector cancel out to 0.

           

           In practice there could be a problem with corrosion of a           thermocouple           wire where it meets gold. 	
       

        Gold is electrolytically inert. I think

        most thermocouple alloys are similarly

        resistant to oxidation.  I've run

        TC wires though d-subs for decades with

        good success . . . with one caveat:

        

        My tasks were temporary instrumentation

        installations so I've not personally

        observed/demonstrated longevity in

        field service. But given the low

        reactivity of the alloys involved,

        I'm pretty confident that they'll

        last a long time.

       

       

                

             Bob . . .

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