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March 2016

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From:
Robert Kondner <[log in to unmask]>
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Date:
Tue, 8 Mar 2016 11:48:24 -0500
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Bhanu,

 

  You gotta read a book on this. See: http://www.pyromation.com/Downloads/Doc/Training_TC_Theory.pdf

 

 

Myth: There should never be a third metal in the hot junction 

 

To create a thermocouple junction, all that is needed is to electrically short the ends together. Butting the wire ends against a metal surface will create a junction. Remember, that the thermocouple signal is generated over the entire length of wire.

 

  Lets say you have two side of the thermocouple, side A and side B and another material C.

 

The welding of side A to a material C results in a thermocouple being formed, The welding of side B to the material forms another thermocouple. The final sum of the two thermocouples equals the junction potential of A welded to B.

 

Tell me if I am wrong! Been known to happen!

 

Bob K.

 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Bhanu Sood
Sent: Tuesday, March 08, 2016 10:59 AM
To: [log in to unmask]
Subject: Re: [TN] Soldering a K Type TCouple to FR4 Board

 

If you weld each side to a third material, its no longer a junction, no thermo-"couple"..

 

On Tue, Mar 8, 2016 at 10:54 AM, Robert Kondner < <mailto:[log in to unmask]> [log in to unmask]> wrote:

> Hi,

> 

>  I do not think this is correct.

> 

>  My recollection of the physics is you can cut the bead off the thermocouple, weld each side to a 3rd material, and get the temperature of the material.

> 

> What this does is introduce additional junctions but the final output is always equal to the characteristics of the original bead. Even if you manage to diffuse other materials into the thermocouple wire materials it is the same case.

> 

> Anyone else out there have any thoughts?

> 

> Bob K.

> 

> -----Original Message-----

> From: TechNet [ <mailto:[log in to unmask]> mailto:[log in to unmask]] On Behalf Of Bhanu Sood

> Sent: Tuesday, March 08, 2016 8:43 AM

> To:  <mailto:[log in to unmask]> [log in to unmask]

> Subject: Re: [TN] Soldering a K Type TCouple to FR4 Board

> 

> Are you sticking the thermocouple head in SAC solder? Be careful!

> 

> Once you stick the t/c in SAC solder and melt to 250C (which bwt is 

> above the 185C curie point) the chromel which contains 90-percent 

> nickel and 10-percent chromium and alumel which contains approximately

> 95 percent nickel, with aluminum, silicon, and manganese making up the other 5 percent will alloy with the tin, changing the temperature e.m.f relationship. You may not have a working thermocouple afterwards.

> 

> 

> On Tue, Mar 8, 2016 at 8:14 AM, Bob Wettermann < <mailto:[log in to unmask]> [log in to unmask]> wrote:

>> Morning All:

>> 

>> Has anyone had success in soldering Type K Thermocouples to a PCB. 

>> The assembly call for a SAC305 no clean alloy....

>> 

>> There are 2 THole connections that will need to be hand-soldered as 

>> part of this assembly.

>> 

>> Thanks!

>> 

>> 

>> _____________________________________________________________________

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>> --

>> Bob Wettermann

>> BEST Inc

>>  <mailto:[log in to unmask]> [log in to unmask]

>> Cell: 847-767-5745

> 

> 

> 

> --

> Bhanu Sood

> Tel: (202) 468-8449

> 

> ______________________________________________________________________

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> 

 

 

 

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Bhanu Sood

Tel: (202) 468-8449

 

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