[volt-nuts] Thermal EMF - more results

[Neville Michie]

All this talk about thermal EMFs may not be particularly relevant.
Solder is used in connections between two metallic objects, like wire and 
a terminal. The thermal EMFs between a soldered copper wire and copper terminal
have exactly equal and opposite values between the solder and the metals.
I first met this in mid 60s making thermocouples, I was told that they should be welded 
not soldered because of the solder metal EMFs. I did both soldered and welded 
over the years, mainly for practical considerations, and although some situations 
were quite critical, I have never found evidence that solder matters. Even if you consider 
a metal like tin diffusing into the copper and changing its EMF, adjacent to the area 
of diffusion is a reverse gradient of tin concentration and thermodynamic considerations 
dictate that there is no effect for static conditions.
The worst effect is the response of the junction to a persistent thermal 
gradient, but this is hard to maintain over the distance of solder thickness.
cheers,
Neville Michie


> On 9 Jul 2016, at 8:56 am, Herbert Poetzl <herbert at 13thfloor.at> wrote:
> 
> On Wed, Jul 06, 2016 at 08:53:19PM +0200, Andrea Baldoni wrote:
>> On Wed, Jul 06, 2016 at 03:42:18PM +0200, Herbert Poetzl wrote:
> 
>>> Any plans on testing Sn42/Bi57.6/Ag0.4 ?
> 
>> Hello Herbert.
> 
> Hey Andrea,
> 
>> I don't have any source of it. My supplier (Heraeus) hasn't it,
>> at least, it wasn't included in the list of samples they are
>> able to give me on request.
> 
>> If you have it and you could ship it (a meter of 0.5-1mm wire
>> or so would be sufficient for me and I will give it back
>> after), I will be happy to test it.
> 
> Send me your address (off list) and I'll send you a meter for
> testing.
> 
> Best,
> Herbert
> 
>> Today I received the Sn99.3/Cu0.7 and I will post result soon.
> 
>> Best regards,
>> Andrea Baldoni
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