[volt-nuts] Low EMF solder

[J. Forster]

When working with Eppley Thermopiles to directly measure optical power,
the signal is millivolts, at best. We had to use Keithley nanovoltmeters
with very low EMF wiring.

Keithley made special wiring kits that used unplated copper terminal lugs
and crimp joints. No solders at all.

I suspect similar terminals can be made by stripping the plating from
standard terminals.

-John

==============


> On this topic...
>
> I noticed a reference in Wikipedia to Pb90Sn10 being an alternative to
> cadmium solders; does anyone have better references on this?  (I'm finding
> the suggestion even in a 2007 Fluke brochure -- "Using Reference
> Multimeters for Precision Measurements" -- to use cadmium containing
> solders to build low thermal EMF leads, so I'm guessing there's just
> nothing that quite compares).
>
> Also, any suggestions on how to determine when older equipment uses Cd
> containing solders?  And how common is it in old test gear?
>
> I've been rehabilitating a significant number of old meters / scopes /
> etc
 both would like to get an idea of A) how likely it is that using PbSn
> solder (or PbAgSn solder) may significantly impact accuracy and B) how
> much more careful one needs to be when replacing components

>
> Thanks,
>
> -Tymm
>
>
> On Jan 21, 2013, at 10:27 AM, Dave M <dgminala at mediacombb.net> wrote:
>
>> Please excuse me for asking this... I'm sure it's been covered before,
>> but
>> without an easy way to search the archives, here goes.
>>
>> I'm repairing a couple of old Holt 323A Audio Voltage Standards, trying
>> to
>> make one good one out of two.  These instruments used to have small
>> hanks of
>> special low EMF solder to use on sensitive areas, but they have long
>> since
>> vanished from these units.  I've tried using Sn-Pb solders, but the
>> units go
>> into a tizzy when I use it.
>>
>> Does anyone know of a source where I could buy a few ounces of the
>> solder?
>> I think it's a Tin-Cadmium formula, but I guess that because of the
>> Cadmium
>> content, it's pretty much unobtanium now.  I'm sure that another formula
>> must exist that is currently being manufactured, but they want to sell a
>> bunch, not just a few ounces.
>>
>> Suggestions?
>>
>> Dave M
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