I agree with Rob. I never heard about special solder from HP.
Bear in mind, it's not the thermal voltage itself, that causes
measurement error, it's the _difference_ between the two leads. It's
much more important to keep associated plugs and solder joints at the
same temperature! So if you solder the plus-joint with your own
soldering wire, solder the minus-joint, too. That makes sure, thermal
EMF will be the same at both joints and hence compensate one each other.
As I mentioned before, I compared 24bit streams from two 34401A over
many days. The DMMs were at their highest sensitivity, one of them was
fixed by soldering an input relay with usual Sn60Pb40. The curves ran
absolutely parallel when the room temp changed. If there had been an
issue with the thermal EMF, the 6.5 digit DMM would have been able to
measure those voltages with ease.
So either the EMF difference isn't measurable (because temp at both
relay pins change synchronously), or HP didn't use special solder.
I wouldn't go the way of using special solder, except Fluke would
recommend it explicitly.
What about asking Fluke itself?
Volker
Am 13.08.2013 21:38, schrieb Rob Klein:
Op 13-8-2013 20:16, Joseph Gray schreef:
I came across a couple of old Fluke differential voltmeters that need
some
work. I thought it would be best to use low thermal EMF solder on these.
I think it would be best *not* to.
As far as I know, Fluke never used any low thermal EMF solder on any
of its equipment, even
the very top-of-the-range stuff. I certainly never seen it mentioned
in any service manual
for e.g. the 720, 845, 750, 752.
Rob.
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