[volt-nuts] What's All This Low Thermal EMF Test Lead Stuff?

Todd Micallef tmicallef at gmail.com
Tue Aug 19 16:12:37 EDT 2014


Stan,

I recently picked up some of these ...
http://www.douglasconnection.com/Furez-TSTWP30NP-Bare-Copper-Banana-Plug-Connectors-Pair-FZTSTWP30NP.htm

They are a little pricey and are made for 12ga wire. I think they are OK
for semi-permanent use. A lot of use will probably scratch the soft metal.
I plan on trying them with my Keithley 181 plugged into a low thermal
scanner.
The original Keithley cable will be difficult to terminate. I may have to
go with crimped spade lugs.

Also, I am all for joining a beer nuts group.

Todd


On Tue, Aug 19, 2014 at 2:07 AM, Stan Katz <stan.katz.hk at gmail.com> wrote:

> I'm a self described volt-nut-near-beer. I don't own a 732A/B, or an
> HP3458. I do own HP3456 DMMs that are at the top of my instrumentation
> pecking order.  I have all the necessary gear to calibrate these DMMs
> according to ancient HP documentation. At the top of my cal. chain is the
> 731B, called out in HP3456 original documentation.  This hierarchy places
> me in the near-beer, or junior member status of the group. I look forward
> to being educated, and/or corrected on my understanding of the use of test
> leads with precision instrumentation.
>
>  I don't find much ancient HP documentation on test leads. The only
> recommendations in the era of the 3456 back to the 1960's is to use as
> thick a solid lead of pure copper wire as you can find, and insert the wire
> into the drill hole on the banana terminal. If the copper is pure, and has
> been properly cleaned, the thermal emf's on both identical length leads
> should all be balanced, and cancel out. In any case, pure copper-copper
> connections generate the lowest thermal emf. I  will agree that manhandling
> 16 gauge solid wire can be very inconvenient.
>
>  The path I have taken recently is to order Nakamichi gold over copper
> stereo banana plugs for my connections ( I deal in low voltage work
> exclusively), as well as gold plated spade lugs to go under the banana
> screw-downs. ( My budget ruled out gold over beryllium copper Pomona brand
> spades. )  I will then experiment between the two connector types. As for
> connections, it seems to me the best course is just to screw down the
> banana plugs, or in the case of the spades, just crimp. I'll wing it on the
> crimping, and see if simple tools can perform adequately. I would avoid
> solder, since how can one form identical topological spots of solder on
> every connection, deposited at the exact same place on each connection, and
> ensure the exact same weight of solder, to the microgram, on each
> connection. Since my modus operandi is to aim for balanced emfs, I think
> solder is out. Of course, if one wishes to risk one's health, and that of
> the family, one can track down a source of cadmium, and mix up a lot of low
> thermal emf solder (cadmium solder is banned in the US, and EU)...not for
> me.
>
> Don't worry, I won't be using tin plated wire, I managed to pick up a spool
> of silver plated 16 gauge wire for my investigations.  Am I on some other
> planet for choosing the balanced thermal emf approach for precision test
> lead applications, as opposed to going to great lengths to eliminate every
> trace of emf?
>
> Please forgive me if these emf discussions have been between engineers
> working outdoors in the oil fields of North Dakota, or out on a North Sea
> drilling platform. In that case, go for all the super low emf techniques
> you can lay your hands on.
>
> Good Luck,
> Stan
> _______________________________________________
> volt-nuts mailing list -- volt-nuts at febo.com
> To unsubscribe, go to
> https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
> and follow the instructions there.
>


More information about the volt-nuts mailing list