Re: gEDA-user: Design Lab Equipment

[John Griessen <john@xxxxxxxxxxxxxx>]

Steven Michalske wrote:

> > There's another reason for no plating.  What is that shiny plating on 
> > those commodity test leads?  Hmmm....
> > Laws of intermediate metals don't apply to mystery metals, do they?
>
> It applies to all metals, even alloys.  It is all to do with the vacuum 
> levels of the atoms and the alignment of the actual conduction bands.  
> This also works with semiconductors, Thermoelectric coolers use P and N 
> doped semiconductors to increase efficiency ( higher temperature per 
> volt or amp )

The case where they saw errors was noticing statistics using different kinds of leads
rather than noticing on one measurement.  They were measuring a kelvin bridge, so they
were taking measurements many inches apart, sometimes several feet apart.  So, if one
test lead was one alloy and one another, and they had a one degree temperature
difference, wouldn't they see a difference due to the one non-copper test lead and the temp difference
from it to the meter?

Would the difference go away when only copper is used throughout?

The testpoints they measured were copper also, and the system under test was connected by copper everywhere.

John Griessen

PS  I like Kai-Martin's amplifier idea better for some GPL kit hardware.

How about a version where you add an A2D
and ethernet to the diff amp!

And make a more expensive, but +/- 300V one.  The a +/- 700V one....  all GPL.
Selling as kits with howto's published under creative commons or GPL license
making all the liability severed from "consultant advice" and instead being zero liability
published information.


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