My first 10kOhm reference resistor

[ap]

The audiophooles have the same problem that they need to manufacture a copper post/plug, so they need copper tellurium too, but some abused it by making it mysterious. It is not, normal copper simply smears when milled. They could use brass just as well, but thats a different storry. Here, if you need low emf, Cu-Te is mandatory.

[quarks]

as discussed many times, Tellurium is not what makes a connector low emf.
CuTe is only used because of the bad machinabiltiy of pure copper.

[ap]

Yes, it actually makes EMF a little worse, just as beryllium in copper does when spring type plugs are needed, or the gold plating on CuTe posts, but its neglectable. Gets important in the nV range (see data proof spades or EM electronics contacts).

[BU508A]

So, it makes no difference at all to use Cu-Te or Cu-Be? It is "only" improving the machinability of Cu (as I read in some articles)?

This brings me to another question: If I have a binding post, core of pure copper or some Cu-alloy and it is plated with a thick Gold coating all around, would this not compensate the Seebeck effect, assumed, that we have nearly the same temp. everywhere?

---- current flow ----->

                     |~|***********|~|
---------------|~|***********|~|------------------
                     |~|***********|~|
---------------|~|***********|~|------------------
                     |~|***********|~|
                       ^          ^           ^
Cu-wire            |   Cu-alloy core  |           Cu-wire
                       |                         |
                 Gold coating----------'

And would this not mean, that I can still use these Hirschmann Gold plated binding posts? I do really like them.

[ap]

The temperature gradient across the gold layer is so small that no emf voltge issues are expectable (at this level). So with the hirschmanns, you essentially have copper to brass, and that you can measure

[BU508A]

Here is a little update to my reference resistor prototype.
I've putted an Arduino nano controller into it together with a sensor for temperature and humidity, which comes as an Arduino shield. The sensor itself is a SHT 21 from Sensirion (a Swiss company). The datasheet can be found above for download. The little red pcb is a level shifter between 3.3V and 5V for the I²C bus. It is bidirectional.
The prototype PCBs I'm usually using are from this company: http://www.roth-elektronik.com/en  - one can get them at Reichelt for example (https://secure.reichelt.de/)

I will attach the program listing of the nano here as well. Please be kind, I'm not a very good programmer. 

<placeholder for the bom, will follow>

And here are some pictures (and no, the wires aren't pure silver :-) )

[BU508A]

Here are some more pictures. This is the adapter case to do the connection between USB and the case (cases, there will be more) of the controller inside the resistor case. The case for the adapter was first used for another little project but I drilled one hole at the wrong place so I was reusing it here.