[volt-nuts] Poll

[Andreas Jahn]

Hello Frank,

thanks for your tips and especially the link to rhopoint.

>remember, that the LTZ circuitry attenuates all drifts of the 5 crucial 
>resistors by 1/100 (120, 1k, 13k) and by 1/300 (70k).
>So the Z201 resistors are a little bit overkill, 1-3 ppm/K for lower grade 
>metal foil or wirewound ones are sufficient for a low T.C. of the completed 
>circuit.

You are right.
on the other side my "lab" is not a thermally controlled room.
I have 18 degrees in winter and up to 33 degrees this summer.
Perhaps I will use two 25K of Z201 and the 70K of rhopoint.

>So, for the LTZ1000A you should set the temperature to 55°C at least, what 
>you obviously intended to do.

Ok thanks for reviewing my design.

>Two 25k in parallel over the 1k will do the job, don't they?

Yes. but one single resistor would cost less space
which makes it easier for mechanical/thermal decoupling of
the reference


>I will test the stability under rotation for my LTZ box this weekend,

thats more than I could expect. Thanks in advance.

> but the HP3458A stays where it is, sorry ;-)

I can understand this. And I swear that on the two Keithleys,
where I had access to, the effect was reversible with orientation.
At least for the resolution of 10uV in the 10V-Range.
Only the owner looked a little strange when I showed him
the accuracy of his instruments.

---

>Where did you get the Z201 from, did you order custom specific values, or 
>off-the-shelf?
They are catalog types from RS.

>What about the price and delivery time?
see link: (delivery from store)
http://de.rs-online.com/web/search/searchBrowseAction.html?method=searchProducts&searchTerm=z201&x=0&y=0

digikey also has some single values:
http://search.digikey.com/scripts/DkSearch/dksus.dll?Cat=66690&k=z201

They have also the UPW50-types  which I use for my first build with 3 ppm
(pre-aged with rated load for 2000 hours 1,5 hours on and 0,5 hours off at 
25 degrees)
They look much like the Rhopoint Economistors.
http://de.rs-online.com/web/search/searchBrowseAction.html?method=searchProducts&searchTerm=upw50&x=0&y=0

>I'm looking for the hermetically encapsulated/oil filled types as a 
>Standard Resistor.
I have heard that ECOMAL is a big Vishay distributor. (search for VHP)
http://www.ecomal.com/core.php?dat=Y29tcG9uZW50PWludmVudG9yeSZhY3Rpb249c2hvdyZ4SUQ9c2VhcmNoaW5nJmxhbmdJRD0x


>And did you order the LTZs at Linear in USA directly, or via distributor?

I ordered them by the "Bauteilbeschaffungsservice" of Conrad.
The Package is labeled by LTC with Distributor "Setron" as receiver.

best regards

Andreas