[volt-nuts] Low Frequency noise on LTZ1000A and tempco of unheated LTZ

[Dr. Frank Stellmach]

Andreas,

I can confirm, that the unstabilized LTZ1000 has a TC of around 50ppm/K.

I did not try to use the 200Ohm resistor for tempco trimming, as this 
has other disadvantages.
I think, that the tempco depends on the absolute value of the Zener 
diode, and therefore a higher or lower total ref voltage may give lower TC.
But this would be too expensive to selct...

I also found a sensitivity / unstability due to grounding problems, 
especially the Temp.-stabilization circuit seems to be volatile.

When I made a 24h measurement, I have seen many glitches, jumps of about 
-5ppm which last for 10-30s, and then returning to the original value.

Perhaps those glitches are caused by the MUX switch of the DVM (34401A 
or 3458A).

If I ground the metal case of the unit, I see a permanent change of the 
output in the same order of magnitude.


I will test your hint implementing the 200nF cap, and will see, if this 
described sensitivity will be reduced.

Frank