[time-nuts] Some pics of the Datron 491x DC reference cell

Bruce Griffiths bruce.griffiths at xtra.co.nz
Sun Feb 1 22:46:48 UTC 2009

Dr. Frank Stellmach wrote:
> Bruce,
> good hint, I think you are right..
> Then it's a custom specific R array, metal foil technolgy (S105 or 
> similar) from Vishay, perhaps oil filled.
> Makes it very difficult to read the circuitry and design a replacement 
> with discrete resistors.
> Frank

The core circuit probably doesn't differ too much from the positive
reference circuit shown on the LTZ1000 datasheet.
It certainly wont be identical to the negative reference shown on that
datasheet which has the heater pins reversed (as shown it will cause a
large current to flow in the parasitic shunt diode connected across the
heater resistor).
NB use the latest datasheet which has a corrected schematic showing the
location and polarity of the parasitic diodes.


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