[volt-nuts] Voltage Reference Mini-Oven

[zbigniew169]

He I am Zbigniew W. Kaminski from Warsaw Poland. I was member-observer up to
this time. I am user of Prema 6040D 7 & 1/2 digits multimeter.

I would be appreciate if You will send some details concerning construction
of Your mini-oven. I need something similar for Weston saturated standard
cell. In my case the stability must be even better than 0.1 Celsjus degree,
because of Weston temco in the range about 50 ppm. I think that in my
project I should use patinium resistor rathen than termistor, because it's
much long term stable than termistor. Platinium element is much less
sensitive to temperature, therefore the cuircuit  will be much complicated.
I am an owner of single Weston cell which stays in my lab during last 20
years, and I am curious how stable it is.

2011/9/15 WarrenS <warrensjmail-one at yahoo.com>

>
> It is well known that by changing the nominal operating current of a 1N825
> type reference diode, that its voltage turn over temperature point can be
> moved.
> Usually the turn over temperature can be set to the nominal operating
> temperature,  there by giving a Zero TC reference voltage over a limited
> temperature range.
> For the parts I'm testing, the voltage changes less than 0.1 PPM with a 5
> deg F temperature variation, and 1PPM over a 20 deg F range when the zero TC
> current is set for room temperature.
> Not bad, but being an extreme Volt Nut, I always want to do better.
>
> Two ways to make it better, Add an X^2 (second order) temperature
> compensator or put the reference in an oven.
>
> What I did was make a very simple Mini-Oven using an 1N825, a glass
> thermister & a 1/4 resistor,
> all heat shrink together  in a small package about the size of a 1 watt
> resistor.
> Now by Appling about 1/8 W nominal power to the resistor from a simple
> temperature controller, the thermistor can be held at a constant
> Temperature.
> This allows setting it up so that normal temperature changes have true ZERO
> effect on the zero TCed zener voltage.
> Next thing I want to make is a simple times 8/5 digital gain amp so that
> the gain resistors will have no effect when amplifying the 6.25x volt zener
>  up to 10.000000 Volts.
> (or times 10/7 for use with other types of voltage references)
>
> ws
>
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-- 
Zbyszek