[volt-nuts] Voltage Reference Mini-Oven

[zbigniew169]

I would e grateful for a copy of such documentation.

By the way; Weston saturated standard cells are still in use in our polish
equivalent of american NBS; they kept about 400 units in Glowny Urzad Miar
in Warsaw.
In 1937 modified Weston cell was build it has 11% Cd 15% Bi and remain Hg as
amalgamate. It had 13 ppm tempo almoust 5 time less than original Weston
cell. In 1964 Roger G. Bates wrote a paper regarding stability o a such
secondary standard; the EFM of such cell was 1.0188 V at 25 Cel.deg., Six
cells after 26 years changed their EMF average by 0.03 mV. Because I am
biochemist, so electrochemisty was slightly close to my interest. Sometimes
I am dreaming to build such a cell...

Best regards, from Warsaw,

2011/9/16 Fred Schneider <pa4tim at gmail.com>

> I have the original guildline enclosure with schematic. There is an oven in
> there and the circuit is rather straight forward using some tranistors.
> Maybe you can use this as an example. The saturated cells must be hold at 30
> degrees. They must kept vertical allways and viberation free. After moving
> them arround they need about two weeks to stabilize and do not use a 10M
> meter on them. Mine are from 1971 and still in very good shape.
>
> Fred PA4TIM
>
> Op 16 sep. 2011 om 00:03 heeft zbigniew169 <zbigniew169 at gmail.com> het
> volgende geschreven:
>
> > 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
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-- 
Zbyszek