[volt-nuts] Voltage Reference Mini-Oven

WarrenS warrensjmail-one at yahoo.com
Thu Sep 15 22:56:15 UTC 2011


Of course the simple answer of how to take care of ALL the other 
uncertainties, is to just make a 6.2 volt reference such as something like 
the attached.
It need have NO other critical parts except the Zener that limit it's 
performance.
AND when using a good linear 8 digit voltmeter, a 6.2 volt ref can be as 
accurate as a 10 volt standard as a calibration point.

ws

*******
Hi Warren,

That does seem a very simple way to get the diode at a steady temp, but then 
you need to keep the rest steady to stop all the other uncertainties 
swamping the nice steady diode you have just created.

*********************

> From: 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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