[volt-nuts] Voltage Reference Mini-Oven

[m k]

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
> To: volt-nuts at febo.com
> Date: Thu, 15 Sep 2011 14:15:58 -0700
> Subject: [volt-nuts] Voltage Reference Mini-Oven
> 
> 
> 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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