[volt-nuts] Sub PPM 10V transfer standard

[WB6BNQ]

Warren,

You need to do your schematics a little bit better.  Besides, I think you attached the wrong one.  There are a number of errors on the attached schematic.

Bill....WB6BNQ

WarrenS wrote:

> Want a stable 10V ref?
> Best thing to do is get a fluke 732A/B and  have it calibrated regularly for a few years.
> BUT
> For the Extreme (or cheap) Volt Nut, There is another choice.
> Attached is the circuit of a 0.1 PPM, 10 volt transfer standard.
>
> It has ONLY ONE critical part that limits its accuracy and stability.
> Everything else can be made to have so little effect as to be insignificant or else can be trimmed and calibrated out without using a precision voltage source using  a method similar to what the daily auto cal in the HP3458 does. It measures it's own internal 6+V reference.
>
> Every year or more, best to record the value of the nominal 6.2 volts, to measurement the ageing rate, by using a known external 10 volt standard.
> To do that, an accurate external way is needed to find the exact ratio of the 6.2 volts to the external 10 volt standard.
> This can be done by using a high resolution Linear DMM (aka HP3458A) OR a Kelvin-Varley divider (aka fluke 720 ) and null meter (aka Fluke 845).
> Lets assume if one wants to do 0.1 PPM things, then they have the equipment and skill needed to measure a 10v to 6v  ratio to 0.1 PPM.
> After that ratio is known and recorded the units internal 10 volts can then be set to that same ratio without further need of the external 10V standard.
>
> The main advantage of all this extra trouble is low cost accuracy and stability.
> There are no critical or expensive resistor needed or anything else critical, because all the TC and long term drift are canceled out whenever  a manual trim is done using an external ratio device to check its own 10 V against it's own 6.2 volts.
>
> Nothing very special is needed to build this beside care and time.
> To get the best performance, It  does take a lot of Nut-time to match and select things.
> Total parts cost with a well supplied analog junk box (or EBay) can be under $10.
>
> Any good 6V type reference device could be used.
> I'm using a well aged and selected 1n825 because I have a lot of history with them and they work good without an oven.
> I have not done any mailing test on these parts but they can be Zero TCed so that they do not change 0.1PPM over normal room temperature
> and they show no change when powered down for short periods of time and tend to return to their original value when hit with a heat gun and cold stray, so it makes a good part to start experimenting with.
>
> ws
>
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>    ws10Vref-9-3LR.gif    Type: GIF Image (image/gif)
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