Empathy List Archives

JS

Joel Setton

Thu, Dec 18, 2014 3:41 PM

Folks,

In my search for the Perfect Volt, I'm thinking about building a
reference voltage generator which would average the voltages generated
by 8 or 10 REF102CP chips (with a simple resistor network), mounted in a
temperature-controlled box.
Among all the experts on this list, does anyone have any experience with
such a project? It looks good on paper, but what kind of stability can I
reasonably expect?

Many thanks!

Joel Setton

Folks, In my search for the Perfect Volt, I'm thinking about building a reference voltage generator which would average the voltages generated by 8 or 10 REF102CP chips (with a simple resistor network), mounted in a temperature-controlled box. Among all the experts on this list, does anyone have any experience with such a project? It looks good on paper, but what kind of stability can I reasonably expect? Many thanks! Joel Setton

AJ

Andreas Jahn

Thu, Dec 18, 2014 6:53 PM

Hello,

I would expect a stability of around 10-15 ppm over one year after 6-12
months run in time.
The reason is that with the plastic package all references will have
about the same change in the order of 0.5ppm/% rH change.
So assumption is that you have maximum 30% rH change over one year.

With best regards

Andreas

Am 18.12.2014 um 16:41 schrieb Joel Setton:

Folks,

In my search for the Perfect Volt, I'm thinking about building a
reference voltage generator which would average the voltages generated
by 8 or 10 REF102CP chips (with a simple resistor network), mounted in
a temperature-controlled box.
Among all the experts on this list, does anyone have any experience
with such a project? It looks good on paper, but what kind of
stability can I reasonably expect?

Many thanks!

Joel Setton

volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Hello, I would expect a stability of around 10-15 ppm over one year after 6-12 months run in time. The reason is that with the plastic package all references will have about the same change in the order of 0.5ppm/% rH change. So assumption is that you have maximum 30% rH change over one year. With best regards Andreas Am 18.12.2014 um 16:41 schrieb Joel Setton: > Folks, > > In my search for the Perfect Volt, I'm thinking about building a > reference voltage generator which would average the voltages generated > by 8 or 10 REF102CP chips (with a simple resistor network), mounted in > a temperature-controlled box. > Among all the experts on this list, does anyone have any experience > with such a project? It looks good on paper, but what kind of > stability can I reasonably expect? > > Many thanks! > > Joel Setton > > > _______________________________________________ > volt-nuts mailing list -- volt-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > and follow the instructions there.

PK

Poul-Henning Kamp

Thu, Dec 18, 2014 7:05 PM

In message 5492F59E.8060808@free.fr, Joel Setton writes:

In my search for the Perfect Volt, I'm thinking about building a
reference voltage generator which would average the voltages generated
by 8 or 10 REF102CP chips (with a simple resistor network), mounted in a
temperature-controlled box.

The problem with averaging a bunch of the same type of chip is that
you cannot average out the systematic errors of that chip.

If you want to do it "right", you should average all sorts of
different (but obviously: good) chips, possibly assigning them
different weight depending on their qualities.

--
Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG | TCP/IP since RFC 956
FreeBSD committer | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.

-------- In message <5492F59E.8060808@free.fr>, Joel Setton writes: >In my search for the Perfect Volt, I'm thinking about building a >reference voltage generator which would average the voltages generated >by 8 or 10 REF102CP chips (with a simple resistor network), mounted in a >temperature-controlled box. The problem with averaging a bunch of the same type of chip is that you cannot average out the systematic errors of that chip. If you want to do it "right", you should average all sorts of different (but obviously: good) chips, possibly assigning them different weight depending on their qualities. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 phk@FreeBSD.ORG | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence.

DD

Dr. David Kirkby (Kirkby Microwave Ltd)

Thu, Dec 18, 2014 7:52 PM

On 18 Dec 2014 19:06, "Poul-Henning Kamp" phk@phk.freebsd.dk wrote:

In message 5492F59E.8060808@free.fr, Joel Setton writes:

In my search for the Perfect Volt, I'm thinking about building a
reference voltage generator which would average the voltages generated

If you want to do it "right", you should average all sorts of
different (but obviously: good) chips, possibly assigning them
different weight depending on their qualities.

I was aware of three 8.5 digit multimeters

Keysight 3458A
Fluke 8508A
Keithley 2002.

But

http://www.eevblog.com/forum/testgear/8-5-digit-dmm/

lists several others - some from manufacturers I have never heard of.

I would assume that they all use a state of the art voltage references. I
wonder if they all use the same method? If not, perhaps averaging those
would be one approach.

How would you average them? Assuming they are supposed to be the same
voltage, would it be OK to tie N output together with N resistors? Use low
value resistors on the references you trust most, and higher values on
those you trust least.

Dave

On 18 Dec 2014 19:06, "Poul-Henning Kamp" <phk@phk.freebsd.dk> wrote: > > -------- > In message <5492F59E.8060808@free.fr>, Joel Setton writes: > > >In my search for the Perfect Volt, I'm thinking about building a > >reference voltage generator which would average the voltages generated > If you want to do it "right", you should average all sorts of > different (but obviously: good) chips, possibly assigning them > different weight depending on their qualities. I was aware of three 8.5 digit multimeters * Keysight 3458A * Fluke 8508A * Keithley 2002. But http://www.eevblog.com/forum/testgear/8-5-digit-dmm/ lists several others - some from manufacturers I have never heard of. I would assume that they all use a state of the art voltage references. I wonder if they all use the same method? If not, perhaps averaging those would be one approach. How would you average them? Assuming they are supposed to be the same voltage, would it be OK to tie N output together with N resistors? Use low value resistors on the references you trust most, and higher values on those you trust least. Dave

JS

Joel Setton

Fri, Dec 19, 2014 11:17 AM

JS

Joel Setton

Fri, Dec 19, 2014 1:06 PM

JS

Joel Setton

Fri, Dec 19, 2014 5:17 PM

Guys,

Thanks for your comments! The idea is to use a simple resistor averaging
network, as shown in Fig. 14 of the REF102 datasheet.
I hadn't thought of the effect of relative humidity, would the
temperature-controlled enclosure at (say) 50C/122F change things in this
respect?
One nice thing about this circuit topology is that it's a simple matter
to measure the drift of each individual reference chip with respect to
the averaged output, even plot it over temperature.

At this time my biggest question is how to compute the total error
budget for such an arrangement. Any help would be appreciated!

Joel Setton

Guys, Thanks for your comments! The idea is to use a simple resistor averaging network, as shown in Fig. 14 of the REF102 datasheet. I hadn't thought of the effect of relative humidity, would the temperature-controlled enclosure at (say) 50C/122F change things in this respect? One nice thing about this circuit topology is that it's a simple matter to measure the drift of each individual reference chip with respect to the averaged output, even plot it over temperature. At this time my biggest question is how to compute the total error budget for such an arrangement. Any help would be appreciated! Joel Setton

volt-nuts@lists.febo.com

The "averaging reference"