CS
Charles Steinmetz
Mon, Nov 23, 2015 10:26 PM
What is considered the break-over point of precision with low uncertainty
versus cost to a group like this? Is there a rule-of-thumb for the cost of
each additional digit of precision after N digits?
One person's opinion:
To a group like this, I'd be inclined to say that interest begins at
a room-temperature (say, 20C +/- 3C) accuracy of 3ppm (i.e.,
guaranteed to remain within 3ppm from 18-22C for at least one year
after purchase). 3 ppm is 0.0003%. There is at least one 10v
reference with specifications in this ballpark available at an asking
price under $130 (I'm told the seller has accepted offers
significantly lower than this).
If I sell someone a reference
that I've ascertained is 2.50163v @70.3 F with a calculated uncertainty, is
it valuable as a 0.1% reference even though the error may be much less,
like +/- 0.08%?
I, for one, do not consider 0.08% to be "much less" than 0.1%. One
sneeze and it's out of spec. Indeed, I would consider a claim of
0.1% accuracy to be bordering on fraudulent based on a calibrated
measurement at 0.08%, unless the spec was qualified as "within 0.1%
at [temperature within 0.1C] as is, where is -- no claim as to
accuracy after it has been shipped to the buyer."
Speaking as someone with substantial commercial design experience, I
would never offer a voltage reference for sale as a claimed "0.1%
standard" that I did not have excellent justification for believing
would stay below 0.05% for a year over a several-degree range of
temperature and multiple trips across the country via commercial
carriers. I wouldn't expect to be able to charge more than $10-15
for the product just described, and then only if the nominal output
voltage were 10v (I think you will find that there is a very strong
preference for 10v references over 5v, 2.5v, or other voltages).
Best regards,
Charles
Russ wrote:
>What is considered the break-over point of precision with low uncertainty
>versus cost to a group like this? Is there a rule-of-thumb for the cost of
>each additional digit of precision after N digits?
One person's opinion:
To a group like this, I'd be inclined to say that interest begins at
a room-temperature (say, 20C +/- 3C) accuracy of 3ppm (i.e.,
guaranteed to remain within 3ppm from 18-22C for at least one year
after purchase). 3 ppm is 0.0003%. There is at least one 10v
reference with specifications in this ballpark available at an asking
price under $130 (I'm told the seller has accepted offers
significantly lower than this).
>If I sell someone a reference
>that I've ascertained is 2.50163v @70.3 F with a calculated uncertainty, is
>it valuable as a 0.1% reference even though the error may be much less,
>like +/- 0.08%?
I, for one, do not consider 0.08% to be "much less" than 0.1%. One
sneeze and it's out of spec. Indeed, I would consider a claim of
0.1% accuracy to be bordering on fraudulent based on a calibrated
measurement at 0.08%, unless the spec was qualified as "within 0.1%
at [temperature within 0.1C] as is, where is -- no claim as to
accuracy after it has been shipped to the buyer."
Speaking as someone with substantial commercial design experience, I
would never offer a voltage reference for sale as a claimed "0.1%
standard" that I did not have excellent justification for believing
would stay below 0.05% for a year over a several-degree range of
temperature and multiple trips across the country via commercial
carriers. I wouldn't expect to be able to charge more than $10-15
for the product just described, and then only if the nominal output
voltage were 10v (I think you will find that there is a very strong
preference for 10v references over 5v, 2.5v, or other voltages).
Best regards,
Charles
RR
Russ Ramirez
Mon, Nov 23, 2015 10:41 PM
Excellent points, especially the consideration of shipment effects
year-round and across major temperature variations. Thank-you Charles.
Russ
On Mon, Nov 23, 2015 at 4:26 PM, Charles Steinmetz csteinmetz@yandex.com
wrote:
Russ wrote:
What is considered the break-over point of precision with low uncertainty
versus cost to a group like this? Is there a rule-of-thumb for the cost of
each additional digit of precision after N digits?
One person's opinion:
To a group like this, I'd be inclined to say that interest begins at a
room-temperature (say, 20C +/- 3C) accuracy of 3ppm (i.e., guaranteed to
remain within 3ppm from 18-22C for at least one year after purchase). 3
ppm is 0.0003%. There is at least one 10v reference with specifications in
this ballpark available at an asking price under $130 (I'm told the seller
has accepted offers significantly lower than this).
If I sell someone a reference
that I've ascertained is 2.50163v @70.3 F with a calculated uncertainty,
is
it valuable as a 0.1% reference even though the error may be much less,
like +/- 0.08%?
I, for one, do not consider 0.08% to be "much less" than 0.1%. One sneeze
and it's out of spec. Indeed, I would consider a claim of 0.1% accuracy to
be bordering on fraudulent based on a calibrated measurement at 0.08%,
unless the spec was qualified as "within 0.1% at [temperature within 0.1C]
as is, where is -- no claim as to accuracy after it has been shipped to the
buyer."
Speaking as someone with substantial commercial design experience, I would
never offer a voltage reference for sale as a claimed "0.1% standard" that
I did not have excellent justification for believing would stay below 0.05%
for a year over a several-degree range of temperature and multiple trips
across the country via commercial carriers. I wouldn't expect to be able
to charge more than $10-15 for the product just described, and then only if
the nominal output voltage were 10v (I think you will find that there is a
very strong preference for 10v references over 5v, 2.5v, or other voltages).
Best regards,
Charles
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.
Excellent points, especially the consideration of shipment effects
year-round and across major temperature variations. Thank-you Charles.
Russ
On Mon, Nov 23, 2015 at 4:26 PM, Charles Steinmetz <csteinmetz@yandex.com>
wrote:
> Russ wrote:
>
> What is considered the break-over point of precision with low uncertainty
>> versus cost to a group like this? Is there a rule-of-thumb for the cost of
>> each additional digit of precision after N digits?
>>
>
> One person's opinion:
>
> To a group like this, I'd be inclined to say that interest begins at a
> room-temperature (say, 20C +/- 3C) accuracy of 3ppm (i.e., guaranteed to
> remain within 3ppm from 18-22C for at least one year after purchase). 3
> ppm is 0.0003%. There is at least one 10v reference with specifications in
> this ballpark available at an asking price under $130 (I'm told the seller
> has accepted offers significantly lower than this).
>
> If I sell someone a reference
>> that I've ascertained is 2.50163v @70.3 F with a calculated uncertainty,
>> is
>> it valuable as a 0.1% reference even though the error may be much less,
>> like +/- 0.08%?
>>
>
> I, for one, do not consider 0.08% to be "much less" than 0.1%. One sneeze
> and it's out of spec. Indeed, I would consider a claim of 0.1% accuracy to
> be bordering on fraudulent based on a calibrated measurement at 0.08%,
> unless the spec was qualified as "within 0.1% at [temperature within 0.1C]
> as is, where is -- no claim as to accuracy after it has been shipped to the
> buyer."
>
> Speaking as someone with substantial commercial design experience, I would
> never offer a voltage reference for sale as a claimed "0.1% standard" that
> I did not have excellent justification for believing would stay below 0.05%
> for a year over a several-degree range of temperature and multiple trips
> across the country via commercial carriers. I wouldn't expect to be able
> to charge more than $10-15 for the product just described, and then only if
> the nominal output voltage were 10v (I think you will find that there is a
> very strong preference for 10v references over 5v, 2.5v, or other voltages).
>
> Best regards,
>
> Charles
>
>
> _______________________________________________
> 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.
>
A
acbern@gmx.de
Tue, Nov 24, 2015 8:35 AM
Charles and group,
another persons opinion:
I guess the reference to the "standards" means those sold on ebay US. If so, I would think it is a false expectation this would meet 3ppm acc. guaranteed within a year.
There is a lengthy chat in eevblog about it, in case you are not aware, and while the unit typically may not be too bad, it is certainly not seriously a 3ppm guaranteed standard (even in its best version). It starts with the traceability, and goes on with the design and build standard. Details in the blog. In summary, it is not even really spec'ed, also because it can't be (at least not close to what it seems to raise in expectations). But at that price, it would be unfair to expect more than a hobbyist item with relatively unclear real specs. But if you mean another item, let us know, I guess the group would be interested.
Keep in mind, the Fluke 732B is specified/guaranteed to 2ppm per year. There is data available from Fluke about 732B drifts ("Predictability of Solid State Zener References"), and it can be seen how hard it is for them to guarantee 2ppm/year.
So I think your price target and spec expectation ("guaranteed to remain"...) just does not match.
I would think a unit that has a traceable specification to a National Standard (including an error propagation analysis for the factory calibration how to get there), and be within say 5ppm a year, over a defined (limited) temperature range, with a good build standard (CU-TE spades, metal case, EMI filtering, PSU...), targeted at those who cannot afford/do not need a 732B could easily have a fair price of a couple hundred usd.
Other opinions welcome.
Cheers
Adrian
Gesendet: Montag, 23. November 2015 um 23:26 Uhr
Von: "Charles Steinmetz" csteinmetz@yandex.com
An: "Discussion of precise voltage measurement" volt-nuts@febo.com
Betreff: Re: [volt-nuts] Low-cost voltage reference questions
Russ wrote:
What is considered the break-over point of precision with low uncertainty
versus cost to a group like this? Is there a rule-of-thumb for the cost of
each additional digit of precision after N digits?
One person's opinion:
To a group like this, I'd be inclined to say that interest begins at
a room-temperature (say, 20C +/- 3C) accuracy of 3ppm (i.e.,
guaranteed to remain within 3ppm from 18-22C for at least one year
after purchase). 3 ppm is 0.0003%. There is at least one 10v
reference with specifications in this ballpark available at an asking
price under $130 (I'm told the seller has accepted offers
significantly lower than this).
If I sell someone a reference
that I've ascertained is 2.50163v @70.3 F with a calculated uncertainty, is
it valuable as a 0.1% reference even though the error may be much less,
like +/- 0.08%?
I, for one, do not consider 0.08% to be "much less" than 0.1%. One
sneeze and it's out of spec. Indeed, I would consider a claim of
0.1% accuracy to be bordering on fraudulent based on a calibrated
measurement at 0.08%, unless the spec was qualified as "within 0.1%
at [temperature within 0.1C] as is, where is -- no claim as to
accuracy after it has been shipped to the buyer."
Speaking as someone with substantial commercial design experience, I
would never offer a voltage reference for sale as a claimed "0.1%
standard" that I did not have excellent justification for believing
would stay below 0.05% for a year over a several-degree range of
temperature and multiple trips across the country via commercial
carriers. I wouldn't expect to be able to charge more than $10-15
for the product just described, and then only if the nominal output
voltage were 10v (I think you will find that there is a very strong
preference for 10v references over 5v, 2.5v, or other voltages).
Best regards,
Charles
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.
Charles and group,
another persons opinion:
I guess the reference to the "standards" means those sold on ebay US. If so, I would think it is a false expectation this would meet 3ppm acc. guaranteed within a year.
There is a lengthy chat in eevblog about it, in case you are not aware, and while the unit typically may not be too bad, it is certainly not seriously a 3ppm guaranteed standard (even in its best version). It starts with the traceability, and goes on with the design and build standard. Details in the blog. In summary, it is not even really spec'ed, also because it can't be (at least not close to what it seems to raise in expectations). But at that price, it would be unfair to expect more than a hobbyist item with relatively unclear real specs. But if you mean another item, let us know, I guess the group would be interested.
Keep in mind, the Fluke 732B is specified/guaranteed to 2ppm per year. There is data available from Fluke about 732B drifts ("Predictability of Solid State Zener References"), and it can be seen how hard it is for them to guarantee 2ppm/year.
So I think your price target and spec expectation ("guaranteed to remain"...) just does not match.
I would think a unit that has a traceable specification to a National Standard (including an error propagation analysis for the factory calibration how to get there), and be within say 5ppm a year, over a defined (limited) temperature range, with a good build standard (CU-TE spades, metal case, EMI filtering, PSU...), targeted at those who cannot afford/do not need a 732B could easily have a fair price of a couple hundred usd.
Other opinions welcome.
Cheers
Adrian
> Gesendet: Montag, 23. November 2015 um 23:26 Uhr
> Von: "Charles Steinmetz" <csteinmetz@yandex.com>
> An: "Discussion of precise voltage measurement" <volt-nuts@febo.com>
> Betreff: Re: [volt-nuts] Low-cost voltage reference questions
>
> Russ wrote:
>
> >What is considered the break-over point of precision with low uncertainty
> >versus cost to a group like this? Is there a rule-of-thumb for the cost of
> >each additional digit of precision after N digits?
>
> One person's opinion:
>
> To a group like this, I'd be inclined to say that interest begins at
> a room-temperature (say, 20C +/- 3C) accuracy of 3ppm (i.e.,
> guaranteed to remain within 3ppm from 18-22C for at least one year
> after purchase). 3 ppm is 0.0003%. There is at least one 10v
> reference with specifications in this ballpark available at an asking
> price under $130 (I'm told the seller has accepted offers
> significantly lower than this).
>
> >If I sell someone a reference
> >that I've ascertained is 2.50163v @70.3 F with a calculated uncertainty, is
> >it valuable as a 0.1% reference even though the error may be much less,
> >like +/- 0.08%?
>
> I, for one, do not consider 0.08% to be "much less" than 0.1%. One
> sneeze and it's out of spec. Indeed, I would consider a claim of
> 0.1% accuracy to be bordering on fraudulent based on a calibrated
> measurement at 0.08%, unless the spec was qualified as "within 0.1%
> at [temperature within 0.1C] as is, where is -- no claim as to
> accuracy after it has been shipped to the buyer."
>
> Speaking as someone with substantial commercial design experience, I
> would never offer a voltage reference for sale as a claimed "0.1%
> standard" that I did not have excellent justification for believing
> would stay below 0.05% for a year over a several-degree range of
> temperature and multiple trips across the country via commercial
> carriers. I wouldn't expect to be able to charge more than $10-15
> for the product just described, and then only if the nominal output
> voltage were 10v (I think you will find that there is a very strong
> preference for 10v references over 5v, 2.5v, or other voltages).
>
> Best regards,
>
> Charles
>
>
> _______________________________________________
> 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.
>
IJ
Ian Johnston
Tue, Nov 24, 2015 9:05 AM
Hi all,
I can relate to this.......and only last night I was pouring over it
wondering what to do!
I have just designed a Handheld Precision Digital Voltage
Source.........LM399AH & uController controlled.
About to start selling them, and so I am writing the manual & spec sheet for
it.......but can't decide without a years worth of data & testing behind me
what figures to use!
I've got the reference, DAC and op-amp figures, all the tempo's I need etc
etc.
Hmmmm!
Ian.
-----Original Message-----
From: acbern@gmx.de
To: volt-nuts@febo.com
Date: Tue, 24 Nov 2015 09:35:24 +0100
Subject: Re: [volt-nuts] Low-cost voltage reference questions
Charles and group,
another persons opinion:
I guess the reference to the "standards" means those sold on ebay US. If so,
I would think it is a false expectation this would meet 3ppm acc. guaranteed
within a year.
There is a lengthy chat in eevblog about it, in case you are not aware, and
while the unit typically may not be too bad, it is certainly not seriously a
3ppm guaranteed standard (even in its best version). It starts with the
traceability, and goes on with the design and build standard. Details in the
blog. In summary, it is not even really spec'ed, also because it can't be
(at least not close to what it seems to raise in expectations). But at that
price, it would be unfair to expect more than a hobbyist item with
relatively unclear real specs. But if you mean another item, let us know, I
guess the group would be interested.
Keep in mind, the Fluke 732B is specified/guaranteed to 2ppm per year. There
is data available from Fluke about 732B drifts ("Predictability of Solid
State Zener References"), and it can be seen how hard it is for them to
guarantee 2ppm/year.
So I think your price target and spec expectation ("guaranteed to
remain"...) just does not match.
I would think a unit that has a traceable specification to a National
Standard (including an error propagation analysis for the factory
calibration how to get there), and be within say 5ppm a year, over a defined
(limited) temperature range, with a good build standard (CU-TE spades, metal
case, EMI filtering, PSU...), targeted at those who cannot afford/do not
need a 732B could easily have a fair price of a couple hundred usd.
Other opinions welcome.
Cheers
Adrian
Gesendet: Montag, 23. November 2015 um 23:26 Uhr
Von: "Charles Steinmetz" csteinmetz@yandex.com
An: "Discussion of precise voltage measurement" volt-nuts@febo.com
Betreff: Re: [volt-nuts] Low-cost voltage reference questions
Russ wrote:
What is considered the break-over point of precision with low uncertainty
versus cost to a group like this? Is there a rule-of-thumb for the cost
each additional digit of precision after N digits?
One person's opinion:
To a group like this, I'd be inclined to say that interest begins at
a room-temperature (say, 20C +/- 3C) accuracy of 3ppm (i.e.,
guaranteed to remain within 3ppm from 18-22C for at least one year
after purchase). 3 ppm is 0.0003%. There is at least one 10v
reference with specifications in this ballpark available at an asking
price under $130 (I'm told the seller has accepted offers
significantly lower than this).
If I sell someone a reference
that I've ascertained is 2.50163v @70.3 F with a calculated uncertainty,
it valuable as a 0.1% reference even though the error may be much less,
like +/- 0.08%?
I, for one, do not consider 0.08% to be "much less" than 0.1%. One
sneeze and it's out of spec. Indeed, I would consider a claim of
0.1% accuracy to be bordering on fraudulent based on a calibrated
measurement at 0.08%, unless the spec was qualified as "within 0.1%
at [temperature within 0.1C] as is, where is -- no claim as to
accuracy after it has been shipped to the buyer."
Speaking as someone with substantial commercial design experience, I
would never offer a voltage reference for sale as a claimed "0.1%
standard" that I did not have excellent justification for believing
would stay below 0.05% for a year over a several-degree range of
temperature and multiple trips across the country via commercial
carriers. I wouldn't expect to be able to charge more than $10-15
for the product just described, and then only if the nominal output
voltage were 10v (I think you will find that there is a very strong
preference for 10v references over 5v, 2.5v, or other voltages).
Best regards,
Charles
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to
and follow the instructions there.
Hi all,
I can relate to this.......and only last night I was pouring over it
wondering what to do!
I have just designed a Handheld Precision Digital Voltage
Source.........LM399AH & uController controlled.
About to start selling them, and so I am writing the manual & spec sheet for
it.......but can't decide without a years worth of data & testing behind me
what figures to use!
I've got the reference, DAC and op-amp figures, all the tempo's I need etc
etc.
Hmmmm!
Ian.
-----Original Message-----
From: acbern@gmx.de
To: volt-nuts@febo.com
Date: Tue, 24 Nov 2015 09:35:24 +0100
Subject: Re: [volt-nuts] Low-cost voltage reference questions
Charles and group,
another persons opinion:
I guess the reference to the "standards" means those sold on ebay US. If so,
I would think it is a false expectation this would meet 3ppm acc. guaranteed
within a year.
There is a lengthy chat in eevblog about it, in case you are not aware, and
while the unit typically may not be too bad, it is certainly not seriously a
3ppm guaranteed standard (even in its best version). It starts with the
traceability, and goes on with the design and build standard. Details in the
blog. In summary, it is not even really spec'ed, also because it can't be
(at least not close to what it seems to raise in expectations). But at that
price, it would be unfair to expect more than a hobbyist item with
relatively unclear real specs. But if you mean another item, let us know, I
guess the group would be interested.
Keep in mind, the Fluke 732B is specified/guaranteed to 2ppm per year. There
is data available from Fluke about 732B drifts ("Predictability of Solid
State Zener References"), and it can be seen how hard it is for them to
guarantee 2ppm/year.
So I think your price target and spec expectation ("guaranteed to
remain"...) just does not match.
I would think a unit that has a traceable specification to a National
Standard (including an error propagation analysis for the factory
calibration how to get there), and be within say 5ppm a year, over a defined
(limited) temperature range, with a good build standard (CU-TE spades, metal
case, EMI filtering, PSU...), targeted at those who cannot afford/do not
need a 732B could easily have a fair price of a couple hundred usd.
Other opinions welcome.
Cheers
Adrian
> Gesendet: Montag, 23. November 2015 um 23:26 Uhr
> Von: "Charles Steinmetz" <csteinmetz@yandex.com>
> An: "Discussion of precise voltage measurement" <volt-nuts@febo.com>
> Betreff: Re: [volt-nuts] Low-cost voltage reference questions
>
> Russ wrote:
>
> >What is considered the break-over point of precision with low uncertainty
> >versus cost to a group like this? Is there a rule-of-thumb for the cost
of
> >each additional digit of precision after N digits?
>
> One person's opinion:
>
> To a group like this, I'd be inclined to say that interest begins at
> a room-temperature (say, 20C +/- 3C) accuracy of 3ppm (i.e.,
> guaranteed to remain within 3ppm from 18-22C for at least one year
> after purchase). 3 ppm is 0.0003%. There is at least one 10v
> reference with specifications in this ballpark available at an asking
> price under $130 (I'm told the seller has accepted offers
> significantly lower than this).
>
> >If I sell someone a reference
> >that I've ascertained is 2.50163v @70.3 F with a calculated uncertainty,
is
> >it valuable as a 0.1% reference even though the error may be much less,
> >like +/- 0.08%?
>
> I, for one, do not consider 0.08% to be "much less" than 0.1%. One
> sneeze and it's out of spec. Indeed, I would consider a claim of
> 0.1% accuracy to be bordering on fraudulent based on a calibrated
> measurement at 0.08%, unless the spec was qualified as "within 0.1%
> at [temperature within 0.1C] as is, where is -- no claim as to
> accuracy after it has been shipped to the buyer."
>
> Speaking as someone with substantial commercial design experience, I
> would never offer a voltage reference for sale as a claimed "0.1%
> standard" that I did not have excellent justification for believing
> would stay below 0.05% for a year over a several-degree range of
> temperature and multiple trips across the country via commercial
> carriers. I wouldn't expect to be able to charge more than $10-15
> for the product just described, and then only if the nominal output
> voltage were 10v (I think you will find that there is a very strong
> preference for 10v references over 5v, 2.5v, or other voltages).
>
> Best regards,
>
> Charles
>
>
> _______________________________________________
> 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.
>
_______________________________________________
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and follow the instructions there.
[Sent by MDaemon Mail Server at IanJohnston.com]
AJ
Andreas Jahn
Tue, Nov 24, 2015 10:02 AM
Hello,
the below mentioned 3ppm/year are not easy to get (even with expensive
references).
Your selected parts are both band gap references. Which are poor
regarding long term stability + noise.
The best references (stability + noise) are buried zener references.
Plastic packages suffer from humidity effects. (even good references can
have 10-15 ppm shift over 30% rH change).
So with high demands you would need a hermetically sealed reference (at
best in metal can case)
Further effects are temperature hysteresis and mechanical stress from
the PCB (or soldering).
Practically you have to pre-age the references (6-12 months) and to sort
out the
less performing parts if you really want to go below 10 ppm stability.
Book recommendation:
Current Sources and Voltage References: A Design Reference for
Electronics Engineers (Linden T. Harrison)
With best regards
Andreas
Am 23.11.2015 um 23:41 schrieb Russ Ramirez:
Excellent points, especially the consideration of shipment effects
year-round and across major temperature variations. Thank-you Charles.
Russ
On Mon, Nov 23, 2015 at 4:26 PM, Charles Steinmetz csteinmetz@yandex.com
wrote:
Russ wrote:
What is considered the break-over point of precision with low uncertainty
versus cost to a group like this? Is there a rule-of-thumb for the cost of
each additional digit of precision after N digits?
One person's opinion:
To a group like this, I'd be inclined to say that interest begins at a
room-temperature (say, 20C +/- 3C) accuracy of 3ppm (i.e., guaranteed to
remain within 3ppm from 18-22C for at least one year after purchase). 3
ppm is 0.0003%. There is at least one 10v reference with specifications in
this ballpark available at an asking price under $130 (I'm told the seller
has accepted offers significantly lower than this).
If I sell someone a reference
that I've ascertained is 2.50163v @70.3 F with a calculated uncertainty,
is
it valuable as a 0.1% reference even though the error may be much less,
like +/- 0.08%?
I, for one, do not consider 0.08% to be "much less" than 0.1%. One sneeze
and it's out of spec. Indeed, I would consider a claim of 0.1% accuracy to
be bordering on fraudulent based on a calibrated measurement at 0.08%,
unless the spec was qualified as "within 0.1% at [temperature within 0.1C]
as is, where is -- no claim as to accuracy after it has been shipped to the
buyer."
Speaking as someone with substantial commercial design experience, I would
never offer a voltage reference for sale as a claimed "0.1% standard" that
I did not have excellent justification for believing would stay below 0.05%
for a year over a several-degree range of temperature and multiple trips
across the country via commercial carriers. I wouldn't expect to be able
to charge more than $10-15 for the product just described, and then only if
the nominal output voltage were 10v (I think you will find that there is a
very strong preference for 10v references over 5v, 2.5v, or other voltages).
Best regards,
Charles
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https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.
Hello,
the below mentioned 3ppm/year are not easy to get (even with expensive
references).
Your selected parts are both band gap references. Which are poor
regarding long term stability + noise.
The best references (stability + noise) are buried zener references.
Plastic packages suffer from humidity effects. (even good references can
have 10-15 ppm shift over 30% rH change).
So with high demands you would need a hermetically sealed reference (at
best in metal can case)
Further effects are temperature hysteresis and mechanical stress from
the PCB (or soldering).
Practically you have to pre-age the references (6-12 months) and to sort
out the
less performing parts if you really want to go below 10 ppm stability.
Book recommendation:
Current Sources and Voltage References: A Design Reference for
Electronics Engineers (Linden T. Harrison)
With best regards
Andreas
Am 23.11.2015 um 23:41 schrieb Russ Ramirez:
> Excellent points, especially the consideration of shipment effects
> year-round and across major temperature variations. Thank-you Charles.
>
> Russ
>
> On Mon, Nov 23, 2015 at 4:26 PM, Charles Steinmetz <csteinmetz@yandex.com>
> wrote:
>
>> Russ wrote:
>>
>> What is considered the break-over point of precision with low uncertainty
>>> versus cost to a group like this? Is there a rule-of-thumb for the cost of
>>> each additional digit of precision after N digits?
>>>
>> One person's opinion:
>>
>> To a group like this, I'd be inclined to say that interest begins at a
>> room-temperature (say, 20C +/- 3C) accuracy of 3ppm (i.e., guaranteed to
>> remain within 3ppm from 18-22C for at least one year after purchase). 3
>> ppm is 0.0003%. There is at least one 10v reference with specifications in
>> this ballpark available at an asking price under $130 (I'm told the seller
>> has accepted offers significantly lower than this).
>>
>> If I sell someone a reference
>>> that I've ascertained is 2.50163v @70.3 F with a calculated uncertainty,
>>> is
>>> it valuable as a 0.1% reference even though the error may be much less,
>>> like +/- 0.08%?
>>>
>> I, for one, do not consider 0.08% to be "much less" than 0.1%. One sneeze
>> and it's out of spec. Indeed, I would consider a claim of 0.1% accuracy to
>> be bordering on fraudulent based on a calibrated measurement at 0.08%,
>> unless the spec was qualified as "within 0.1% at [temperature within 0.1C]
>> as is, where is -- no claim as to accuracy after it has been shipped to the
>> buyer."
>>
>> Speaking as someone with substantial commercial design experience, I would
>> never offer a voltage reference for sale as a claimed "0.1% standard" that
>> I did not have excellent justification for believing would stay below 0.05%
>> for a year over a several-degree range of temperature and multiple trips
>> across the country via commercial carriers. I wouldn't expect to be able
>> to charge more than $10-15 for the product just described, and then only if
>> the nominal output voltage were 10v (I think you will find that there is a
>> very strong preference for 10v references over 5v, 2.5v, or other voltages).
>>
>> Best regards,
>>
>> Charles
>>
>>
>> _______________________________________________
>> 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.
>>
> _______________________________________________
> 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.
A
acbern@gmx.de
Tue, Nov 24, 2015 11:55 AM
There are many things to factor in. Drift of reference itself over time and temperature (399 is 1ppm/K worst case alone, over say 10K, i.e. 23C+/-5K). Drift of the gain setting resistor is critical (assuming you have an amp generating 10V out of the 399 output voltage). and so on.
Also, you need a precise reference to calibrate the units (low cal uncertainty and low drift).
Selection, statistical validation and aging is needed.
All doable but costly and more complicated than one might expect.
Thats why I think the target price has to be reasonable, any thoughts here?
Gesendet: Dienstag, 24. November 2015 um 10:05 Uhr
Von: "Ian Johnston" ian@ianjohnston.com
An: "Discussion of precise voltage measurement" volt-nuts@febo.com
Betreff: Re: [volt-nuts] Low-cost voltage reference questions
Hi all,
I can relate to this.......and only last night I was pouring over it
wondering what to do!
I have just designed a Handheld Precision Digital Voltage
Source.........LM399AH & uController controlled.
About to start selling them, and so I am writing the manual & spec sheet for
it.......but can't decide without a years worth of data & testing behind me
what figures to use!
I've got the reference, DAC and op-amp figures, all the tempo's I need etc
etc.
Hmmmm!
Ian.
-----Original Message-----
From: acbern@gmx.de
To: volt-nuts@febo.com
Date: Tue, 24 Nov 2015 09:35:24 +0100
Subject: Re: [volt-nuts] Low-cost voltage reference questions
Charles and group,
another persons opinion:
I guess the reference to the "standards" means those sold on ebay US. If so,
I would think it is a false expectation this would meet 3ppm acc. guaranteed
within a year.
There is a lengthy chat in eevblog about it, in case you are not aware, and
while the unit typically may not be too bad, it is certainly not seriously a
3ppm guaranteed standard (even in its best version). It starts with the
traceability, and goes on with the design and build standard. Details in the
blog. In summary, it is not even really spec'ed, also because it can't be
(at least not close to what it seems to raise in expectations). But at that
price, it would be unfair to expect more than a hobbyist item with
relatively unclear real specs. But if you mean another item, let us know, I
guess the group would be interested.
Keep in mind, the Fluke 732B is specified/guaranteed to 2ppm per year. There
is data available from Fluke about 732B drifts ("Predictability of Solid
State Zener References"), and it can be seen how hard it is for them to
guarantee 2ppm/year.
So I think your price target and spec expectation ("guaranteed to
remain"...) just does not match.
I would think a unit that has a traceable specification to a National
Standard (including an error propagation analysis for the factory
calibration how to get there), and be within say 5ppm a year, over a defined
(limited) temperature range, with a good build standard (CU-TE spades, metal
case, EMI filtering, PSU...), targeted at those who cannot afford/do not
need a 732B could easily have a fair price of a couple hundred usd.
Other opinions welcome.
Cheers
Adrian
Gesendet: Montag, 23. November 2015 um 23:26 Uhr
Von: "Charles Steinmetz" csteinmetz@yandex.com
An: "Discussion of precise voltage measurement" volt-nuts@febo.com
Betreff: Re: [volt-nuts] Low-cost voltage reference questions
Russ wrote:
What is considered the break-over point of precision with low uncertainty
versus cost to a group like this? Is there a rule-of-thumb for the cost
each additional digit of precision after N digits?
One person's opinion:
To a group like this, I'd be inclined to say that interest begins at
a room-temperature (say, 20C +/- 3C) accuracy of 3ppm (i.e.,
guaranteed to remain within 3ppm from 18-22C for at least one year
after purchase). 3 ppm is 0.0003%. There is at least one 10v
reference with specifications in this ballpark available at an asking
price under $130 (I'm told the seller has accepted offers
significantly lower than this).
If I sell someone a reference
that I've ascertained is 2.50163v @70.3 F with a calculated uncertainty,
it valuable as a 0.1% reference even though the error may be much less,
like +/- 0.08%?
I, for one, do not consider 0.08% to be "much less" than 0.1%. One
sneeze and it's out of spec. Indeed, I would consider a claim of
0.1% accuracy to be bordering on fraudulent based on a calibrated
measurement at 0.08%, unless the spec was qualified as "within 0.1%
at [temperature within 0.1C] as is, where is -- no claim as to
accuracy after it has been shipped to the buyer."
Speaking as someone with substantial commercial design experience, I
would never offer a voltage reference for sale as a claimed "0.1%
standard" that I did not have excellent justification for believing
would stay below 0.05% for a year over a several-degree range of
temperature and multiple trips across the country via commercial
carriers. I wouldn't expect to be able to charge more than $10-15
for the product just described, and then only if the nominal output
voltage were 10v (I think you will find that there is a very strong
preference for 10v references over 5v, 2.5v, or other voltages).
Best regards,
Charles
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to
and follow the instructions there.
There are many things to factor in. Drift of reference itself over time and temperature (399 is 1ppm/K worst case alone, over say 10K, i.e. 23C+/-5K). Drift of the gain setting resistor is critical (assuming you have an amp generating 10V out of the 399 output voltage). and so on.
Also, you need a precise reference to calibrate the units (low cal uncertainty and low drift).
Selection, statistical validation and aging is needed.
All doable but costly and more complicated than one might expect.
Thats why I think the target price has to be reasonable, any thoughts here?
> Gesendet: Dienstag, 24. November 2015 um 10:05 Uhr
> Von: "Ian Johnston" <ian@ianjohnston.com>
> An: "Discussion of precise voltage measurement" <volt-nuts@febo.com>
> Betreff: Re: [volt-nuts] Low-cost voltage reference questions
>
> Hi all,
>
> I can relate to this.......and only last night I was pouring over it
> wondering what to do!
>
> I have just designed a Handheld Precision Digital Voltage
> Source.........LM399AH & uController controlled.
>
> About to start selling them, and so I am writing the manual & spec sheet for
> it.......but can't decide without a years worth of data & testing behind me
> what figures to use!
> I've got the reference, DAC and op-amp figures, all the tempo's I need etc
> etc.
>
> Hmmmm!
>
> Ian.
>
>
>
> -----Original Message-----
> From: acbern@gmx.de
> To: volt-nuts@febo.com
> Date: Tue, 24 Nov 2015 09:35:24 +0100
> Subject: Re: [volt-nuts] Low-cost voltage reference questions
>
>
> Charles and group,
> another persons opinion:
>
> I guess the reference to the "standards" means those sold on ebay US. If so,
> I would think it is a false expectation this would meet 3ppm acc. guaranteed
> within a year.
> There is a lengthy chat in eevblog about it, in case you are not aware, and
> while the unit typically may not be too bad, it is certainly not seriously a
> 3ppm guaranteed standard (even in its best version). It starts with the
> traceability, and goes on with the design and build standard. Details in the
> blog. In summary, it is not even really spec'ed, also because it can't be
> (at least not close to what it seems to raise in expectations). But at that
> price, it would be unfair to expect more than a hobbyist item with
> relatively unclear real specs. But if you mean another item, let us know, I
> guess the group would be interested.
> Keep in mind, the Fluke 732B is specified/guaranteed to 2ppm per year. There
> is data available from Fluke about 732B drifts ("Predictability of Solid
> State Zener References"), and it can be seen how hard it is for them to
> guarantee 2ppm/year.
> So I think your price target and spec expectation ("guaranteed to
> remain"...) just does not match.
>
> I would think a unit that has a traceable specification to a National
> Standard (including an error propagation analysis for the factory
> calibration how to get there), and be within say 5ppm a year, over a defined
> (limited) temperature range, with a good build standard (CU-TE spades, metal
> case, EMI filtering, PSU...), targeted at those who cannot afford/do not
> need a 732B could easily have a fair price of a couple hundred usd.
> Other opinions welcome.
>
>
> Cheers
> Adrian
>
>
> > Gesendet: Montag, 23. November 2015 um 23:26 Uhr
> > Von: "Charles Steinmetz" <csteinmetz@yandex.com>
> > An: "Discussion of precise voltage measurement" <volt-nuts@febo.com>
> > Betreff: Re: [volt-nuts] Low-cost voltage reference questions
> >
> > Russ wrote:
> >
> > >What is considered the break-over point of precision with low uncertainty
> > >versus cost to a group like this? Is there a rule-of-thumb for the cost
> of
> > >each additional digit of precision after N digits?
> >
> > One person's opinion:
> >
> > To a group like this, I'd be inclined to say that interest begins at
> > a room-temperature (say, 20C +/- 3C) accuracy of 3ppm (i.e.,
> > guaranteed to remain within 3ppm from 18-22C for at least one year
> > after purchase). 3 ppm is 0.0003%. There is at least one 10v
> > reference with specifications in this ballpark available at an asking
> > price under $130 (I'm told the seller has accepted offers
> > significantly lower than this).
> >
> > >If I sell someone a reference
> > >that I've ascertained is 2.50163v @70.3 F with a calculated uncertainty,
> is
> > >it valuable as a 0.1% reference even though the error may be much less,
> > >like +/- 0.08%?
> >
> > I, for one, do not consider 0.08% to be "much less" than 0.1%. One
> > sneeze and it's out of spec. Indeed, I would consider a claim of
> > 0.1% accuracy to be bordering on fraudulent based on a calibrated
> > measurement at 0.08%, unless the spec was qualified as "within 0.1%
> > at [temperature within 0.1C] as is, where is -- no claim as to
> > accuracy after it has been shipped to the buyer."
> >
> > Speaking as someone with substantial commercial design experience, I
> > would never offer a voltage reference for sale as a claimed "0.1%
> > standard" that I did not have excellent justification for believing
> > would stay below 0.05% for a year over a several-degree range of
> > temperature and multiple trips across the country via commercial
> > carriers. I wouldn't expect to be able to charge more than $10-15
> > for the product just described, and then only if the nominal output
> > voltage were 10v (I think you will find that there is a very strong
> > preference for 10v references over 5v, 2.5v, or other voltages).
> >
> > Best regards,
> >
> > Charles
> >
> >
> > _______________________________________________
> > 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.
> >
> _______________________________________________
> 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.
>
>
>
>
> [Sent by MDaemon Mail Server at IanJohnston.com]
> _______________________________________________
> 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.
>
RR
Russ Ramirez
Tue, Nov 24, 2015 2:28 PM
Thank-you all for your valuable insights and the book reference Jahn. I can
see clearly now that doing such a project with a LM399 for example as a
learning project would be interesting. Designing the board to use the
MAX6126, and finding reasonably priced low tempco parts was a useful
exercise.
Russ
On Tue, Nov 24, 2015 at 5:55 AM, acbern@gmx.de wrote:
There are many things to factor in. Drift of reference itself over time
and temperature (399 is 1ppm/K worst case alone, over say 10K, i.e.
23C+/-5K). Drift of the gain setting resistor is critical (assuming you
have an amp generating 10V out of the 399 output voltage). and so on.
Also, you need a precise reference to calibrate the units (low cal
uncertainty and low drift).
Selection, statistical validation and aging is needed.
All doable but costly and more complicated than one might expect.
Thats why I think the target price has to be reasonable, any thoughts here?
Gesendet: Dienstag, 24. November 2015 um 10:05 Uhr
Von: "Ian Johnston" ian@ianjohnston.com
An: "Discussion of precise voltage measurement" volt-nuts@febo.com
Betreff: Re: [volt-nuts] Low-cost voltage reference questions
Hi all,
I can relate to this.......and only last night I was pouring over it
wondering what to do!
I have just designed a Handheld Precision Digital Voltage
Source.........LM399AH & uController controlled.
About to start selling them, and so I am writing the manual & spec sheet
it.......but can't decide without a years worth of data & testing behind
what figures to use!
I've got the reference, DAC and op-amp figures, all the tempo's I need
etc.
Hmmmm!
Ian.
-----Original Message-----
From: acbern@gmx.de
To: volt-nuts@febo.com
Date: Tue, 24 Nov 2015 09:35:24 +0100
Subject: Re: [volt-nuts] Low-cost voltage reference questions
Charles and group,
another persons opinion:
I guess the reference to the "standards" means those sold on ebay US. If
I would think it is a false expectation this would meet 3ppm acc.
within a year.
There is a lengthy chat in eevblog about it, in case you are not aware,
while the unit typically may not be too bad, it is certainly not
3ppm guaranteed standard (even in its best version). It starts with the
traceability, and goes on with the design and build standard. Details in
blog. In summary, it is not even really spec'ed, also because it can't be
(at least not close to what it seems to raise in expectations). But at
price, it would be unfair to expect more than a hobbyist item with
relatively unclear real specs. But if you mean another item, let us
guess the group would be interested.
Keep in mind, the Fluke 732B is specified/guaranteed to 2ppm per year.
is data available from Fluke about 732B drifts ("Predictability of Solid
State Zener References"), and it can be seen how hard it is for them to
guarantee 2ppm/year.
So I think your price target and spec expectation ("guaranteed to
remain"...) just does not match.
I would think a unit that has a traceable specification to a National
Standard (including an error propagation analysis for the factory
calibration how to get there), and be within say 5ppm a year, over a
(limited) temperature range, with a good build standard (CU-TE spades,
case, EMI filtering, PSU...), targeted at those who cannot afford/do not
need a 732B could easily have a fair price of a couple hundred usd.
Other opinions welcome.
Cheers
Adrian
Gesendet: Montag, 23. November 2015 um 23:26 Uhr
Von: "Charles Steinmetz" csteinmetz@yandex.com
An: "Discussion of precise voltage measurement" volt-nuts@febo.com
Betreff: Re: [volt-nuts] Low-cost voltage reference questions
Russ wrote:
What is considered the break-over point of precision with low
versus cost to a group like this? Is there a rule-of-thumb for the
each additional digit of precision after N digits?
One person's opinion:
To a group like this, I'd be inclined to say that interest begins at
a room-temperature (say, 20C +/- 3C) accuracy of 3ppm (i.e.,
guaranteed to remain within 3ppm from 18-22C for at least one year
after purchase). 3 ppm is 0.0003%. There is at least one 10v
reference with specifications in this ballpark available at an asking
price under $130 (I'm told the seller has accepted offers
significantly lower than this).
If I sell someone a reference
that I've ascertained is 2.50163v @70.3 F with a calculated
it valuable as a 0.1% reference even though the error may be much
I, for one, do not consider 0.08% to be "much less" than 0.1%. One
sneeze and it's out of spec. Indeed, I would consider a claim of
0.1% accuracy to be bordering on fraudulent based on a calibrated
measurement at 0.08%, unless the spec was qualified as "within 0.1%
at [temperature within 0.1C] as is, where is -- no claim as to
accuracy after it has been shipped to the buyer."
Speaking as someone with substantial commercial design experience, I
would never offer a voltage reference for sale as a claimed "0.1%
standard" that I did not have excellent justification for believing
would stay below 0.05% for a year over a several-degree range of
temperature and multiple trips across the country via commercial
carriers. I wouldn't expect to be able to charge more than $10-15
for the product just described, and then only if the nominal output
voltage were 10v (I think you will find that there is a very strong
preference for 10v references over 5v, 2.5v, or other voltages).
Best regards,
Charles
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to
and follow the instructions there.
and follow the instructions there.
Thank-you all for your valuable insights and the book reference Jahn. I can
see clearly now that doing such a project with a LM399 for example as a
learning project would be interesting. Designing the board to use the
MAX6126, and finding reasonably priced low tempco parts was a useful
exercise.
Russ
On Tue, Nov 24, 2015 at 5:55 AM, <acbern@gmx.de> wrote:
> There are many things to factor in. Drift of reference itself over time
> and temperature (399 is 1ppm/K worst case alone, over say 10K, i.e.
> 23C+/-5K). Drift of the gain setting resistor is critical (assuming you
> have an amp generating 10V out of the 399 output voltage). and so on.
> Also, you need a precise reference to calibrate the units (low cal
> uncertainty and low drift).
> Selection, statistical validation and aging is needed.
> All doable but costly and more complicated than one might expect.
>
> Thats why I think the target price has to be reasonable, any thoughts here?
>
>
>
>
> > Gesendet: Dienstag, 24. November 2015 um 10:05 Uhr
> > Von: "Ian Johnston" <ian@ianjohnston.com>
> > An: "Discussion of precise voltage measurement" <volt-nuts@febo.com>
> > Betreff: Re: [volt-nuts] Low-cost voltage reference questions
> >
> > Hi all,
> >
> > I can relate to this.......and only last night I was pouring over it
> > wondering what to do!
> >
> > I have just designed a Handheld Precision Digital Voltage
> > Source.........LM399AH & uController controlled.
> >
> > About to start selling them, and so I am writing the manual & spec sheet
> for
> > it.......but can't decide without a years worth of data & testing behind
> me
> > what figures to use!
> > I've got the reference, DAC and op-amp figures, all the tempo's I need
> etc
> > etc.
> >
> > Hmmmm!
> >
> > Ian.
> >
> >
> >
> > -----Original Message-----
> > From: acbern@gmx.de
> > To: volt-nuts@febo.com
> > Date: Tue, 24 Nov 2015 09:35:24 +0100
> > Subject: Re: [volt-nuts] Low-cost voltage reference questions
> >
> >
> > Charles and group,
> > another persons opinion:
> >
> > I guess the reference to the "standards" means those sold on ebay US. If
> so,
> > I would think it is a false expectation this would meet 3ppm acc.
> guaranteed
> > within a year.
> > There is a lengthy chat in eevblog about it, in case you are not aware,
> and
> > while the unit typically may not be too bad, it is certainly not
> seriously a
> > 3ppm guaranteed standard (even in its best version). It starts with the
> > traceability, and goes on with the design and build standard. Details in
> the
> > blog. In summary, it is not even really spec'ed, also because it can't be
> > (at least not close to what it seems to raise in expectations). But at
> that
> > price, it would be unfair to expect more than a hobbyist item with
> > relatively unclear real specs. But if you mean another item, let us
> know, I
> > guess the group would be interested.
> > Keep in mind, the Fluke 732B is specified/guaranteed to 2ppm per year.
> There
> > is data available from Fluke about 732B drifts ("Predictability of Solid
> > State Zener References"), and it can be seen how hard it is for them to
> > guarantee 2ppm/year.
> > So I think your price target and spec expectation ("guaranteed to
> > remain"...) just does not match.
> >
> > I would think a unit that has a traceable specification to a National
> > Standard (including an error propagation analysis for the factory
> > calibration how to get there), and be within say 5ppm a year, over a
> defined
> > (limited) temperature range, with a good build standard (CU-TE spades,
> metal
> > case, EMI filtering, PSU...), targeted at those who cannot afford/do not
> > need a 732B could easily have a fair price of a couple hundred usd.
> > Other opinions welcome.
> >
> >
> > Cheers
> > Adrian
> >
> >
> > > Gesendet: Montag, 23. November 2015 um 23:26 Uhr
> > > Von: "Charles Steinmetz" <csteinmetz@yandex.com>
> > > An: "Discussion of precise voltage measurement" <volt-nuts@febo.com>
> > > Betreff: Re: [volt-nuts] Low-cost voltage reference questions
> > >
> > > Russ wrote:
> > >
> > > >What is considered the break-over point of precision with low
> uncertainty
> > > >versus cost to a group like this? Is there a rule-of-thumb for the
> cost
> > of
> > > >each additional digit of precision after N digits?
> > >
> > > One person's opinion:
> > >
> > > To a group like this, I'd be inclined to say that interest begins at
> > > a room-temperature (say, 20C +/- 3C) accuracy of 3ppm (i.e.,
> > > guaranteed to remain within 3ppm from 18-22C for at least one year
> > > after purchase). 3 ppm is 0.0003%. There is at least one 10v
> > > reference with specifications in this ballpark available at an asking
> > > price under $130 (I'm told the seller has accepted offers
> > > significantly lower than this).
> > >
> > > >If I sell someone a reference
> > > >that I've ascertained is 2.50163v @70.3 F with a calculated
> uncertainty,
> > is
> > > >it valuable as a 0.1% reference even though the error may be much
> less,
> > > >like +/- 0.08%?
> > >
> > > I, for one, do not consider 0.08% to be "much less" than 0.1%. One
> > > sneeze and it's out of spec. Indeed, I would consider a claim of
> > > 0.1% accuracy to be bordering on fraudulent based on a calibrated
> > > measurement at 0.08%, unless the spec was qualified as "within 0.1%
> > > at [temperature within 0.1C] as is, where is -- no claim as to
> > > accuracy after it has been shipped to the buyer."
> > >
> > > Speaking as someone with substantial commercial design experience, I
> > > would never offer a voltage reference for sale as a claimed "0.1%
> > > standard" that I did not have excellent justification for believing
> > > would stay below 0.05% for a year over a several-degree range of
> > > temperature and multiple trips across the country via commercial
> > > carriers. I wouldn't expect to be able to charge more than $10-15
> > > for the product just described, and then only if the nominal output
> > > voltage were 10v (I think you will find that there is a very strong
> > > preference for 10v references over 5v, 2.5v, or other voltages).
> > >
> > > Best regards,
> > >
> > > Charles
> > >
> > >
> > > _______________________________________________
> > > 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.
> > >
> > _______________________________________________
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