Re: [volt-nuts] Matched resistors

[Randy Evans]

Andreas,

The current environment is an uncontrolled home lab.  Great variation in
temperature and humidity, hence the primary design will use the vhd200 oil
filled hermetic package resistor arrays.  I plan on evaluating for
stability and accuracy to see if I need to ovenize it to meet my voltage
standard needs. I plan on building one version type with LTZ1000s and
another with a LM399s for less demanding requirements.  The LTZ1000 will
definitely use the vhd200 resistor arrays and the LM399 may be able to use
the LTC5400 resistor arrays (or LTC1043).  The vhd200 is a leaded package
so should have minimal mechanical stress on the package (hopefully). If
necessary, and likely needed for the best stability, the circuit can be
ovenized.

Lots of testing to do.

Randy


On Sun, Jul 27, 2014 at 3:17 AM, Andreas Jahn 
wrote:

> Hello Randy,
>
> until now you have not written about your design accuracy needs and about
> your environment conditions.
> (humidity + temperature controlled lab or industrial environment or simply
> your uncontrolled "lab" at home).
>
> In your measurements you should also regard humidity as a significant
> factor
> especially with resistors in plastic package like the LTC5400.
> Also the epoxy pcb is creating mechanical stress due to humidity to the
> resistors
> which can change the resistor value if not proper mechanical decoupled.
> (Difficult to mandage with SMD parts).
>
> I know that humidity is not easy to measure. And time constants are more in
> the range of 4-7 days which makes it even more time consuming.
>
> My personal opinion is that a LTC1043 based desing will perform better than
> a desing with SMD metal film resistors like the LTC5400. And a shoot out
> between
> vhd200 and LTC1043 would also be interesting depending on temperature
> range.
>
> By the way. The term TC tracking which is used by the resistor
> manufacturers may
> be not the same that you expect in a lab condition.
> Usually T.C. of a resistor is measured at "3 cardinal points" -55 deg / 25
> deg / 125 deg.
> T.C. is then calculated out of these 3 values.
> You probably want to have the dR / dT tracking around 25 degrees which is
> not specified with this method.
> So if you specifiy T.C. tracking you should do this with your temperature
> range.
>
> I hope that we will get feedback on your results some day.
>
> With best regards
>
> Andreas
>
>
>
> Am 26.07.2014 17:56, schrieb Randy Evans:
>
>  I would like to thank all those you supplied ideas for matching resistors.
>>   I have decided to test three approaches for now, the first is using
>> Vishay
>> vhd200 hermetically sealed foil resistors (three each at around $26 each),
>> the second is using LTC5400 resistor arrays, the third is a hybrid
>> approach
>> using a Vishay vhd200 for the most critical resistor pair and LTC5400
>> resistor arrays for the other two, and the fourth will likely be a LTC1043
>> switch capacitor doubler  plus LTC5400s, although the latter is a lower
>> priority.
>>
>> I plan on characterizing them over time and temperature to see the effects
>> on output stability for the best approach considering cost, complexity,
>> and
>> accuracy.  Should be interesting if it works.  It's been taking longer
>> than
>> I wanted or hoped but there are only so many hours in the day and my day
>> job is interfering with my play time.
>>
>> Thanks for the help,
>>
>> Randy
>>
>>
>> On Fri, Jul 25, 2014 at 1:04 PM, Ivan.Cousins 
>> wrote:
>>
>>  Randy,
>>>
>>> You might want to look at:
>>>
>>> Digikey PN 749-1052-1-ND (qty 1, $0.89)
>>> or
>>> Digikey PN Y4485-5K/5KBCT-ND (qty 1, $22.93)
>>>
>>> Both parts are from Vishay.
>>>
>>>
>>> My advice is to build something and then measure that something.
>>>
>>> You are the best judge of your immediate design problem and measurement
>>> capabilities.
>>>
>>> I have found, after many years, that waiting for an "Expert" to hand you
>>> your answer does not work.
>>>
>>> No other "Expert" is as familiar with your present problem as you are.
>>>
>>> After a number of build-measure cycles, you may become the new "Expert".
>>>
>>> If one waits for the ultimate answer then you may wait forever.
>>>
>>> The art of engineering is to get close enough.
>>>
>>> One can remain in the "thinking" stage forever, it can become an endless
>>> loop.
>>>
>>> Once you start the project by building and then measuring, you will be on
>>> your way to an answer, your answer.
>>>
>>>
>>>
>>> I am reminded of a saying "everything is a transducer" used here before.
>>> The interactions in this case are the usual temperature, stress-strain,
>>> humidity, resistor metal migration, etc.
>>> Notice that I did not include time, (long term drift), on purpose.
>>> It could be explained by one of the above or other, measurable quantity
>>> over a measurement interval.
>>>
>>> This is meant in the best spirit possible.
>>> Best of luck in your project.
>>>
>>> John C.
>>>
>>> ___
>>> volt-nut

Re: [volt-nuts] Matched resistors

[Andreas Jahn]

Hello Randy,

until now you have not written about your design accuracy needs and 
about your environment conditions.
(humidity + temperature controlled lab or industrial environment or 
simply your uncontrolled "lab" at home).


In your measurements you should also regard humidity as a significant factor
especially with resistors in plastic package like the LTC5400.
Also the epoxy pcb is creating mechanical stress due to humidity to the 
resistors

which can change the resistor value if not proper mechanical decoupled.
(Difficult to mandage with SMD parts).

I know that humidity is not easy to measure. And time constants are more in
the range of 4-7 days which makes it even more time consuming.

My personal opinion is that a LTC1043 based desing will perform better than
a desing with SMD metal film resistors like the LTC5400. And a shoot out 
between

vhd200 and LTC1043 would also be interesting depending on temperature range.

By the way. The term TC tracking which is used by the resistor 
manufacturers may

be not the same that you expect in a lab condition.
Usually T.C. of a resistor is measured at "3 cardinal points" -55 deg / 
25 deg / 125 deg.

T.C. is then calculated out of these 3 values.
You probably want to have the dR / dT tracking around 25 degrees which 
is not specified with this method.
So if you specifiy T.C. tracking you should do this with your 
temperature range.


I hope that we will get feedback on your results some day.

With best regards

Andreas



Am 26.07.2014 17:56, schrieb Randy Evans:

I would like to thank all those you supplied ideas for matching resistors.
  I have decided to test three approaches for now, the first is using Vishay
vhd200 hermetically sealed foil resistors (three each at around $26 each),
the second is using LTC5400 resistor arrays, the third is a hybrid approach
using a Vishay vhd200 for the most critical resistor pair and LTC5400
resistor arrays for the other two, and the fourth will likely be a LTC1043
switch capacitor doubler  plus LTC5400s, although the latter is a lower
priority.

I plan on characterizing them over time and temperature to see the effects
on output stability for the best approach considering cost, complexity, and
accuracy.  Should be interesting if it works.  It's been taking longer than
I wanted or hoped but there are only so many hours in the day and my day
job is interfering with my play time.

Thanks for the help,

Randy


On Fri, Jul 25, 2014 at 1:04 PM, Ivan.Cousins 
wrote:


Randy,

You might want to look at:

Digikey PN 749-1052-1-ND (qty 1, $0.89)
or
Digikey PN Y4485-5K/5KBCT-ND (qty 1, $22.93)

Both parts are from Vishay.


My advice is to build something and then measure that something.

You are the best judge of your immediate design problem and measurement
capabilities.

I have found, after many years, that waiting for an "Expert" to hand you
your answer does not work.

No other "Expert" is as familiar with your present problem as you are.

After a number of build-measure cycles, you may become the new "Expert".

If one waits for the ultimate answer then you may wait forever.

The art of engineering is to get close enough.

One can remain in the "thinking" stage forever, it can become an endless
loop.

Once you start the project by building and then measuring, you will be on
your way to an answer, your answer.



I am reminded of a saying "everything is a transducer" used here before.
The interactions in this case are the usual temperature, stress-strain,
humidity, resistor metal migration, etc.
Notice that I did not include time, (long term drift), on purpose.
It could be explained by one of the above or other, measurable quantity
over a measurement interval.

This is meant in the best spirit possible.
Best of luck in your project.

John C.

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Re: [volt-nuts] Matched resistors

[Randy Evans]

I would like to thank all those you supplied ideas for matching resistors.
 I have decided to test three approaches for now, the first is using Vishay
vhd200 hermetically sealed foil resistors (three each at around $26 each),
the second is using LTC5400 resistor arrays, the third is a hybrid approach
using a Vishay vhd200 for the most critical resistor pair and LTC5400
resistor arrays for the other two, and the fourth will likely be a LTC1043
switch capacitor doubler  plus LTC5400s, although the latter is a lower
priority.

I plan on characterizing them over time and temperature to see the effects
on output stability for the best approach considering cost, complexity, and
accuracy.  Should be interesting if it works.  It's been taking longer than
I wanted or hoped but there are only so many hours in the day and my day
job is interfering with my play time.

Thanks for the help,

Randy


On Fri, Jul 25, 2014 at 1:04 PM, Ivan.Cousins 
wrote:

> Randy,
>
> You might want to look at:
>
> Digikey PN 749-1052-1-ND (qty 1, $0.89)
> or
> Digikey PN Y4485-5K/5KBCT-ND (qty 1, $22.93)
>
> Both parts are from Vishay.
>
>
> My advice is to build something and then measure that something.
>
> You are the best judge of your immediate design problem and measurement
> capabilities.
>
> I have found, after many years, that waiting for an "Expert" to hand you
> your answer does not work.
>
> No other "Expert" is as familiar with your present problem as you are.
>
> After a number of build-measure cycles, you may become the new "Expert".
>
> If one waits for the ultimate answer then you may wait forever.
>
> The art of engineering is to get close enough.
>
> One can remain in the "thinking" stage forever, it can become an endless
> loop.
>
> Once you start the project by building and then measuring, you will be on
> your way to an answer, your answer.
>
>
>
> I am reminded of a saying "everything is a transducer" used here before.
> The interactions in this case are the usual temperature, stress-strain,
> humidity, resistor metal migration, etc.
> Notice that I did not include time, (long term drift), on purpose.
> It could be explained by one of the above or other, measurable quantity
> over a measurement interval.
>
> This is meant in the best spirit possible.
> Best of luck in your project.
>
> John C.
>
> ___
> volt-nuts mailing list -- volt-nuts@febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/
> mailman/listinfo/volt-nuts
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Re: [volt-nuts] Matched resistors

[Ivan.Cousins]

Randy,

You might want to look at:

Digikey PN 749-1052-1-ND (qty 1, $0.89)
or
Digikey PN Y4485-5K/5KBCT-ND (qty 1, $22.93)

Both parts are from Vishay.


My advice is to build something and then measure that something.

You are the best judge of your immediate design problem and measurement 
capabilities.


I have found, after many years, that waiting for an "Expert" to hand you 
your answer does not work.


No other "Expert" is as familiar with your present problem as you are.

After a number of build-measure cycles, you may become the new "Expert".

If one waits for the ultimate answer then you may wait forever.

The art of engineering is to get close enough.

One can remain in the "thinking" stage forever, it can become an endless 
loop.


Once you start the project by building and then measuring, you will be 
on your way to an answer, your answer.




I am reminded of a saying "everything is a transducer" used here before.
The interactions in this case are the usual temperature, stress-strain, 
humidity, resistor metal migration, etc.

Notice that I did not include time, (long term drift), on purpose.
It could be explained by one of the above or other, measurable quantity 
over a measurement interval.


This is meant in the best spirit possible.
Best of luck in your project.

John C.
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Re: [volt-nuts] Matched resistors

[George Atkinson]

At risk of being flamed for suggesting scrapping an instrument, selecting
the best pair from the K-V divider of an old Null Voltmeter may be an
option. A simple bridge with the test resistors in a heated oil bath and
the other pair kept constant will give an indication of match. Take care
not to mechanically or thermally stress the resistors when removing them.
The resistors will have been well matched originally and will be well aged.

Robert G8RPI.


On 17 July 2014 05:40, Frank Stellmach  wrote:

> Randy,
>
> resistor matched in T.C. are extremely expensive, as the manufacturer (or
> yourself) would have to select these from a batch of many samples.
>
> reistors with very small T.C. (<1ppm/K) would do the job also, but they
> also need to be stable over time, in shelf life opereation mode, i.e.
> P<10mW.
>
> That means, you need those hermetically sealed VHP202Z from Vishay, T.C.
> is typically < 1ppm/K and they are stable to < 2ppm over 5years. But they
> cost already 80€ each, depending on tolerance.
>
> I made a longterm observation of these and found these parameters
> confirmed.
>
> Frank
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Re: [volt-nuts] Matched resistors

[Randy Evans]

Tony,

Sorry for not reading further.  I will give it some thought. Interesting
idea.

Randy


On Thu, Jul 24, 2014 at 5:13 AM, Tony Holt  wrote:

> Randy,
>
>
> On 24/07/2014 04:22, Randy Evans wrote:
>
>> Tony,
>>
>> Your improvement factor of SQRT(n) assumes that each resistor in the group
>> has random changes uncorrelated to all others in the group.  For similar
>> type resistors, I would think that is not likely to be true.
>>
>
> Yes/,/ I'm well aware of that which is why I discussed that point further
> down in my post. It was a long post though so I don't blame you for getting
> bored and not getting that far!
>
>
>  For shelf life
>> stability it is likely that they all "age" in a similar way.  Unless the
>> resistors are in a hermetic package, humidity would impact all the
>> resistors in a similar manner.
>>
>> Randy
>>
> Exactly. Since they are being used in a 1:1 divider configuration, if they
> age in a similar way, the tracking ratio stability will be good. The
> reality however is that there will be some variance between components, and
> using multiple resisters will reduce that overall variance. Part of the
> variance between individual resisters will likely follow a Guassian
> distribution and thus the improvement factor for that element will be
> SQRT(N).
>
> Some of the variance will likely be due to random factors which have a
> rather different distribution, probably highly skewed with long tails, and
> thus the improvement probably won't be SQRT(N). My conjecture (ok random
> speculation) is that factors such as stress differences due to
> microcracking in the ceramic substrate or at the terminations may cause
> some of the latter. Nevertheless, even though part of the variance doesn't
> follow SQRT(N) the variance will still reduce by using multiple identical
> resisters (if there are enough*). The problem is knowing how much - it
> probably can only be determined by lengthy experimentation, unless some
> good empirical data can be obtained from manufacturers or research papers.
>
> Another complication is that I believe that thin film resistor stability
> and TCR characteristics improve as the resistance reduces. This is not
> usually reflected in the datasheet but using multiple resistors in series
> allows lower values to be used which may perform better. On the other hand,
> thermal EMF problems may increase proportionally.
>
> TCR tracking is much easier to measure, so it might be interesting to see
> how it improves with increasing numbers of resisters. However, I understand
> that ratio stability is likely to be a bigger problem than TCR tracking.
>
> The other end of the spectrum, using a single Vishay VHD foil divider is
> certainly the simplest; however bear in mind that Vishay's stated typical
> tracking TCR of < .1ppm is just that, and the one that you buy may be
> anything but typical. And if you can work out the maximum tracking TCR from
> the VHD144/200 datasheet, you're a better man than I. My guess is that its
> probably better than .5ppm which is likely good enough for your
> application. But would it perform better than, say $30 worth of Vishay DFN,
> 3ppm 4-resister networks, 1 year shelf life ratio stability < 20ppm? I
> don't know.
>
> Of course there's nothing to stop you using multiple VHDs if you can get
> them at a good price. Ebay maybe?
>
> *) If all resisters are identical expcept that 1 in a 100 is markedly
> different, then any 10 will have a good chance (90%) of being identical;
> using 100 will have a good chance (64%) that at least one is different and
> thus the overall error would be at least 1/100 of the difference.
>
> Tony H
>
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Re: [volt-nuts] Matched resistors

[Tony Holt]

Randy,

On 24/07/2014 04:22, Randy Evans wrote:

Tony,

Your improvement factor of SQRT(n) assumes that each resistor in the group
has random changes uncorrelated to all others in the group.  For similar
type resistors, I would think that is not likely to be true.


Yes/,/ I'm well aware of that which is why I discussed that point 
further down in my post. It was a long post though so I don't blame you 
for getting bored and not getting that far!



For shelf life
stability it is likely that they all "age" in a similar way.  Unless the
resistors are in a hermetic package, humidity would impact all the
resistors in a similar manner.

Randy
Exactly. Since they are being used in a 1:1 divider configuration, if 
they age in a similar way, the tracking ratio stability will be good. 
The reality however is that there will be some variance between 
components, and using multiple resisters will reduce that overall 
variance. Part of the variance between individual resisters will likely 
follow a Guassian distribution and thus the improvement factor for that 
element will be SQRT(N).


Some of the variance will likely be due to random factors which have a 
rather different distribution, probably highly skewed with long tails, 
and thus the improvement probably won't be SQRT(N). My conjecture (ok 
random speculation) is that factors such as stress differences due to 
microcracking in the ceramic substrate or at the terminations may cause 
some of the latter. Nevertheless, even though part of the variance 
doesn't follow SQRT(N) the variance will still reduce by using multiple 
identical resisters (if there are enough*). The problem is knowing how 
much - it probably can only be determined by lengthy experimentation, 
unless some good empirical data can be obtained from manufacturers or 
research papers.


Another complication is that I believe that thin film resistor stability 
and TCR characteristics improve as the resistance reduces. This is not 
usually reflected in the datasheet but using multiple resistors in 
series allows lower values to be used which may perform better. On the 
other hand, thermal EMF problems may increase proportionally.


TCR tracking is much easier to measure, so it might be interesting to 
see how it improves with increasing numbers of resisters. However, I 
understand that ratio stability is likely to be a bigger problem than 
TCR tracking.


The other end of the spectrum, using a single Vishay VHD foil divider is 
certainly the simplest; however bear in mind that Vishay's stated 
typical tracking TCR of < .1ppm is just that, and the one that you buy 
may be anything but typical. And if you can work out the maximum 
tracking TCR from the VHD144/200 datasheet, you're a better man than I. 
My guess is that its probably better than .5ppm which is likely good 
enough for your application. But would it perform better than, say $30 
worth of Vishay DFN, 3ppm 4-resister networks, 1 year shelf life ratio 
stability < 20ppm? I don't know.


Of course there's nothing to stop you using multiple VHDs if you can get 
them at a good price. Ebay maybe?


*) If all resisters are identical expcept that 1 in a 100 is markedly 
different, then any 10 will have a good chance (90%) of being identical; 
using 100 will have a good chance (64%) that at least one is different 
and thus the overall error would be at least 1/100 of the difference.


Tony H
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Re: [volt-nuts] Matched resistors

[Charles Steinmetz]

Andreas wrote:


But for the 100uVpp I have to ask for the measurement conditions.
Is the source (reference) connected via (long cable) and supplied 
with another mains line


No


or on the same pcb with the same power supply (or battery supplied).


Yes.  (And I have extensive design experience with ultra-low noise 
power supplies, decoupling, RFI prevention, and low-noise grounding.)



Was the pcb cleaned before measurement to keep leakage low?


Yes, it was freshly built and cleaned upon completion (vapor-phase), 
although that really has no bearing on commutation noise (charge 
injection) internal to the switched capacitor circuit, which is where 
all of the cyclical noise is generated.  Can it be filtered 
out?  Perhaps, but not easily without raising some other noise or 
drift problem.


How much noise did the reference generate? 1uV output measurement is 
quite low with
typical 0.6ppm/V of a buried zener multiplied by 2 and a amplifier 
with 1.6uVpp (referred to input).


I was using the ADR4520 (1uVp-p noise in the 0.1-10Hz band), with 
post-filtering.  When I said "about 1uVpp" output noise, I was 
thinking order of magnitude for purposes of comparison to 100uV, not 
precise value (which was more like 2-3uVpp).


Best regards,

Charles



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Re: [volt-nuts] Matched resistors

[Dave M]

Do you have easy, low cost access to an old Fluke 801 or 803 differential 
voltmeter?  These meters have a Kelvin-Varley divider inside that is 
composed of strings of resistors that are highly matched in value and 
tempco.  If I remember correctly, the highest decade is filled with a string 
of 40K resistors, each succeeding smaller decade value is 1/5 of the next 
higher decade, but all very well matched. They should all be very well aged 
by now too. (Just like wine... they get better with age).
Perhaps you could mix & match values to come up with suitable resistors for 
your project.  If your project is a one-off deal, then perhaps that approach 
could prove viable.


Cheers,
Dave M



From: Tony 



Randy,

Have you considered using multiple identical resistors to reduce the
variance? Depending on who you believe, you can reduce the variance of
the overall resistance by SQRT(N) where N is the number of resistors
in series/parallel. Its not that easy to create a good search query
for
this but here is one such explanation:

http://paulorenato.com/joomla/index.php?option=com_content&view=article&id=109:combining-resistors-to-improve-tolerance&catid=4:projects&Itemid=4

Ideally they should all come from the same batch - ie. manufactured by
the same machine from the same batch of materials. Obviously there's
no
way to guarantee that without close liaison with the manufacturer (you
did want 10 million parts at $.10 each didn't you!) but hopefully a
set
of resistors which come off the same reel would come close.

The absolute value isn't important however, but 'statistical gain'
will also apply to the TCR and stability of the overall divider. The
following assumes that both factors are similarly improved by SQRT(N),
but in fact they may be rather better than that.

That80? or $108 for one sealed Vishay foil divider will buy a lot of
lower spec parts: 



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Re: [volt-nuts] Matched resistors

[Randy Evans]

Tony,

I should have mentioned that I am primarily referring to stability, not
accuracy.  As i stated before, accuracy is relatively unimportant but
stability is essential.

Randy


On Wed, Jul 23, 2014 at 8:22 PM, Randy Evans 
wrote:

> Tony,
>
> Your improvement factor of SQRT(n) assumes that each resistor in the group
> has random changes uncorrelated to all others in the group.  For similar
> type resistors, I would think that is not likely to be true. For shelf life
> stability it is likely that they all "age" in a similar way.  Unless the
> resistors are in a hermetic package, humidity would impact all the
> resistors in a similar manner.
>
> Randy
>
>
> On Wed, Jul 23, 2014 at 6:36 PM, Tony  wrote:
>
>> Randy,
>>
>> Have you considered using multiple identical resistors to reduce the
>> variance? Depending on who you believe, you can reduce the variance of the
>> overall resistance by SQRT(N) where N is the number of resistors in
>> series/parallel. Its not that easy to create a good search query for this
>> but here is one such explanation:
>>
>> http://paulorenato.com/joomla/index.php?option=com_content&;
>> view=article&id=109:combining-resistors-to-improve-
>> tolerance&catid=4:projects&Itemid=4
>>
>> Ideally they should all come from the same batch - ie. manufactured by
>> the same machine from the same batch of materials. Obviously there's no way
>> to guarantee that without close liaison with the manufacturer (you did want
>> 10 million parts at $.10 each didn't you!) but hopefully a set of resistors
>> which come off the same reel would come close.
>>
>> The absolute value isn't important however, but 'statistical gain' will
>> also apply to the TCR and stability of the overall divider. The following
>> assumes that both factors are similarly improved by SQRT(N), but in fact
>> they may be rather better than that.
>>
>> That80€ or $108 for one sealed Vishay foil divider will buy a lot of
>> lower spec parts:
>>
>> Approx 12558 x Susumu RR0510P .5%, 25ppm 0402 (Digikey, $86/10k). 6279 in
>> series and parallel in each leg of the 1:1 divider> com/photos/Susumu%20Photos/RR%200402%20SERIES.jpg> might reduce the
>> variance to 25ppm/SQRT(6279) = .32ppm. Can't see any spec for stability,
>> but it may also improve similarly. Would take a while to solder them onto
>> stripboard though!
>>
>> Slightly more sensible might be 1078 x TE Connectivity RP73 1%, 10ppm
>> 1206 (Digikey, $100.18/1K).  Stability .5% (no qualifers in datasheet)
>>  => 10ppm/SQRT(539) = .43ppm, stability => 215ppm
>>
>> Or 372 x KOA Speer RN731JTTD4021B5 .1%, 5ppm (Mouser, $29/100). Stability
>> not on data sheet but typical endurance is +/- .02% for 1000 hrs @ 70C
>> on/off 1.5hours/.5hours.
>> => 5ppm/SQRT(138) = .37ppm, endurance => 14.7ppm (Stability should be
>> rather better than that). Note that the Mouser part no. is for a 25ppm part
>> but their manufacturer's part number is the 5ppm part as is the
>> description. Also, the price is way too high for 25ppm parts.
>>
>> Or 28 x Susumu RG2012L .01%, 2ppm (Digikey, $39.6/10). Stability not
>> quoted but typical Load Life is .01% (1000 x 1.5hours on/.5hours off at 85C)
>> => 2ppm/SQRT(14) = .53ppm, endurance => 27ppm
>>
>> You could also use multiple resistor networks. Eg:
>>
>> 104 x Susumu RM2012B-103/103-PBVW10 .1%, 5ppm tracking, 2
>> resistors/device (Digikey $104/100). Stability not quoted, endurance 500ppm
>> (1000 x 1.5hours on/.5hours off at 85C)
>> => 5ppm/SQRT(104) = .49ppm, endurance => 49ppm
>>
>> 35 x TT Electronics SFN08B4701CBQLF7, .25%, 5ppm tracking 7
>> resistors/device (Digikey, $76/25) . Stability not quoted, high temperature
>> exposure < 1000ppm
>> => 5ppm/SQRT(122) = .52ppm
>>
>> 33 x TT Electronics 668A1001DLF .5%, 5ppm tracking 8resistors/device
>> (Digikey, $82/25). Stability not quoted, load life < 1000ppm
>> => 5ppm/SQRT(33 * 4) = .45ppm
>>
>> 16 x Vishay DFN .1%, 3ppm tracking with 4 resistors/device (Digikey,
>> $5.24/1). Shelf life ratio stability is specced at 20ppm (1 year at 25C).
>> (That may be a typical rather than a maximum - your parts may all be much
>> worse than typical). The 3ppm tracking TCR may also be a typical figure as
>> its headlined in a section titled 'TYPICAL PERFORMANCE' but in the
>> specification table its not qualified with '(typical)' as they sometimes do
>> in other datasheets. Its hard to tell.
>> => 3ppm/SQRT(32) = .53ppm shelf life stability => 3.5ppm
>>
>> 5 x Vishay DSMZ metal foil dividers, .5ppm tracking max (probably
>> performs rather better than this over restricted temperature range, but
>> don't believe the Vishay typical figure of < .1ppm/C) (Digikey, $22.93/1).
>> Shelf life ratio stability not quoted but 'typical limit' for Load Life
>> ratio stability is 50ppm (2000 hours at 70C). Who knows what a typical
>> limit is? Again, probably best to treat Vishay 'typical' figures with a
>> pinch of salt given the experience of another poster on volt-nuts.
>> => .5ppm/SQRT(5) = .22ppm

Re: [volt-nuts] Matched resistors

[Randy Evans]

Tony,

Your improvement factor of SQRT(n) assumes that each resistor in the group
has random changes uncorrelated to all others in the group.  For similar
type resistors, I would think that is not likely to be true. For shelf life
stability it is likely that they all "age" in a similar way.  Unless the
resistors are in a hermetic package, humidity would impact all the
resistors in a similar manner.

Randy


On Wed, Jul 23, 2014 at 6:36 PM, Tony  wrote:

> Randy,
>
> Have you considered using multiple identical resistors to reduce the
> variance? Depending on who you believe, you can reduce the variance of the
> overall resistance by SQRT(N) where N is the number of resistors in
> series/parallel. Its not that easy to create a good search query for this
> but here is one such explanation:
>
> http://paulorenato.com/joomla/index.php?option=com_content&;
> view=article&id=109:combining-resistors-to-improve-
> tolerance&catid=4:projects&Itemid=4
>
> Ideally they should all come from the same batch - ie. manufactured by the
> same machine from the same batch of materials. Obviously there's no way to
> guarantee that without close liaison with the manufacturer (you did want 10
> million parts at $.10 each didn't you!) but hopefully a set of resistors
> which come off the same reel would come close.
>
> The absolute value isn't important however, but 'statistical gain' will
> also apply to the TCR and stability of the overall divider. The following
> assumes that both factors are similarly improved by SQRT(N), but in fact
> they may be rather better than that.
>
> That80€ or $108 for one sealed Vishay foil divider will buy a lot of lower
> spec parts:
>
> Approx 12558 x Susumu RR0510P .5%, 25ppm 0402 (Digikey, $86/10k). 6279 in
> series and parallel in each leg of the 1:1 divider com/photos/Susumu%20Photos/RR%200402%20SERIES.jpg> might reduce the
> variance to 25ppm/SQRT(6279) = .32ppm. Can't see any spec for stability,
> but it may also improve similarly. Would take a while to solder them onto
> stripboard though!
>
> Slightly more sensible might be 1078 x TE Connectivity RP73 1%, 10ppm 1206
> (Digikey, $100.18/1K).  Stability .5% (no qualifers in datasheet)
>  => 10ppm/SQRT(539) = .43ppm, stability => 215ppm
>
> Or 372 x KOA Speer RN731JTTD4021B5 .1%, 5ppm (Mouser, $29/100). Stability
> not on data sheet but typical endurance is +/- .02% for 1000 hrs @ 70C
> on/off 1.5hours/.5hours.
> => 5ppm/SQRT(138) = .37ppm, endurance => 14.7ppm (Stability should be
> rather better than that). Note that the Mouser part no. is for a 25ppm part
> but their manufacturer's part number is the 5ppm part as is the
> description. Also, the price is way too high for 25ppm parts.
>
> Or 28 x Susumu RG2012L .01%, 2ppm (Digikey, $39.6/10). Stability not
> quoted but typical Load Life is .01% (1000 x 1.5hours on/.5hours off at 85C)
> => 2ppm/SQRT(14) = .53ppm, endurance => 27ppm
>
> You could also use multiple resistor networks. Eg:
>
> 104 x Susumu RM2012B-103/103-PBVW10 .1%, 5ppm tracking, 2 resistors/device
> (Digikey $104/100). Stability not quoted, endurance 500ppm (1000 x 1.5hours
> on/.5hours off at 85C)
> => 5ppm/SQRT(104) = .49ppm, endurance => 49ppm
>
> 35 x TT Electronics SFN08B4701CBQLF7, .25%, 5ppm tracking 7
> resistors/device (Digikey, $76/25) . Stability not quoted, high temperature
> exposure < 1000ppm
> => 5ppm/SQRT(122) = .52ppm
>
> 33 x TT Electronics 668A1001DLF .5%, 5ppm tracking 8resistors/device
> (Digikey, $82/25). Stability not quoted, load life < 1000ppm
> => 5ppm/SQRT(33 * 4) = .45ppm
>
> 16 x Vishay DFN .1%, 3ppm tracking with 4 resistors/device (Digikey,
> $5.24/1). Shelf life ratio stability is specced at 20ppm (1 year at 25C).
> (That may be a typical rather than a maximum - your parts may all be much
> worse than typical). The 3ppm tracking TCR may also be a typical figure as
> its headlined in a section titled 'TYPICAL PERFORMANCE' but in the
> specification table its not qualified with '(typical)' as they sometimes do
> in other datasheets. Its hard to tell.
> => 3ppm/SQRT(32) = .53ppm shelf life stability => 3.5ppm
>
> 5 x Vishay DSMZ metal foil dividers, .5ppm tracking max (probably performs
> rather better than this over restricted temperature range, but don't
> believe the Vishay typical figure of < .1ppm/C) (Digikey, $22.93/1). Shelf
> life ratio stability not quoted but 'typical limit' for Load Life ratio
> stability is 50ppm (2000 hours at 70C). Who knows what a typical limit is?
> Again, probably best to treat Vishay 'typical' figures with a pinch of salt
> given the experience of another poster on volt-nuts.
> => .5ppm/SQRT(5) = .22ppm, load life => 22ppm
>
> Interestingly Digikey quote a price of only $5400 for 1k parts for the
> similar DSM divider (1ppm tracking), which is a huge difference from
> $22.93. Might be worth considering a bulk buy if there enough volt-nuts
> with the same problem. They aren't stocked though so that price might not
> be 'real'. However:
> 

Re: [volt-nuts] Matched resistors

[Tony]

Randy,

Have you considered using multiple identical resistors to reduce the 
variance? Depending on who you believe, you can reduce the variance of 
the overall resistance by SQRT(N) where N is the number of resistors in 
series/parallel. Its not that easy to create a good search query for 
this but here is one such explanation:


http://paulorenato.com/joomla/index.php?option=com_content&view=article&id=109:combining-resistors-to-improve-tolerance&catid=4:projects&Itemid=4

Ideally they should all come from the same batch - ie. manufactured by 
the same machine from the same batch of materials. Obviously there's no 
way to guarantee that without close liaison with the manufacturer (you 
did want 10 million parts at $.10 each didn't you!) but hopefully a set 
of resistors which come off the same reel would come close.


The absolute value isn't important however, but 'statistical gain' will 
also apply to the TCR and stability of the overall divider. The 
following assumes that both factors are similarly improved by SQRT(N), 
but in fact they may be rather better than that.


That80€ or $108 for one sealed Vishay foil divider will buy a lot of 
lower spec parts:


Approx 12558 x Susumu RR0510P .5%, 25ppm 0402 (Digikey, $86/10k). 6279 
in series and parallel in each leg of the 1:1 
divider 
might reduce the variance to 25ppm/SQRT(6279) = .32ppm. Can't see any 
spec for stability, but it may also improve similarly. Would take a 
while to solder them onto stripboard though!


Slightly more sensible might be 1078 x TE Connectivity RP73 1%, 10ppm 
1206 (Digikey, $100.18/1K).  Stability .5% (no qualifers in datasheet)

 => 10ppm/SQRT(539) = .43ppm, stability => 215ppm

Or 372 x KOA Speer RN731JTTD4021B5 .1%, 5ppm (Mouser, $29/100). 
Stability not on data sheet but typical endurance is +/- .02% for 1000 
hrs @ 70C on/off 1.5hours/.5hours.
=> 5ppm/SQRT(138) = .37ppm, endurance => 14.7ppm (Stability should be 
rather better than that). Note that the Mouser part no. is for a 25ppm 
part but their manufacturer's part number is the 5ppm part as is the 
description. Also, the price is way too high for 25ppm parts.


Or 28 x Susumu RG2012L .01%, 2ppm (Digikey, $39.6/10). Stability not 
quoted but typical Load Life is .01% (1000 x 1.5hours on/.5hours off at 85C)

=> 2ppm/SQRT(14) = .53ppm, endurance => 27ppm

You could also use multiple resistor networks. Eg:

104 x Susumu RM2012B-103/103-PBVW10 .1%, 5ppm tracking, 2 
resistors/device (Digikey $104/100). Stability not quoted, endurance 
500ppm (1000 x 1.5hours on/.5hours off at 85C)

=> 5ppm/SQRT(104) = .49ppm, endurance => 49ppm

35 x TT Electronics SFN08B4701CBQLF7, .25%, 5ppm tracking 7 
resistors/device (Digikey, $76/25) . Stability not quoted, high 
temperature exposure < 1000ppm

=> 5ppm/SQRT(122) = .52ppm

33 x TT Electronics 668A1001DLF .5%, 5ppm tracking 8resistors/device 
(Digikey, $82/25). Stability not quoted, load life < 1000ppm

=> 5ppm/SQRT(33 * 4) = .45ppm

16 x Vishay DFN .1%, 3ppm tracking with 4 resistors/device (Digikey, 
$5.24/1). Shelf life ratio stability is specced at 20ppm (1 year at 
25C). (That may be a typical rather than a maximum - your parts may all 
be much worse than typical). The 3ppm tracking TCR may also be a typical 
figure as its headlined in a section titled 'TYPICAL PERFORMANCE' but in 
the specification table its not qualified with '(typical)' as they 
sometimes do in other datasheets. Its hard to tell.

=> 3ppm/SQRT(32) = .53ppm shelf life stability => 3.5ppm

5 x Vishay DSMZ metal foil dividers, .5ppm tracking max (probably 
performs rather better than this over restricted temperature range, but 
don't believe the Vishay typical figure of < .1ppm/C) (Digikey, 
$22.93/1). Shelf life ratio stability not quoted but 'typical limit' for 
Load Life ratio stability is 50ppm (2000 hours at 70C). Who knows what a 
typical limit is? Again, probably best to treat Vishay 'typical' figures 
with a pinch of salt given the experience of another poster on volt-nuts.

=> .5ppm/SQRT(5) = .22ppm, load life => 22ppm

Interestingly Digikey quote a price of only $5400 for 1k parts for the 
similar DSM divider (1ppm tracking), which is a huge difference from 
$22.93. Might be worth considering a bulk buy if there enough volt-nuts 
with the same problem. They aren't stocked though so that price might 
not be 'real'. However:
20 x Vishay DSM dividers, 1ppm (Digikey, $5400/1000) Load life ratio 
stability 'typical limit' 50ppm

=> 1ppm/SQRT(20) = .22ppm, load life => 11ppm

Multiple LT5400 networks could also be used and may give the best 
results, but the much larger absolute tolerance, +/-15% would cause 
those with the highest value for series connected/lowest for parallel to 
dominate and reduce the statistical improvement. Do your own calculations.


Its interesting that all these different components end up providing 
pretty much the same performance for the same cost - in ot

Re: [volt-nuts] Matched resistors

[Andreas Jahn]

Hello,

the 50uV loss is plausible to me.

But for the 100uVpp I have to ask for the measurement conditions.
Is the source (reference) connected via (long cable) and supplied with 
another mains line

 or on the same pcb with the same power supply (or battery supplied).
Was the pcb cleaned before measurement to keep leakage low?
How much noise did the reference generate? 1uV output measurement is 
quite low with
typical 0.6ppm/V of a buried zener multiplied by 2 and a amplifier with 
1.6uVpp (referred to input).


As every CMOS input is susceptible against noise (getting rectified over 
the input protection diodes)

you can easily shift the input voltage by an offset due to RF noise.
For LTC1043 inputs which are connected via external line I use a 1nF filter
capacitor against ground to keep the influence of the RF noise low.

With best regards

Andreas

Am 23.07.2014 02:40, schrieb Charles Steinmetz:

Randy wrote:

I agree that there are potentially some serious unknown issues with 
drift

due to time and temperature due to changes in leakage current, charge
injection, etc.  I would think some serious characterization would be
needed before this approach could be used.


I have used LTC1043s in the voltage-multiplier configuration, and 
based on that experience I believe you will find there are too many 
surprises hiding there to reach your error budget.  First, there are 
losses in the conversion -- IME, even when driving nothing but the 
non-inverting input of an LTC1050 chopper-stabilized opamp used as a 
follower, the output voltage of an LTC1043 doubler is quite a bit 
(50uV or more) less than [Vin * 2].  Second, the output of the 1043 + 
buffer is about 100x noisier than the output of the same reference 
followed by a non-inverting gain-of-two LTC1050 (on the order of 
100uVp-p for the 1043 + buffer, about 1uVp-p for the non-inverting 
gain-of-two amplifier in a 10Hz bandwidth, IME).  Also, the 1043 noise 
is not symmetrical, so different DC meters may give readings that 
differ by 50uV from one another.


If you try the LTC1043, I'll be interested to see what you find.

Best regards,

Charles



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Re: [volt-nuts] Matched resistors

[Randy Evans]

Charles,

For the design I am contemplating, the accuracy of the X2 in not important,
only the stability.  For example, if the output of the X2 is 50uV low, I
don't care so long as its always 50 uV low +/- a few ppm over time and
temperature.  The noise could be filtered but its must also be stable.
 Based on what I am hearing, the switched capacitor multiplier doesn't look
promising.

Randy


On Tue, Jul 22, 2014 at 5:40 PM, Charles Steinmetz 
wrote:

> Randy wrote:
>
>  I agree that there are potentially some serious unknown issues with drift
>> due to time and temperature due to changes in leakage current, charge
>> injection, etc.  I would think some serious characterization would be
>> needed before this approach could be used.
>>
>
> I have used LTC1043s in the voltage-multiplier configuration, and based on
> that experience I believe you will find there are too many surprises hiding
> there to reach your error budget.  First, there are losses in the
> conversion -- IME, even when driving nothing but the non-inverting input of
> an LTC1050 chopper-stabilized opamp used as a follower, the output voltage
> of an LTC1043 doubler is quite a bit (50uV or more) less than [Vin * 2].
>  Second, the output of the 1043 + buffer is about 100x noisier than the
> output of the same reference followed by a non-inverting gain-of-two
> LTC1050 (on the order of 100uVp-p for the 1043 + buffer, about 1uVp-p for
> the non-inverting gain-of-two amplifier in a 10Hz bandwidth, IME).  Also,
> the 1043 noise is not symmetrical, so different DC meters may give readings
> that differ by 50uV from one another.
>
> If you try the LTC1043, I'll be interested to see what you find.
>
> Best regards,
>
> Charles
>
>
>
>
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Re: [volt-nuts] Matched resistors

[Charles Steinmetz]

Randy wrote:


I agree that there are potentially some serious unknown issues with drift
due to time and temperature due to changes in leakage current, charge
injection, etc.  I would think some serious characterization would be
needed before this approach could be used.


I have used LTC1043s in the voltage-multiplier configuration, and 
based on that experience I believe you will find there are too many 
surprises hiding there to reach your error budget.  First, there are 
losses in the conversion -- IME, even when driving nothing but the 
non-inverting input of an LTC1050 chopper-stabilized opamp used as a 
follower, the output voltage of an LTC1043 doubler is quite a bit 
(50uV or more) less than [Vin * 2].  Second, the output of the 1043 + 
buffer is about 100x noisier than the output of the same reference 
followed by a non-inverting gain-of-two LTC1050 (on the order of 
100uVp-p for the 1043 + buffer, about 1uVp-p for the non-inverting 
gain-of-two amplifier in a 10Hz bandwidth, IME).  Also, the 1043 
noise is not symmetrical, so different DC meters may give readings 
that differ by 50uV from one another.


If you try the LTC1043, I'll be interested to see what you find.

Best regards,

Charles



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Re: [volt-nuts] Matched resistors

[Randy Evans]

I agree that there are potentially some serious unknown issues with drift
due to time and temperature due to changes in leakage current, charge
injection, etc.  I would think some serious characterization would be
needed before this approach could be used. One approach for the charge
injection is to try and have the input voltage near Vdd/2 so the charge
injection effects are nulled out.  I'm trying to figure out how to do that
for a X2 circuit.  Any ideas?

 I talked to Vishay and they, of course, could do the resistors and I am
awaiting a quote.  They stated they would have to "tune" the vhd200
resistor pair to have a very low (0.2ppm/C) ratio stability .  Doable but
potentially very expensive.  Unfortunately, the maximum value of the
resistors is 20Kohms which would greatly increase the power dissipation of
the resistors, not good for long term stability.  Still working the issue.

Randy


On Tue, Jul 22, 2014 at 8:12 AM,  wrote:

> and yes, I forgot: only down-dividing of course, so to reach 10V, two
> LTZ1000 would be needed in series. advantage is that noise statistically is
> reduced by factor of about 1.4. formally also applies to drift.
>
>
> > Gesendet: Montag, 21. Juli 2014 um 20:28 Uhr
> > Von: "Bob Smither" 
> > An: "Discussion of precise voltage measurement" 
> > Betreff: Re: [volt-nuts] Matched resistors
> >
> > On 07/17/2014 10:26 AM, Randy Evans wrote:
> > > Frank,
> > >
> > > The high cost is my concern, although high performance demands high
> price
> > > typically.  I am trying to double the voltage reference from either an
> > > LM399 or LTZ1000, hence the need for precision matched resistors for a
> x2
> > > non-inverting amplifier (using a LT1151 precision op amp).  An
> alternative
> > > I am investigating is using the LTC1043 in a voltage doubling circuit
> as
> > > shown in Linear Technology app note AN 42, page 6, Figure 16.  It
> states
> > > that Vout = 2xVin +/- 5 ppm.  I am less concerned about the absolute
> > > accuracy than I am about the long term stability.  I assume that a high
> > > quality capacitor is required (low leakage, low ESR, low dielectric
> > > absorbtion, etc.) but the circuit does not appear to be dependent on
> the
> > > absolute value of the capacitors.  I'm not sure if the two 1uF caps
>  need
> > > to be matched.  If they do then that would be a show stopper.
> > >
> > > Does anyone have any experience using the LTC1043 in such a circuit?
> >
> > Hi Randy,
> >
> > There are some other error sources that might need to be considered when
> using
> > the LTC1043.
> >
> > I have not used the LTC1043, but note that on the data sheet there is a
> small
> > charge injection at each of the switch pins. In the multiply by 2
> circuit shown
> > on the data sheet they are using 1 ufd caps.  Typical charge injection
> (depends
> > on voltage level) is 8 pC. With the 1 ufd caps this is 8 uV.  I assume
> there is
> > some offsetting effect - but this might be a significant contributor to
> the 5
> > ppm error that is mentioned.
> >
> > There is also a 6 nA (typical) leakage mentioned.  During the "hold"
> time (
> > about 1 msec) of the output 1 ufd cap this comes to 6 uV.
> >
> > Regards,
> > Bob Smither
> >
> > ___
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Re: [volt-nuts] Matched resistors

[acbern]

and yes, I forgot: only down-dividing of course, so to reach 10V, two LTZ1000 
would be needed in series. advantage is that noise statistically is reduced by 
factor of about 1.4. formally also applies to drift.


> Gesendet: Montag, 21. Juli 2014 um 20:28 Uhr
> Von: "Bob Smither" 
> An: "Discussion of precise voltage measurement" 
> Betreff: Re: [volt-nuts] Matched resistors
>
> On 07/17/2014 10:26 AM, Randy Evans wrote:
> > Frank,
> >
> > The high cost is my concern, although high performance demands high price
> > typically.  I am trying to double the voltage reference from either an
> > LM399 or LTZ1000, hence the need for precision matched resistors for a x2
> > non-inverting amplifier (using a LT1151 precision op amp).  An alternative
> > I am investigating is using the LTC1043 in a voltage doubling circuit as
> > shown in Linear Technology app note AN 42, page 6, Figure 16.  It states
> > that Vout = 2xVin +/- 5 ppm.  I am less concerned about the absolute
> > accuracy than I am about the long term stability.  I assume that a high
> > quality capacitor is required (low leakage, low ESR, low dielectric
> > absorbtion, etc.) but the circuit does not appear to be dependent on the
> > absolute value of the capacitors.  I'm not sure if the two 1uF caps  need
> > to be matched.  If they do then that would be a show stopper.
> >
> > Does anyone have any experience using the LTC1043 in such a circuit?
> 
> Hi Randy,
> 
> There are some other error sources that might need to be considered when using
> the LTC1043.
> 
> I have not used the LTC1043, but note that on the data sheet there is a small
> charge injection at each of the switch pins. In the multiply by 2 circuit 
> shown
> on the data sheet they are using 1 ufd caps.  Typical charge injection 
> (depends
> on voltage level) is 8 pC. With the 1 ufd caps this is 8 uV.  I assume there 
> is
> some offsetting effect - but this might be a significant contributor to the 5
> ppm error that is mentioned.
> 
> There is also a 6 nA (typical) leakage mentioned.  During the "hold" time (
> about 1 msec) of the output 1 ufd cap this comes to 6 uV.
> 
> Regards,
> Bob Smither
> 
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Re: [volt-nuts] Matched resistors

[acbern]

yes, charge injection is an issue with all these switches and these also vary, 
in other words are somewhat unpredictable. now some of this may be compensated 
by a bigger c, but there are natural limits too. so for a production unit to 
sell, this would probably be a killer, but also for home-use, how do you 
predict the behavior over time?

another option to use if you want to stay away from resistors is the 
pwm-solution as implemented by datron in e.g. their 4910. the pwm signal can 
today of course be done by uCs.


> Gesendet: Montag, 21. Juli 2014 um 22:28 Uhr
> Von: "Bob Smither" 
> An: "Discussion of precise voltage measurement" 
> Betreff: Re: [volt-nuts] Matched resistors
>
> On 07/17/2014 10:26 AM, Randy Evans wrote:
> > Frank,
> >
> > The high cost is my concern, although high performance demands high price
> > typically.  I am trying to double the voltage reference from either an
> > LM399 or LTZ1000, hence the need for precision matched resistors for a x2
> > non-inverting amplifier (using a LT1151 precision op amp).  An alternative
> > I am investigating is using the LTC1043 in a voltage doubling circuit as
> > shown in Linear Technology app note AN 42, page 6, Figure 16.  It states
> > that Vout = 2xVin +/- 5 ppm.  I am less concerned about the absolute
> > accuracy than I am about the long term stability.  I assume that a high
> > quality capacitor is required (low leakage, low ESR, low dielectric
> > absorbtion, etc.) but the circuit does not appear to be dependent on the
> > absolute value of the capacitors.  I'm not sure if the two 1uF caps  need
> > to be matched.  If they do then that would be a show stopper.
> >
> > Does anyone have any experience using the LTC1043 in such a circuit?
> 
> Hi Randy,
> 
> There are some other error sources that might need to be considered when using
> the LTC1043.
> 
> I have not used the LTC1043, but note that on the data sheet there is a small
> charge injection at each of the switch pins. In the multiply by 2 circuit 
> shown
> on the data sheet they are using 1 ufd caps.  Typical charge injection 
> (depends
> on voltage level) is 8 pC. With the 1 ufd caps this is 8 uV.  I assume there 
> is
> some offsetting effect - but this might be a significant contributor to the 5
> ppm error that is mentioned.
> 
> There is also a 6 nA (typical) leakage mentioned.  During the "hold" time (
> about 1 msec) of the output 1 ufd cap this comes to 6 uV.
> 
> Regards,
> Bob Smither
> 
> ___
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and follow the instructions there.

Re: [volt-nuts] Matched resistors

[Bob Smither]

On 07/17/2014 10:26 AM, Randy Evans wrote:
> Frank,
>
> The high cost is my concern, although high performance demands high price
> typically.  I am trying to double the voltage reference from either an
> LM399 or LTZ1000, hence the need for precision matched resistors for a x2
> non-inverting amplifier (using a LT1151 precision op amp).  An alternative
> I am investigating is using the LTC1043 in a voltage doubling circuit as
> shown in Linear Technology app note AN 42, page 6, Figure 16.  It states
> that Vout = 2xVin +/- 5 ppm.  I am less concerned about the absolute
> accuracy than I am about the long term stability.  I assume that a high
> quality capacitor is required (low leakage, low ESR, low dielectric
> absorbtion, etc.) but the circuit does not appear to be dependent on the
> absolute value of the capacitors.  I'm not sure if the two 1uF caps  need
> to be matched.  If they do then that would be a show stopper.
>
> Does anyone have any experience using the LTC1043 in such a circuit?

Hi Randy,

There are some other error sources that might need to be considered when using
the LTC1043.

I have not used the LTC1043, but note that on the data sheet there is a small
charge injection at each of the switch pins. In the multiply by 2 circuit shown
on the data sheet they are using 1 ufd caps.  Typical charge injection (depends
on voltage level) is 8 pC. With the 1 ufd caps this is 8 uV.  I assume there is
some offsetting effect - but this might be a significant contributor to the 5
ppm error that is mentioned.

There is also a 6 nA (typical) leakage mentioned.  During the "hold" time (
about 1 msec) of the output 1 ufd cap this comes to 6 uV.

Regards,
Bob Smither

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

Re: [volt-nuts] Matched resistors

[Randy Evans]

Andreas,

Of course, I would also expect the leakage currents to change over
time/temperature and I would expect them to be the dominant error source.

Randy


On Mon, Jul 21, 2014 at 9:38 AM, Randy Evans 
wrote:

> Andreas,
>
> Since you are familiar with the LTC1043, do you know what stability over
> time and temperature one could expect for the X2 circuit, assuming a high
> quality low leakage capacitor was used?   Since the circuit does not appear
> to be sensitive to the capacitor value, the primary change over time and
> temperature would be expected to be the switch resistance I would think.
>  If the circuit were fed into a high impedance buffer (LTC1151), then I
> would expect the switch resistance to have minimal impact.  What do you
> think?
>
> thanks,
>
> Randy
>
>
> On Sat, Jul 19, 2014 at 8:58 AM, Andreas Jahn 
> wrote:
>
>> Hello Randy,
>>
>> some information you will get on eevblog. (its much easier to post
>> (larger) pictures there).
>> Namely within the LTZ1000, LM399 and T.C. Measurements threads:
>>
>> http://www.eevblog.com/forum/projects/ultra-precision-reference-ltz1000/
>> http://www.eevblog.com/forum/projects/lm399-based-10-v-reference/
>> http://www.eevblog.com/forum/projects/t-c-measurements-on-
>> precision-resistors/
>> http://www.eevblog.com/forum/projects/oshw-24bit-adc-
>> measurement-system-for-voltage-references/
>> http://www.eevblog.com/forum/projects/building-a-7-decade-
>> voltage-calibrator/
>> http://www.eevblog.com/forum/projects/ppmgeek!-5-5-digit-
>> dvm-volt-ref-cal-%28for-arduino-or-any-uc-w-spi%29/msg296127/#msg296127
>>
>> With best regards
>>
>> Andreas
>>
>> Am 19.07.2014 16:33, schrieb Randy Evans:
>>
>>  Andreas,
>>>
>>> Thanks for the information.  Do you have the drift chart, etc. posted
>>> anywhere?  that would be very interesting reading.
>>>
>>> Thanks,
>>>
>>> Randy
>>>
>>>
>>> On Fri, Jul 18, 2014 at 10:11 PM, Andreas Jahn <
>>> andreas_-_j...@t-online.de>
>>> wrote:
>>>
>>>  Hello Randy,

 I think the only difference is in oscillator section (and thus power
 consumption)
 and of cause the TSSOP-package.
 The LTC1043 is easily available from stock e.g. from digikey.
 The LTC6943 is more difficult to get.
 Within the Keithley 2002 LTC1043 is used.
 http://www.eevblog.com/forum/testgear/keithley-2002-8-5-
 digit-dmm-review-and-teardown/
 http://dev.xdevs.com/projects/kei2002/repository/entry/
 photos/K1/small/K2002_1-2251.jpg

 I have added a drift chart with longterm drift data.
 Note: the drift is for the whole measurement arrangement.
 It consists of 3 7V references (2 LTZ1000A and 1 LM399)
 measured via a LTC1043 divider with a 24 bit LTC2400 ADC with
 temperature compensated voltage reference AD586LQ.
 So most of the drift is related to the AD586LQ reference.
 (X-axis is in days, Y-axis in ppm)

 I get around 2 ppm drift for the LTZ1000A  over 1 year
 which I guess is mostly humidity related
 from the ADC printed cirquit board + AD586 reference drift
 and usually below 0.25 ppm standard deviation over 1000 hours.  (42
 days).
 All at unstabilized room temperature.
 I guess with resistors you will need ovenized temperature stabilisation
 to
 achieve this.

 with best regards

 Andreas

 Am 19.07.2014 05:57, schrieb Randy Evans:

   Andreas,

> That is good information, I appreciate it.  I have contacted LT
> application
> support but they have yet to get back to me on my questions except they
> did
> recommend to use the LTC6943 instead of the LTC1043.  Later generation
> I
> guess.
>
> I think i am going to try both the LTC6943 and the LT5400 resistor
> array
> and characterize them.  The LT5400 matching ratio looks pretty good
> over
> temp (0.2ppm/C) but the absolute resistor change over temp is -10 to
> +25
> ppm/C, a little larger than I would like for the circuit I am using.
>
> Randy
>
>
> On Thu, Jul 17, 2014 at 10:37 PM, Andreas Jahn <
> andreas_-_j...@t-online.de>
> wrote:
>
>   Hello Randy,
>
>> I am using the LTC1043 in 1/2 VIN or 1/3 VIN configuration.
>> A matching of the caps is not necessary.
>> In the 1/2 VIN or 1/3 VIN configuration a matching would give
>> the advantage that the settling time of the cirquit is reduced.
>> But in 2* VIN or inverting configuration a matching gives no
>> advantage.
>> So perhaps it is better to put a 1/2 VIN divider into a feedback loop.
>>
>> The most important point: you will need a low leakage buffer
>> amplifier at
>> the output.
>> The caps should be low leakage foil capacitors. (polypropylene would
>> be
>> best).
>> The ESR is negligible against the switch resistance of around 1000
>> Ohms
>> And dielectric absorption would also affect only settling time.
>>
>> In 1/

Re: [volt-nuts] Matched resistors

[Andreas Jahn]

Hello Randy,

I have no experience with a voltage doubler.
From theory the output impedance gets halved by a 2:1 divider
and gets doubled with a X2 multiplier.
So I would expect around a factor 4 more influence of error sources.
But this is only a best guess.

The leakage current of the buffer is usually not the limit.
You have to pay attention on the surface resistance of your PCB
and the leakage of your capacitors.

With best regards

Andreas

Am 21.07.2014 18:38, schrieb Randy Evans:

Andreas,

Since you are familiar with the LTC1043, do you know stability over
time and temperature one could expect for the X2 circuit, assuming a high
quality low leakage capacitor was used?   Since the circuit does not appear
to be sensitive to the capacitor value, the primary change over time and
temperature would be expected to be the switch resistance I would think.
  If the circuit were fed into a high impedance buffer (LTC1151), then I
would expect the switch resistance to have minimal impact.  What do you
think?

thanks,

Randy


On Sat, Jul 19, 2014 at 8:58 AM, Andreas Jahn 
wrote:


Hello Randy,

some information you will get on eevblog. (its much easier to post
(larger) pictures there).
Namely within the LTZ1000, LM399 and T.C. Measurements threads:

http://www.eevblog.com/forum/projects/ultra-precision-reference-ltz1000/
http://www.eevblog.com/forum/projects/lm399-based-10-v-reference/
http://www.eevblog.com/forum/projects/t-c-measurements-on-
precision-resistors/
http://www.eevblog.com/forum/projects/oshw-24bit-adc-
measurement-system-for-voltage-references/
http://www.eevblog.com/forum/projects/building-a-7-decade-
voltage-calibrator/
http://www.eevblog.com/forum/projects/ppmgeek!-5-5-digit-
dvm-volt-ref-cal-%28for-arduino-or-any-uc-w-spi%29/msg296127/#msg296127

With best regards

Andreas

Am 19.07.2014 16:33, schrieb Randy Evans:

  Andreas,

Thanks for the information.  Do you have the drift chart, etc. posted
anywhere?  that would be very interesting reading.

Thanks,

Randy


On Fri, Jul 18, 2014 at 10:11 PM, Andreas Jahn <
andreas_-_j...@t-online.de>
wrote:

  Hello Randy,

I think the only difference is in oscillator section (and thus power
consumption)
and of cause the TSSOP-package.
The LTC1043 is easily available from stock e.g. from digikey.
The LTC6943 is more difficult to get.
Within the Keithley 2002 LTC1043 is used.
http://www.eevblog.com/forum/testgear/keithley-2002-8-5-
digit-dmm-review-and-teardown/
http://dev.xdevs.com/projects/kei2002/repository/entry/
photos/K1/small/K2002_1-2251.jpg

I have added a drift chart with longterm drift data.
Note: the drift is for the whole measurement arrangement.
It consists of 3 7V references (2 LTZ1000A and 1 LM399)
measured via a LTC1043 divider with a 24 bit LTC2400 ADC with
temperature compensated voltage reference AD586LQ.
So most of the drift is related to the AD586LQ reference.
(X-axis is in days, Y-axis in ppm)

I get around 2 ppm drift for the LTZ1000A  over 1 year
which I guess is mostly humidity related
from the ADC printed cirquit board + AD586 reference drift
and usually below 0.25 ppm standard deviation over 1000 hours.  (42
days).
All at unstabilized room temperature.
I guess with resistors you will need ovenized temperature stabilisation
to
achieve this.

with best regards

Andreas

Am 19.07.2014 05:57, schrieb Randy Evans:

   Andreas,


That is good information, I appreciate it.  I have contacted LT
application
support but they have yet to get back to me on my questions except they
did
recommend to use the LTC6943 instead of the LTC1043.  Later generation I
guess.

I think i am going to try both the LTC6943 and the LT5400 resistor array
and characterize them.  The LT5400 matching ratio looks pretty good over
temp (0.2ppm/C) but the absolute resistor change over temp is -10 to +25
ppm/C, a little larger than I would like for the circuit I am using.

Randy


On Thu, Jul 17, 2014 at 10:37 PM, Andreas Jahn <
andreas_-_j...@t-online.de>
wrote:

   Hello Randy,


I am using the LTC1043 in 1/2 VIN or 1/3 VIN configuration.
A matching of the caps is not necessary.
In the 1/2 VIN or 1/3 VIN configuration a matching would give
the advantage that the settling time of the cirquit is reduced.
But in 2* VIN or inverting configuration a matching gives no advantage.
So perhaps it is better to put a 1/2 VIN divider into a feedback loop.

The most important point: you will need a low leakage buffer amplifier
at
the output.
The caps should be low leakage foil capacitors. (polypropylene would be
best).
The ESR is negligible against the switch resistance of around 1000 Ohms
And dielectric absorption would also affect only settling time.

In 1/2 VIN configuration I am using cheap small mylar capacitors (WIMA
MKS02)
(isolation time constant is given only with  >1250 sec (3000 sec typ)).
Buffer amplifier is a LTC1050.
The circuit is very stable over temperature (10 - 40 deg C).
The absolute amplification error is usually some ppm lower than exact
2:1
value.
(dep

Re: [volt-nuts] Matched resistors

[Randy Evans]

Andreas,

Since you are familiar with the LTC1043, do you know what stability over
time and temperature one could expect for the X2 circuit, assuming a high
quality low leakage capacitor was used?   Since the circuit does not appear
to be sensitive to the capacitor value, the primary change over time and
temperature would be expected to be the switch resistance I would think.
 If the circuit were fed into a high impedance buffer (LTC1151), then I
would expect the switch resistance to have minimal impact.  What do you
think?

thanks,

Randy


On Sat, Jul 19, 2014 at 8:58 AM, Andreas Jahn 
wrote:

> Hello Randy,
>
> some information you will get on eevblog. (its much easier to post
> (larger) pictures there).
> Namely within the LTZ1000, LM399 and T.C. Measurements threads:
>
> http://www.eevblog.com/forum/projects/ultra-precision-reference-ltz1000/
> http://www.eevblog.com/forum/projects/lm399-based-10-v-reference/
> http://www.eevblog.com/forum/projects/t-c-measurements-on-
> precision-resistors/
> http://www.eevblog.com/forum/projects/oshw-24bit-adc-
> measurement-system-for-voltage-references/
> http://www.eevblog.com/forum/projects/building-a-7-decade-
> voltage-calibrator/
> http://www.eevblog.com/forum/projects/ppmgeek!-5-5-digit-
> dvm-volt-ref-cal-%28for-arduino-or-any-uc-w-spi%29/msg296127/#msg296127
>
> With best regards
>
> Andreas
>
> Am 19.07.2014 16:33, schrieb Randy Evans:
>
>  Andreas,
>>
>> Thanks for the information.  Do you have the drift chart, etc. posted
>> anywhere?  that would be very interesting reading.
>>
>> Thanks,
>>
>> Randy
>>
>>
>> On Fri, Jul 18, 2014 at 10:11 PM, Andreas Jahn <
>> andreas_-_j...@t-online.de>
>> wrote:
>>
>>  Hello Randy,
>>>
>>> I think the only difference is in oscillator section (and thus power
>>> consumption)
>>> and of cause the TSSOP-package.
>>> The LTC1043 is easily available from stock e.g. from digikey.
>>> The LTC6943 is more difficult to get.
>>> Within the Keithley 2002 LTC1043 is used.
>>> http://www.eevblog.com/forum/testgear/keithley-2002-8-5-
>>> digit-dmm-review-and-teardown/
>>> http://dev.xdevs.com/projects/kei2002/repository/entry/
>>> photos/K1/small/K2002_1-2251.jpg
>>>
>>> I have added a drift chart with longterm drift data.
>>> Note: the drift is for the whole measurement arrangement.
>>> It consists of 3 7V references (2 LTZ1000A and 1 LM399)
>>> measured via a LTC1043 divider with a 24 bit LTC2400 ADC with
>>> temperature compensated voltage reference AD586LQ.
>>> So most of the drift is related to the AD586LQ reference.
>>> (X-axis is in days, Y-axis in ppm)
>>>
>>> I get around 2 ppm drift for the LTZ1000A  over 1 year
>>> which I guess is mostly humidity related
>>> from the ADC printed cirquit board + AD586 reference drift
>>> and usually below 0.25 ppm standard deviation over 1000 hours.  (42
>>> days).
>>> All at unstabilized room temperature.
>>> I guess with resistors you will need ovenized temperature stabilisation
>>> to
>>> achieve this.
>>>
>>> with best regards
>>>
>>> Andreas
>>>
>>> Am 19.07.2014 05:57, schrieb Randy Evans:
>>>
>>>   Andreas,
>>>
 That is good information, I appreciate it.  I have contacted LT
 application
 support but they have yet to get back to me on my questions except they
 did
 recommend to use the LTC6943 instead of the LTC1043.  Later generation I
 guess.

 I think i am going to try both the LTC6943 and the LT5400 resistor array
 and characterize them.  The LT5400 matching ratio looks pretty good over
 temp (0.2ppm/C) but the absolute resistor change over temp is -10 to +25
 ppm/C, a little larger than I would like for the circuit I am using.

 Randy


 On Thu, Jul 17, 2014 at 10:37 PM, Andreas Jahn <
 andreas_-_j...@t-online.de>
 wrote:

   Hello Randy,

> I am using the LTC1043 in 1/2 VIN or 1/3 VIN configuration.
> A matching of the caps is not necessary.
> In the 1/2 VIN or 1/3 VIN configuration a matching would give
> the advantage that the settling time of the cirquit is reduced.
> But in 2* VIN or inverting configuration a matching gives no advantage.
> So perhaps it is better to put a 1/2 VIN divider into a feedback loop.
>
> The most important point: you will need a low leakage buffer amplifier
> at
> the output.
> The caps should be low leakage foil capacitors. (polypropylene would be
> best).
> The ESR is negligible against the switch resistance of around 1000 Ohms
> And dielectric absorption would also affect only settling time.
>
> In 1/2 VIN configuration I am using cheap small mylar capacitors (WIMA
> MKS02)
> (isolation time constant is given only with  >1250 sec (3000 sec typ)).
> Buffer amplifier is a LTC1050.
> The circuit is very stable over temperature (10 - 40 deg C).
> The absolute amplification error is usually some ppm lower than exact
> 2:1
> value.
> (depends somewhat on the pinning which

Re: [volt-nuts] Matched resistors

[Andreas Jahn]

Hello Randy,

some information you will get on eevblog. (its much easier to post 
(larger) pictures there).

Namely within the LTZ1000, LM399 and T.C. Measurements threads:

http://www.eevblog.com/forum/projects/ultra-precision-reference-ltz1000/
http://www.eevblog.com/forum/projects/lm399-based-10-v-reference/
http://www.eevblog.com/forum/projects/t-c-measurements-on-precision-resistors/
http://www.eevblog.com/forum/projects/oshw-24bit-adc-measurement-system-for-voltage-references/
http://www.eevblog.com/forum/projects/building-a-7-decade-voltage-calibrator/
http://www.eevblog.com/forum/projects/ppmgeek!-5-5-digit-dvm-volt-ref-cal-%28for-arduino-or-any-uc-w-spi%29/msg296127/#msg296127

With best regards

Andreas

Am 19.07.2014 16:33, schrieb Randy Evans:

Andreas,

Thanks for the information.  Do you have the drift chart, etc. posted
anywhere?  that would be very interesting reading.

Thanks,

Randy


On Fri, Jul 18, 2014 at 10:11 PM, Andreas Jahn 
wrote:


Hello Randy,

I think the only difference is in oscillator section (and thus power
consumption)
and of cause the TSSOP-package.
The LTC1043 is easily available from stock e.g. from digikey.
The LTC6943 is more difficult to get.
Within the Keithley 2002 LTC1043 is used.
http://www.eevblog.com/forum/testgear/keithley-2002-8-5-
digit-dmm-review-and-teardown/
http://dev.xdevs.com/projects/kei2002/repository/entry/
photos/K1/small/K2002_1-2251.jpg

I have added a drift chart with longterm drift data.
Note: the drift is for the whole measurement arrangement.
It consists of 3 7V references (2 LTZ1000A and 1 LM399)
measured via a LTC1043 divider with a 24 bit LTC2400 ADC with
temperature compensated voltage reference AD586LQ.
So most of the drift is related to the AD586LQ reference.
(X-axis is in days, Y-axis in ppm)

I get around 2 ppm drift for the LTZ1000A  over 1 year
which I guess is mostly humidity related
from the ADC printed cirquit board + AD586 reference drift
and usually below 0.25 ppm standard deviation over 1000 hours.  (42 days).
All at unstabilized room temperature.
I guess with resistors you will need ovenized temperature stabilisation to
achieve this.

with best regards

Andreas

Am 19.07.2014 05:57, schrieb Randy Evans:

  Andreas,

That is good information, I appreciate it.  I have contacted LT
application
support but they have yet to get back to me on my questions except they
did
recommend to use the LTC6943 instead of the LTC1043.  Later generation I
guess.

I think i am going to try both the LTC6943 and the LT5400 resistor array
and characterize them.  The LT5400 matching ratio looks pretty good over
temp (0.2ppm/C) but the absolute resistor change over temp is -10 to +25
ppm/C, a little larger than I would like for the circuit I am using.

Randy


On Thu, Jul 17, 2014 at 10:37 PM, Andreas Jahn <
andreas_-_j...@t-online.de>
wrote:

  Hello Randy,

I am using the LTC1043 in 1/2 VIN or 1/3 VIN configuration.
A matching of the caps is not necessary.
In the 1/2 VIN or 1/3 VIN configuration a matching would give
the advantage that the settling time of the cirquit is reduced.
But in 2* VIN or inverting configuration a matching gives no advantage.
So perhaps it is better to put a 1/2 VIN divider into a feedback loop.

The most important point: you will need a low leakage buffer amplifier at
the output.
The caps should be low leakage foil capacitors. (polypropylene would be
best).
The ESR is negligible against the switch resistance of around 1000 Ohms
And dielectric absorption would also affect only settling time.

In 1/2 VIN configuration I am using cheap small mylar capacitors (WIMA
MKS02)
(isolation time constant is given only with  >1250 sec (3000 sec typ)).
Buffer amplifier is a LTC1050.
The circuit is very stable over temperature (10 - 40 deg C).
The absolute amplification error is usually some ppm lower than exact 2:1
value.
(depends somewhat on the pinning which is used so I am not shure wether
the pins are mixed up regarding the charge compensation)

So I dont know wether the ±1 ppm is more a stability figure than a
absolute value.
Even polypropylene capacitors do not change the amplification error.

With best regards

Andreas

Am 17.07.2014 17:26, schrieb Randy Evans:

  Frank,

The high cost is my concern, although high performance demands high
price
typically.  I am trying to double the voltage reference from either an
LM399 or LTZ1000, hence the need for precision matched resistors for a
x2
non-inverting amplifier (using a LT1151 precision op amp).  An
alternative
I am investigating is using the LTC1043 in a voltage doubling circuit as
shown in Linear Technology app note AN 42, page 6, Figure 16.  It states
that Vout = 2xVin ± 5 ppm.  I am less concerned about the absolute

accuracy than I am about the long term stability.  I assume that a high
quality capacitor is required (low leakage, low ESR, low dielectric
absorbtion, etc.) but the circuit does not appear to be dependent on the
absolute value of the capacitors.  I'm not sure if

Re: [volt-nuts] Matched resistors

[Randy Evans]

Andreas,

Thanks for the information.  Do you have the drift chart, etc. posted
anywhere?  that would be very interesting reading.

Thanks,

Randy


On Fri, Jul 18, 2014 at 10:11 PM, Andreas Jahn 
wrote:

> Hello Randy,
>
> I think the only difference is in oscillator section (and thus power
> consumption)
> and of cause the TSSOP-package.
> The LTC1043 is easily available from stock e.g. from digikey.
> The LTC6943 is more difficult to get.
> Within the Keithley 2002 LTC1043 is used.
> http://www.eevblog.com/forum/testgear/keithley-2002-8-5-
> digit-dmm-review-and-teardown/
> http://dev.xdevs.com/projects/kei2002/repository/entry/
> photos/K1/small/K2002_1-2251.jpg
>
> I have added a drift chart with longterm drift data.
> Note: the drift is for the whole measurement arrangement.
> It consists of 3 7V references (2 LTZ1000A and 1 LM399)
> measured via a LTC1043 divider with a 24 bit LTC2400 ADC with
> temperature compensated voltage reference AD586LQ.
> So most of the drift is related to the AD586LQ reference.
> (X-axis is in days, Y-axis in ppm)
>
> I get around 2 ppm drift for the LTZ1000A  over 1 year
> which I guess is mostly humidity related
> from the ADC printed cirquit board + AD586 reference drift
> and usually below 0.25 ppm standard deviation over 1000 hours.  (42 days).
> All at unstabilized room temperature.
> I guess with resistors you will need ovenized temperature stabilisation to
> achieve this.
>
> with best regards
>
> Andreas
>
> Am 19.07.2014 05:57, schrieb Randy Evans:
>
>  Andreas,
>>
>> That is good information, I appreciate it.  I have contacted LT
>> application
>> support but they have yet to get back to me on my questions except they
>> did
>> recommend to use the LTC6943 instead of the LTC1043.  Later generation I
>> guess.
>>
>> I think i am going to try both the LTC6943 and the LT5400 resistor array
>> and characterize them.  The LT5400 matching ratio looks pretty good over
>> temp (0.2ppm/C) but the absolute resistor change over temp is -10 to +25
>> ppm/C, a little larger than I would like for the circuit I am using.
>>
>> Randy
>>
>>
>> On Thu, Jul 17, 2014 at 10:37 PM, Andreas Jahn <
>> andreas_-_j...@t-online.de>
>> wrote:
>>
>>  Hello Randy,
>>>
>>> I am using the LTC1043 in 1/2 VIN or 1/3 VIN configuration.
>>> A matching of the caps is not necessary.
>>> In the 1/2 VIN or 1/3 VIN configuration a matching would give
>>> the advantage that the settling time of the cirquit is reduced.
>>> But in 2* VIN or inverting configuration a matching gives no advantage.
>>> So perhaps it is better to put a 1/2 VIN divider into a feedback loop.
>>>
>>> The most important point: you will need a low leakage buffer amplifier at
>>> the output.
>>> The caps should be low leakage foil capacitors. (polypropylene would be
>>> best).
>>> The ESR is negligible against the switch resistance of around 1000 Ohms
>>> And dielectric absorption would also affect only settling time.
>>>
>>> In 1/2 VIN configuration I am using cheap small mylar capacitors (WIMA
>>> MKS02)
>>> (isolation time constant is given only with  >1250 sec (3000 sec typ)).
>>> Buffer amplifier is a LTC1050.
>>> The circuit is very stable over temperature (10 - 40 deg C).
>>> The absolute amplification error is usually some ppm lower than exact 2:1
>>> value.
>>> (depends somewhat on the pinning which is used so I am not shure wether
>>> the pins are mixed up regarding the charge compensation)
>>>
>>> So I dont know wether the ±1 ppm is more a stability figure than a
>>> absolute value.
>>> Even polypropylene capacitors do not change the amplification error.
>>>
>>> With best regards
>>>
>>> Andreas
>>>
>>> Am 17.07.2014 17:26, schrieb Randy Evans:
>>>
>>>  Frank,

 The high cost is my concern, although high performance demands high
 price
 typically.  I am trying to double the voltage reference from either an
 LM399 or LTZ1000, hence the need for precision matched resistors for a
 x2
 non-inverting amplifier (using a LT1151 precision op amp).  An
 alternative
 I am investigating is using the LTC1043 in a voltage doubling circuit as
 shown in Linear Technology app note AN 42, page 6, Figure 16.  It states
 that Vout = 2xVin ± 5 ppm.  I am less concerned about the absolute

 accuracy than I am about the long term stability.  I assume that a high
 quality capacitor is required (low leakage, low ESR, low dielectric
 absorbtion, etc.) but the circuit does not appear to be dependent on the
 absolute value of the capacitors.  I'm not sure if the two 1uF caps
  need
 to be matched.  If they do then that would be a show stopper.

 Does anyone have any experience using the LTC1043 in such a circuit?

 Thanks,

 Randy

   ___

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>>> mailman/listinfo/volt-nuts
>>> and follow the instruc

Re: [volt-nuts] Matched resistors

[Andreas Jahn]

http://www.vishaypg.com/foil-resistors/list/product-63036/
http://www.vishaypg.com/doc?63036

Am 19.07.2014 06:07, schrieb Randy Evans:

I figured out that VPG is Vishay Precision Group but I have not managed to
identify the vhd hermetic divider.  Could you point me to the location on
the Vishay web site?

Thanks,

Randy


On Fri, Jul 18, 2014 at 9:00 PM, Randy Evans 
wrote:


I am not familiar with "vpg" or "vhd" terms.  I assume the former is a
company (European?) and the latter is a model type?  Do you have a URL or
other information to get followup information.  The 0.1 ppm tracking is
exactly what I am looking for and I don't need absolute accuracy.

Thanks,

Randy


On Fri, Jul 18, 2014 at 12:00 AM,  wrote:


randy,
re. vpg: they offer an hermetic divider (vhd) with typ. 0.1ppm tracking
of tempco. if you are ok with lowest available abs. accuracy it will be
well priced, I remember having asked them for a price and it was below 50€
for standard lead time (which can be very long). it is also fair to assume
it would age more homogeneously than two separate resistors, also you dont
need to think about how to keep two resistors at the same temp. make sure
each resistor is loaded with less than 10mw, otherwise aging may be above
what the claim in their collateral.




Gesendet: Donnerstag, 17. Juli 2014 um 04:40 Uhr
Von: "Frank Stellmach" 
An: volt-nuts@febo.com
Betreff: [volt-nuts] Matched resistors

Randy,

resistor matched in T.C. are extremely expensive, as the manufacturer
(or yourself) would have to select these from a batch of many samples.

reistors with very small T.C. (<1ppm/K) would do the job also, but they
also need to be stable over time, in shelf life opereation mode, i.e.
P<10mW.

That means, you need those hermetically sealed VHP202Z from Vishay, T.C.
is typically < 1ppm/K and they are stable to < 2ppm over 5years. But
they cost already 80€ each, depending on tolerance.

I made a longterm observation of these and found these parameters

confirmed.

Frank
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Re: [volt-nuts] Matched resistors

[Randy Evans]

I figured out that VPG is Vishay Precision Group but I have not managed to
identify the vhd hermetic divider.  Could you point me to the location on
the Vishay web site?

Thanks,

Randy


On Fri, Jul 18, 2014 at 9:00 PM, Randy Evans 
wrote:

> I am not familiar with "vpg" or "vhd" terms.  I assume the former is a
> company (European?) and the latter is a model type?  Do you have a URL or
> other information to get followup information.  The 0.1 ppm tracking is
> exactly what I am looking for and I don't need absolute accuracy.
>
> Thanks,
>
> Randy
>
>
> On Fri, Jul 18, 2014 at 12:00 AM,  wrote:
>
>> randy,
>> re. vpg: they offer an hermetic divider (vhd) with typ. 0.1ppm tracking
>> of tempco. if you are ok with lowest available abs. accuracy it will be
>> well priced, I remember having asked them for a price and it was below 50€
>> for standard lead time (which can be very long). it is also fair to assume
>> it would age more homogeneously than two separate resistors, also you dont
>> need to think about how to keep two resistors at the same temp. make sure
>> each resistor is loaded with less than 10mw, otherwise aging may be above
>> what the claim in their collateral.
>>
>>
>>
>> > Gesendet: Donnerstag, 17. Juli 2014 um 04:40 Uhr
>> > Von: "Frank Stellmach" 
>> > An: volt-nuts@febo.com
>> > Betreff: [volt-nuts] Matched resistors
>> >
>> > Randy,
>> >
>> > resistor matched in T.C. are extremely expensive, as the manufacturer
>> > (or yourself) would have to select these from a batch of many samples.
>> >
>> > reistors with very small T.C. (<1ppm/K) would do the job also, but they
>> > also need to be stable over time, in shelf life opereation mode, i.e.
>> > P<10mW.
>> >
>> > That means, you need those hermetically sealed VHP202Z from Vishay, T.C.
>> > is typically < 1ppm/K and they are stable to < 2ppm over 5years. But
>> > they cost already 80€ each, depending on tolerance.
>> >
>> > I made a longterm observation of these and found these parameters
>> confirmed.
>> >
>> > Frank
>> > ___
>> > 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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>> To unsubscribe, go to
>> https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
>> and follow the instructions there.
>>
>
>
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Re: [volt-nuts] Matched resistors

[Randy Evans]

I am not familiar with "vpg" or "vhd" terms.  I assume the former is a
company (European?) and the latter is a model type?  Do you have a URL or
other information to get followup information.  The 0.1 ppm tracking is
exactly what I am looking for and I don't need absolute accuracy.

Thanks,

Randy


On Fri, Jul 18, 2014 at 12:00 AM,  wrote:

> randy,
> re. vpg: they offer an hermetic divider (vhd) with typ. 0.1ppm tracking of
> tempco. if you are ok with lowest available abs. accuracy it will be well
> priced, I remember having asked them for a price and it was below 50€ for
> standard lead time (which can be very long). it is also fair to assume it
> would age more homogeneously than two separate resistors, also you dont
> need to think about how to keep two resistors at the same temp. make sure
> each resistor is loaded with less than 10mw, otherwise aging may be above
> what the claim in their collateral.
>
>
>
> > Gesendet: Donnerstag, 17. Juli 2014 um 04:40 Uhr
> > Von: "Frank Stellmach" 
> > An: volt-nuts@febo.com
> > Betreff: [volt-nuts] Matched resistors
> >
> > Randy,
> >
> > resistor matched in T.C. are extremely expensive, as the manufacturer
> > (or yourself) would have to select these from a batch of many samples.
> >
> > reistors with very small T.C. (<1ppm/K) would do the job also, but they
> > also need to be stable over time, in shelf life opereation mode, i.e.
> > P<10mW.
> >
> > That means, you need those hermetically sealed VHP202Z from Vishay, T.C.
> > is typically < 1ppm/K and they are stable to < 2ppm over 5years. But
> > they cost already 80€ each, depending on tolerance.
> >
> > I made a longterm observation of these and found these parameters
> confirmed.
> >
> > Frank
> > ___
> > 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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> https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
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>
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Re: [volt-nuts] Matched resistors

[Randy Evans]

Andreas,

That is good information, I appreciate it.  I have contacted LT application
support but they have yet to get back to me on my questions except they did
recommend to use the LTC6943 instead of the LTC1043.  Later generation I
guess.

I think i am going to try both the LTC6943 and the LT5400 resistor array
and characterize them.  The LT5400 matching ratio looks pretty good over
temp (0.2ppm/C) but the absolute resistor change over temp is -10 to +25
ppm/C, a little larger than I would like for the circuit I am using.

Randy


On Thu, Jul 17, 2014 at 10:37 PM, Andreas Jahn 
wrote:

> Hello Randy,
>
> I am using the LTC1043 in 1/2 VIN or 1/3 VIN configuration.
> A matching of the caps is not necessary.
> In the 1/2 VIN or 1/3 VIN configuration a matching would give
> the advantage that the settling time of the cirquit is reduced.
> But in 2* VIN or inverting configuration a matching gives no advantage.
> So perhaps it is better to put a 1/2 VIN divider into a feedback loop.
>
> The most important point: you will need a low leakage buffer amplifier at
> the output.
> The caps should be low leakage foil capacitors. (polypropylene would be
> best).
> The ESR is negligible against the switch resistance of around 1000 Ohms
> And dielectric absorption would also affect only settling time.
>
> In 1/2 VIN configuration I am using cheap small mylar capacitors (WIMA
> MKS02)
> (isolation time constant is given only with  >1250 sec (3000 sec typ)).
> Buffer amplifier is a LTC1050.
> The circuit is very stable over temperature (10 - 40 deg C).
> The absolute amplification error is usually some ppm lower than exact 2:1
> value.
> (depends somewhat on the pinning which is used so I am not shure wether
> the pins are mixed up regarding the charge compensation)
>
> So I dont know wether the ±1 ppm is more a stability figure than a
> absolute value.
> Even polypropylene capacitors do not change the amplification error.
>
> With best regards
>
> Andreas
>
> Am 17.07.2014 17:26, schrieb Randy Evans:
>
>> Frank,
>>
>> The high cost is my concern, although high performance demands high price
>> typically.  I am trying to double the voltage reference from either an
>> LM399 or LTZ1000, hence the need for precision matched resistors for a x2
>> non-inverting amplifier (using a LT1151 precision op amp).  An alternative
>> I am investigating is using the LTC1043 in a voltage doubling circuit as
>> shown in Linear Technology app note AN 42, page 6, Figure 16.  It states
>> that Vout = 2xVin ± 5 ppm.  I am less concerned about the absolute
>>
>> accuracy than I am about the long term stability.  I assume that a high
>> quality capacitor is required (low leakage, low ESR, low dielectric
>> absorbtion, etc.) but the circuit does not appear to be dependent on the
>> absolute value of the capacitors.  I'm not sure if the two 1uF caps  need
>> to be matched.  If they do then that would be a show stopper.
>>
>> Does anyone have any experience using the LTC1043 in such a circuit?
>>
>> Thanks,
>>
>> Randy
>>
>>  ___
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Re: [volt-nuts] Matched resistors

[acbern]

randy, 
re. vpg: they offer an hermetic divider (vhd) with typ. 0.1ppm tracking of 
tempco. if you are ok with lowest available abs. accuracy it will be well 
priced, I remember having asked them for a price and it was below 50€ for 
standard lead time (which can be very long). it is also fair to assume it would 
age more homogeneously than two separate resistors, also you dont need to think 
about how to keep two resistors at the same temp. make sure each resistor is 
loaded with less than 10mw, otherwise aging may be above what the claim in 
their collateral. 



> Gesendet: Donnerstag, 17. Juli 2014 um 04:40 Uhr
> Von: "Frank Stellmach" 
> An: volt-nuts@febo.com
> Betreff: [volt-nuts] Matched resistors
>
> Randy,
> 
> resistor matched in T.C. are extremely expensive, as the manufacturer 
> (or yourself) would have to select these from a batch of many samples.
> 
> reistors with very small T.C. (<1ppm/K) would do the job also, but they 
> also need to be stable over time, in shelf life opereation mode, i.e. 
> P<10mW.
> 
> That means, you need those hermetically sealed VHP202Z from Vishay, T.C. 
> is typically < 1ppm/K and they are stable to < 2ppm over 5years. But 
> they cost already 80€ each, depending on tolerance.
> 
> I made a longterm observation of these and found these parameters confirmed.
> 
> Frank
> ___
> 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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Re: [volt-nuts] Matched resistors

[Andreas Jahn]

Hello Randy,

I am using the LTC1043 in 1/2 VIN or 1/3 VIN configuration.
A matching of the caps is not necessary.
In the 1/2 VIN or 1/3 VIN configuration a matching would give
the advantage that the settling time of the cirquit is reduced.
But in 2* VIN or inverting configuration a matching gives no advantage.
So perhaps it is better to put a 1/2 VIN divider into a feedback loop.

The most important point: you will need a low leakage buffer amplifier 
at the output.
The caps should be low leakage foil capacitors. (polypropylene would be 
best).

The ESR is negligible against the switch resistance of around 1000 Ohms
And dielectric absorption would also affect only settling time.

In 1/2 VIN configuration I am using cheap small mylar capacitors (WIMA 
MKS02)

(isolation time constant is given only with  >1250 sec (3000 sec typ)).
Buffer amplifier is a LTC1050.
The circuit is very stable over temperature (10 - 40 deg C).
The absolute amplification error is usually some ppm lower than exact 
2:1 value.

(depends somewhat on the pinning which is used so I am not shure wether
the pins are mixed up regarding the charge compensation)

So I dont know wether the ±1 ppm is more a stability figure than a 
absolute value.

Even polypropylene capacitors do not change the amplification error.

With best regards

Andreas

Am 17.07.2014 17:26, schrieb Randy Evans:

Frank,

The high cost is my concern, although high performance demands high price
typically.  I am trying to double the voltage reference from either an
LM399 or LTZ1000, hence the need for precision matched resistors for a x2
non-inverting amplifier (using a LT1151 precision op amp).  An 
alternative

I am investigating is using the LTC1043 in a voltage doubling circuit as
shown in Linear Technology app note AN 42, page 6, Figure 16.  It states
that Vout = 2xVin ± 5 ppm.  I am less concerned about the absolute
accuracy than I am about the long term stability.  I assume that a high
quality capacitor is required (low leakage, low ESR, low dielectric
absorbtion, etc.) but the circuit does not appear to be dependent on the
absolute value of the capacitors.  I'm not sure if the two 1uF caps  need
to be matched.  If they do then that would be a show stopper.

Does anyone have any experience using the LTC1043 in such a circuit?

Thanks,

Randy


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Re: [volt-nuts] Matched resistors

[Todd Micallef]

I am not sure if Fluke had matched tempco spare parts, but you can look at
some NOS resistors from Fluke on ebay. They may be a good start and some of
the pricing isn't bad.

Todd


On Thursday, July 17, 2014, Randy Evans wrote:

> Frank,
>
> The high cost is my concern, although high performance demands high price
> typically.  I am trying to double the voltage reference from either an
> LM399 or LTZ1000, hence the need for precision matched resistors for a x2
> non-inverting amplifier (using a LT1151 precision op amp).  An alternative
> I am investigating is using the LTC1043 in a voltage doubling circuit as
> shown in Linear Technology app note AN 42, page 6, Figure 16.  It states
> that Vout = 2xVin +/- 5 ppm.  I am less concerned about the absolute
> accuracy than I am about the long term stability.  I assume that a high
> quality capacitor is required (low leakage, low ESR, low dielectric
> absorbtion, etc.) but the circuit does not appear to be dependent on the
> absolute value of the capacitors.  I'm not sure if the two 1uF caps  need
> to be matched.  If they do then that would be a show stopper.
>
> Does anyone have any experience using the LTC1043 in such a circuit?
>
> Thanks,
>
> Randy
>
>
> On Wed, Jul 16, 2014 at 9:40 PM, Frank Stellmach <
> frank.stellm...@freenet.de 
> > wrote:
>
> > Randy,
> >
> > resistor matched in T.C. are extremely expensive, as the manufacturer (or
> > yourself) would have to select these from a batch of many samples.
> >
> > reistors with very small T.C. (<1ppm/K) would do the job also, but they
> > also need to be stable over time, in shelf life opereation mode, i.e.
> > P<10mW.
> >
> > That means, you need those hermetically sealed VHP202Z from Vishay, T.C.
> > is typically < 1ppm/K and they are stable to < 2ppm over 5years. But they
> > cost already 80€ each, depending on tolerance.
> >
> > I made a longterm observation of these and found these parameters
> > confirmed.
> >
> > Frank
> > ___
> > 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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> To unsubscribe, go to
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Re: [volt-nuts] Matched resistors

[Randy Evans]

Frank,

The high cost is my concern, although high performance demands high price
typically.  I am trying to double the voltage reference from either an
LM399 or LTZ1000, hence the need for precision matched resistors for a x2
non-inverting amplifier (using a LT1151 precision op amp).  An alternative
I am investigating is using the LTC1043 in a voltage doubling circuit as
shown in Linear Technology app note AN 42, page 6, Figure 16.  It states
that Vout = 2xVin +/- 5 ppm.  I am less concerned about the absolute
accuracy than I am about the long term stability.  I assume that a high
quality capacitor is required (low leakage, low ESR, low dielectric
absorbtion, etc.) but the circuit does not appear to be dependent on the
absolute value of the capacitors.  I'm not sure if the two 1uF caps  need
to be matched.  If they do then that would be a show stopper.

Does anyone have any experience using the LTC1043 in such a circuit?

Thanks,

Randy


On Wed, Jul 16, 2014 at 9:40 PM, Frank Stellmach  wrote:

> Randy,
>
> resistor matched in T.C. are extremely expensive, as the manufacturer (or
> yourself) would have to select these from a batch of many samples.
>
> reistors with very small T.C. (<1ppm/K) would do the job also, but they
> also need to be stable over time, in shelf life opereation mode, i.e.
> P<10mW.
>
> That means, you need those hermetically sealed VHP202Z from Vishay, T.C.
> is typically < 1ppm/K and they are stable to < 2ppm over 5years. But they
> cost already 80€ each, depending on tolerance.
>
> I made a longterm observation of these and found these parameters
> confirmed.
>
> Frank
> ___
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> To unsubscribe, go to https://www.febo.com/cgi-bin/
> mailman/listinfo/volt-nuts
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[volt-nuts] Matched resistors

[Frank Stellmach]

Randy,

resistor matched in T.C. are extremely expensive, as the manufacturer 
(or yourself) would have to select these from a batch of many samples.


reistors with very small T.C. (<1ppm/K) would do the job also, but they 
also need to be stable over time, in shelf life opereation mode, i.e. 
P<10mW.


That means, you need those hermetically sealed VHP202Z from Vishay, T.C. 
is typically < 1ppm/K and they are stable to < 2ppm over 5years. But 
they cost already 80€ each, depending on tolerance.


I made a longterm observation of these and found these parameters confirmed.

Frank
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Re: [volt-nuts] Matched resistors

[Tom Knox]

Hi Randy;
I would look at Visha Foil resistors
http://www.vishaypg.com/docs/63120/hzseries.pdf
Hope that helps.
Cheers;
Thomas Knox



> Date: Wed, 16 Jul 2014 17:44:10 -0700
> From: randyevans2...@gmail.com
> To: volt-nuts@febo.com
> Subject: [volt-nuts] Matched resistors
> 
> I am building a 10V voltage reference based on the LTZ1000 and the design
> is essentially done but I am looking for a pair of matched resistors that
> track very closely over temperature.  The absolute value of the pair is not
> important, anything between 50K and 200K ohms would be ideal, but the
> matching ratio is very important.
> 
>  I looked at the 100K ohm LT5400 quad resistor array from Linear Technology
> but it has a worst case long term accelerated shelf life spec of 10 ppm (at
> 150C) matching ratio and long term matching ratio drift of <4ppm (at 70C).
>  I would like something much tighter if possible since that would mean I
> likely don't need an oven for a couple of ppm worst case accuracy over time
> and temperature.  I can make the LT5400 work but I would need to do
> temperature characterization and circuit compensation.  Doable but
> undesirable.
> 
> Does anyone have any ideas for a good ratio matched resistor pair,
> hopefully not too expensive?
> 
> Thanks,
> 
> Randy Evans
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[volt-nuts] Matched resistors

[Randy Evans]

I am building a 10V voltage reference based on the LTZ1000 and the design
is essentially done but I am looking for a pair of matched resistors that
track very closely over temperature.  The absolute value of the pair is not
important, anything between 50K and 200K ohms would be ideal, but the
matching ratio is very important.

 I looked at the 100K ohm LT5400 quad resistor array from Linear Technology
but it has a worst case long term accelerated shelf life spec of 10 ppm (at
150C) matching ratio and long term matching ratio drift of <4ppm (at 70C).
 I would like something much tighter if possible since that would mean I
likely don't need an oven for a couple of ppm worst case accuracy over time
and temperature.  I can make the LT5400 work but I would need to do
temperature characterization and circuit compensation.  Doable but
undesirable.

Does anyone have any ideas for a good ratio matched resistor pair,
hopefully not too expensive?

Thanks,

Randy Evans
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