T.C. measurements on precision resistors

[Dr. Frank]

after several months now I have found one "typical" (= golden) Z201#6 resistor. (Date code B1305-)

So, how many of these expensive foil resistors do I have to buy to find one that has "typical" performance of 0.05ppm/K ?

Easy, that's all about Normal Gauss Distribution, I think?

Frank

[EEVblog]

Look what just turned up:



My 34470A is currently saying it is 10.000200

[babysitter]

Nice!

You should get two additional drills in the enclosure and put a characterised Thermistor inside! Thats how Dr. Frank does it to get to know the temperature of the resistor element.

Fun fact: If I google for Wekomm engineering GmbH, the residues of their incomplete website show they are active in both areas, Metrology and model trains... wonder what that means?

[3roomlab]

Look what just turned up:

My 34470A is currently saying it is 10.000200

just curious, how much (ballpark) does it costs?

[Andreas]

Hello,

more interesting would be if there are any accuracy specs for the values in the datasheet.
(including ageing)
The absolute value seems to be that what they have read from the 3458A multimeter.

For the T.C. it would be interesting over which temperature range did they get the coefficients.

A teardown with photos would be nice. (if the resistor is hermetically sealed).

With best regards

Andreas

[Dr. Frank]

Look what just turned up:
..

My 34470A is currently saying it is 10.000200

Hi Dave,

looks really solid, but it lacks a thermometer for that uncertainty grade..

Although 28ppm deviation is within specification of the 33470A...

Did you correct for ambient temperature, and did you use 4W and offset compensation?

Would also like to see the inner construction.

Frank

[Dr. Frank]

Hello,

more interesting would be if there are any accuracy specs for the values in the datasheet.
(including ageing)
The absolute value seems to be that what they have read from the 3458A multimeter.

...
With best regards

Andreas

The 3458A delivers 7 decimal places only.
Maybe they use another 8 1/2 digit DMM, or more probably, a precision resistance bridge with another reference resistor.

Frank

[Andreas]

The 3458A delivers 7 decimal places only.

Even if I use the HPIB connection?
The 28 Bit converter should give a total of 8 digits.

With best regards

Andreas

[Dr. Frank]

The 3458A delivers 7 decimal places only.

Even if I use the HPIB connection?
The 28 Bit converter should give a total of 8 digits.

With best regards

Andreas

For the 3458A (and also all other 8.5 DMMs) the 8th digit is meaningless.
Transfer accuracy, i.e. comparison to another external reference resistor really is 0.2ppm at best, and absolute uncertainty of the internal references is about 2ppm/24h.

Therefore, if they write 8 digits on their box, they either must have used something else, an ESI SR104, or maybe measured at PTB (what I doubt w/o a thermometer inside), or they are not very serious.

Btw.: Their homepage is not working, I can't access their metrology site and can't retrieve the spec.

Frank

[ManateeMafia]

Measurements International has the following brochure...

http://www.mintl.com/media/pdfs/accubridge.pdf

Does this mean all the extra digits (10's of ppb) are meaningless or do they have a useful application?

I have not seen any videos of these in operation so I am guessing they are not as easy to operate as their sales people advertise.

[Dr. Frank]

Measurements International has the following brochure...

http://www.mintl.com/media/pdfs/accubridge.pdf

Does this mean all the extra digits (10's of ppb) are meaningless or do they have a useful application?

I have not seen any videos of these in operation so I am guessing they are not as easy to operate as their sales people advertise.

That's a resistance bridge, not a DMM!

Bridge type instruments are much more precise and sensitive.
1e-10 resolution is possible, but 1e-9 is more serious, due to 10nV noise limit vs. 10V max. DUT voltage.
See also IET Labs 242D Bridge specification.

For uncertainty, at room temperature the best known standard is the ESI SR104, and this is limited to about 0.1ppm uncertainty, maybe 0.01ppm by prediction, in a well controlled lab and with very frequent comparison to a Quantum Hall standard.

Therefore, 0.1ppm uncertainty or 7 digits are serious for a non - primary lab.

Frank

[EEVblog]

just curious, how much (ballpark) does it costs?

About US$5500 

[EEVblog]

Therefore, if they write 8 digits on their box, they either must have used something else, an ESI SR104, or maybe measured at PTB (what I doubt w/o a thermometer inside), or they are not very serious.

I can assure you they are very serious.
The unit was calibrated at Germany's national standards lab, and from a brief look at the cal documents, tested for drift at 0.5degC intervals over a large range.
They are working very closely with Vishay to get their very best technology and the resistors are custom designed for them. They are not just buying a stock series resistor sticking it in a box and whacking it on a 3458A.
It took many weeks to characterise and calibrate this resistor for me.

[Dr. Frank]

I can assure you they are very serious.
The unit was calibrated at Germany's national standards lab, and from a brief look at the cal documents, tested for drift at 0.5degC intervals over a large range.
They are working very closely with Vishay to get their very best technology and the resistors are custom designed for them. They are not just buying a stock series resistor sticking it in a box and whacking it on a 3458A.
It took many weeks to characterise and calibrate this resistor for me.

Wow, then congratulations on that fine standard!

All right, as assumed, that's our PTB - Physikalisch Technische Bundesanstalt, maybe they used their Quantum Hall effect facility directly for that. In this case, 5500 bucks would be a real bargain.

And you really paid that price? Are you really goin' volt-nuts?? 

I'd like to see that calibration document, please!!
And a picture of that blue cal sticker on the top, that might be the PTB - blue.

Frank

[TiN]

Whose 10k is more 10kish?
This PDF on VPG say's it's VHA518, very similar to my 1M0000 HZ resistor

[EEVblog]

And you really paid that price? Are you really goin' volt-nuts?? 

I ain't nuts!
They contacted me out of the blue and offered one, it's a new product they are working on.

I'd like to see that calibration document, please!!
And a picture of that blue cal sticker on the top, that might be the PTB - blue.

Yep, I'll scan and post more, plus I plan a video using it to calibrate my Fluke 5450A

[Edwin G. Pettis]

For comparison, gentleman, my ESI SR104 is in excess of 15 years old and exhibits the typical sub-0.1PPM drift per year as is common with these standards.  My SR104's nominal value is at +2PPM (10,000.02 ohms), Alpha is -0.06PPM/°C and Beta is -0.008PPM/°C.  The built in temperature sensor resistor is 10,000.08 ohms with a TCR of +1000PPM/°C and the SR104 also has a thermometer well.

This 'new' resistance standard appears to be starting off well but it is going to take years to find out just how good it is for long term stability, unfortunately for standards grade resistors you can't use the usual tools to predict long term stability except by time alone.  As can be seen by comparison to my SR104, this standard has some more work to be done on it, a very good start though.  The SR104 still holds the top honors in this group and I rather doubt it is going to lose that position any time soon.

The ESI 242D bridge is still exceptional even after all these years, with direct comparison to a SR104, the uncertainty is 0.1PPM or a bit less, the bridge can resolve 0.01PPM or a bit better (I can resolve another digit) by direct comparison.  I can resolve two more digits beyond that by using the standard multiplier but the absolute accuracy degrades a bit because of a slight additional uncertainty added.  Only a DCC bridge can obtain a higher accuracy at 10K or the National Primary Standards Labs.

[ltz2000]

These are not standard Vishay parts, they are:

custom specific made part, together with a special packaging.

http://www.vishaypg.com/foil-resistors/case-studies/study/wekomm_1/

Wekomm engineering paired the VHA518-7 resistor with carefully selected components to form a transfer standard product.

VHA518-7 (= 7 resistors in series)



VHA518 long term drift measurements against the Quantum Hall by the Dutch Metrology Institute:

http://www.vishaypg.com/docs/63620/63620.pdf

VHA518-11 (= 11 resistors in series)

[Edwin G. Pettis]

Hmmm, a case study of essentially one  or two resistors, that is more anecdote than data per se, they do not say just how many of these 'units' were tested, it appears to be just one each and neither one was a 10K unit.  I am also rather curious about Dr.ir. Gert Rietveld's use of the phrase "appeared to be less than 0.5PPM", that makes it sound like there is some question about the measurement.  While I have no qualms about the Dutch VSL, I have always found Vishay's proclamations to leave something to be desired.  The Alpha and Beta quantities are significantly worse than the SR104 and yet they seem to be claiming possibly better linearity of the linearity line, this is conflicting.

The SR104 has a long history behind it and a long track record of proven performance over decades, this supersedes the measurements of a few resistors even over a relatively short period of 5.5 years.  Frankly, I'm not sure the NIST would accept this as a standard in the same performance of the SR104, the SR104 is classed as a primary standard  and therefor must meet very high performance standards.

Just so there isn't any question, I am fully cognizant of the fact that these Vishay (Wekomm) units are made up of quite a few individual resistors, but as a whole, they are still referred to as a single resistor as a unit.

[ltz2000]

they do not say just how many of these 'units' were tested, it appears to be just one each and neither one was a 10K unit.

"Vishay typical" ?

While I have no qualms about the Dutch VSL, I have always found Vishay's proclamations to leave something to be desired.

The document I linked is Vishay marketing material. Most likely VSL will publish / has published scientific article of their experiments.

Bulk metal foil resistors have been used for a long time in primary metrology for AC/DC transfer. But not for anything long term...

[jaxbird]

Look what just turned up:



My 34470A is currently saying it is 10.000200

This is a good read Might not legally apply, but still...

https://www.ftc.gov/tips-advice/business-center/guidance/ftcs-revised-endorsement-guides-what-people-are-asking

[Edwin G. Pettis]

they do not say just how many of these 'units' were tested, it appears to be just one each and neither one was a 10K unit.

"Vishay typical" ? 

  Yes, typically Vishay posts incomplete or 'fuzzy' specifications, 'fuzzy' test results or tests that don't even accomplish what they are supposed to do.  Vishay has done this for decades and the practice still continues.  I know, I've been here for nearly all of it.

While I have no qualms about the Dutch VSL, I have always found Vishay's proclamations to leave something to be desired.

The document I linked is Vishay marketing material. Most likely VSL will publish / has published scientific article of their experiments.

Bulk metal foil resistors have been used for a long time in primary metrology for AC/DC transfer. But not for anything long term...
   

  Precisely, Vishay Marketing BS, it makes the grass greener and much of Vishay's so-called scientific papers have flaws in them and misstatements.  Bulk metal has been around for years but PWW have been around a lot longer and currently surpass many of the claimed Vishay performance data.  Unlike you folks, I've been in the resistor industry for over 4 decades, I have the experience and knowledge which no one else in this forum has an apparent claim to.  Yes, for the record again, Vishay resistors do have some really good attributes but rarely do they perform to the overstated claims of Vishay.  Read back through some of the threads on this forum and some of the professional forums and you will find that this is backed up many times over.

For those of us in the know, some of those purported Vishay scientific papers are just plain laughable and inept.

[EEVblog]

For those of us in the know, some of those purported Vishay scientific papers are just plain laughable and inept.

Have people published detailed research papers in rebuttal?
I have not researched any of this of course, but putting my skeptical hat on, I find it hard to believe that one of the leaders in the field of precision resistors for many decades produces "laughable and inept" scientific papers.
Mistakes? I'm sure that happens, but "laughable and inept"?
Proof please.
And BTW, proof is not "go read the professional forums" and "Unlike you folks, I've been in the resistor industry for over 4 decades, I have the experience and knowledge which no one else in this forum has an apparent claim to."
/skeptical hat off

[Edwin G. Pettis]

Yes, laughable and inept, I can produce some e-mails from Bob Pease, for example who was quite critical of some of Vishay's nonsense.  Alot of the stuff Vishay has put out about PWW resistors has been and still is laughably wrong, they are not experts on PWW resistors, never have been but that has never stopped them from making wrong (possibly intentional) claims about PWWs.

If you really do 'research' it, you'll find that it is inevitably Vishay who has been calling themselves the industry leader for the most part, some of their competitors may not be quite ready to call them that.  I know of many engineers and companies who have tried Vishay resistors in the past (recent as well) and have returned to PWW resistors as the Vishays did not meet specs.  I can give an example of one such case, there are many more.  Vishay is consistent in their fudging specifications over the decades and in some cases have actually ceased production quietly after problems were reported by customers.  As it appears you seem to think I am the only one of this opinion, I am not by far but of course there are people out there who think Vishay is the greatest thing since sliced bread too.

If you have been paying attention to what I write about Vishay, I do not solely bash them on the head, they do make some very good parts of course, but there is also a lot of hoodwinking going on over the years and it is quite surprising how many people are clueless.  It is solely up to you whether or not you want to believe me or not, I have no control over that but there are people who also agree with my position on Vishay and also agree that I classify as an expert in resistors.

The proof, if you want to take the time to find it, is 'out there' and professional forums are generally a qualified source of valid data (not always of course).  If you want skeptical, I had to convince Bob Pease that what I was saying was valid and I did.  Bob was no easy pushover either.

When I get a little time, I'll be happy to post some, and yes, my 40+ years does qualify me as an expert whether you accept it or not, I do accept your opinion, you are welcome to it but on the flip side, what qualifies you to say that I am not what I say I am or my opinions are valid or not?  It does work both ways.

BTW, I made standard resistors for Tegam (before they sold the line off) and my 10K was made from one resistor and it was within 2PPM of nominal.

One more thing, I may sound like I'm swinging a sledge hammer here (I'm told I do that at times) but that is not the intention. 

[EEVblog]

It is solely up to you whether or not you want to believe me or not

No, it's not up to me, it's up to the evidence.