Whatever happened to Wekomm?

[splin]

Their website is still up but it looks like a zombie site. Their standard resistor product got a bit of a rough ride here a few years ago - I hope we didn't (help) drive them out of business?

Did anyone here buy one or know someone who did? If so, how did it perform?

[Andreas]

Hello,

perhaps one reason (for the website) is that the distribution of their resistors is exclusively by datatec:

https://www.datatec.de/search?sSearch=wekomm

with best regards

Andreas

[branadic]

@ splin

as you might have noticed, Wekomm was very busy working on A1 and A3 board of 3458A. Furthermore, they are in production of precision resistor standards, that are distributed by Datatec, as Andreas already linked to.
Beyond that, they are in coorporation with the german national standard lab PTB. Their contract was extended by another 2 years, as announced on 27.01.2020 here (third entry from the top):

https://www.ptb.de/cms/nc/meta/suche.html?tx_kesearch_pi1%5Bsword%5D=wekomm&x=0&y=0

Being a SME with a handful of employees only, I'm sure they are still busy with their daily work, saving their income. They will also join us on MM2020.

So Wekomm is far away from being driven out of business.

-branadic-

[splin]

as you might have noticed, Wekomm was very busy working on A1 and A3 board of 3458A.

No I must have missed that - I only saw references to a German company but no name. It's interesting that Keysight chose a small company for this work, but I guess it's more about finding the right expertise.

I'd also guess that this doesn't necessarily mean that Keysight don't have the relevant expertise in-house but the chances are they weren't available given they would likely be in demand to work on their large range of other test equipment.

Furthermore, they are in production of precision resistor standards, that are distributed by Datatec, as Andreas already linked to.
Beyond that, they are in coorporation with the german national standard lab PTB. Their contract was extended by another 2 years, as announced on 27.01.2020 here (third entry from the top):

https://www.ptb.de/cms/nc/meta/suche.html?tx_kesearch_pi1%5Bsword%5D=wekomm&x=0&y=0

Do you know if the PTB are using the Wekomm resistance standards? If so are they likely to publish their experience with them?

So Wekomm is far away from being driven out of business.
-branadic-

That's good to know though my comment was very much tongue-in-cheek. 

[branadic]

Do you know if the PTB are using the Wekomm resistance standards? If so are they likely to publish their experience with them?

Yes they do. By the way, there is also a paper about the resistors development available:

https://ieeexplore.ieee.org/document/8501086
DOI: 10.1109/CPEM.2018.8501086

-branadic-

[Vgkid]

Anyone have a non ieee link?

[doktor pyta]

Just paste DOI number here:
https://sci-hub.tw/

[splin]

Do you know if the PTB are using the Wekomm resistance standards? If so are they likely to publish their experience with them?

Yes they do. By the way, there is also a paper about the resistors development available:

https://ieeexplore.ieee.org/document/8501086
DOI: 10.1109/CPEM.2018.8501086

-branadic-

Many thanks for the link.

Interesting paper, but not for any new metrological insights. The paper is about developing new standard resistors for the PTB; this paper describes measurements taken in 2017 on a Vishay VHP101 based standard resistor. Wekomm's existing standard resistors date back to 2015 or so, so presumably this means they are looking to develop a less costly version.

The paper doesn't give much away, showing the results for a single VHP101. It's not credible that they would go to the presumably great expense of testing against a quantum Hall resistance standard, and then only testing a single example - I assume thy would have tested a least 10 or 20 samples to get useful statistical information.

I say "presumably great expense" but maybe the PTB are offering free or low cost access to their quantum Hall standard as quid pro quo for eventual access to 'low cost' secondary resistance standards?

I guess it doesn't make commercial sense for Wekomm to reveal any more information (to competitors) than the minimum required to serve the purpose of this paper. Which is what exactly? Marketing to show your metrology credentials working with the PTB? A requirment imposed on them by the PTB to publish 'results' as part of their working agreement?

In any event, the paper is not very enlightening other than it shows a single example of a VHP101 which drifts downwards, over a period of 9 months, almost linearly, at a rate of approximately 0.4 x 10-6/year. Let's ignore the approx 1.2ppm drop over the first 6 months or so which could be attributed to recovery from thermal or physical shock or the like, and especially ignore the sudden 0.4/0.5ppm drop in Jan 2017 (somebody dropped it?)

That is a bit greater at, 2.4ppm/6 years, than Vishay's datasheet "Shelf life stability: ± 2 ppm typical after at least 6 years". Of course the drift will may well settle down between 9 months and 6 years so Vishay's typical could be achieved.

I consider most of the points under 'DESIGN CONSIDERATIONS' to be fluff, albeit sensible considerations. I expect an unhoused VHP101 would perform just as well.

Zlymex describes how he made a VHP101 based standard in 2008 by selecting 4 from a batch of 50 (selected for TC only) with:

https://www.eevblog.com/forum/metrology/teardown-standard-resistors/msg892700/#msg892700

The result was outstanding -  stability showed almost no drift (< .1ppm?) over 5.5 years,

TC: α = -0.027ppm/K, β = -0.0007ppm/K^2

Compare that to his two SR104s (which typically drift < .1ppm/year), from:

http://bbs.38hot.net/thread-1352-1-1.html

SR104 #1 α = -0.092ppm/K, β = -0.033ppm/K^2

SR104#2  α = -0.135ppm/K, β = -0.060ppm/K^2

We don't know how what happened to those VHP101s between 2008 and 30th Oct 2010.

His results seem to have been much better than his SR104s for a fraction of the cost. The big question is whether he just got extraordinarily lucky wrt the stability of his resistor(s). I certainly would not question his metrology abilities given the high quality information he posted on these forums and his access to top of the line standards and test equipment.

0.1% VHP101s cost around $22 if you buy 500 at a time, probably quite a bit more at qty 50 or less (anyone know). You could probably buy 50 for somewhat less than the cost of a Wekomm and probably less than a used SR104. Then you'd have to get them calibrated but you could likely more than cover the cost of several high quality calibrations with the proceeds from selling the 46 remaining VHP101s!

[branadic]

Wow, so if I get your statement right, Zlymex is more to trust than a company that sells precision resistance standards. That is tough.
And now that you showed us how easy it is to build a resistance standard, would you mind to build them for us and sell us calibrated and predictable resistance standard for a fraction of the price Wekomm is asking for? Let's say 500€? That would be great. Is one year from now on okay for you to do it? Can you might send first samples by the middle of this year? Perfect. 

Okay, no more joking. What I saw and what I was told, the first resistance standards used Vishay VHA518 tube resistors. This times are gone and they now use resistor elements that are fabricated by Vishay, but are based on a design by Wekomm, using their own metal foil and are no longer packaged by Vishay, but a bare resistor element that Wekomm assembles on their own.
I think you'd agree, that if if you have a company with employees to pay and if that improvement you made helped you to make a more longterm stable but also predictable resistor, you would not make all this information public to help your competitors to copy you, right?

But if you still believe you can do it any better for the fraction of the costs, I'm the last one stopping you from doing so and presenting your results and insides right here for free. 

-branadic-

[dietert1]

In my opinion this thread isn't about who can do better or cheaper but about the question whether sup-ppm resistor metrology is a business model or not. If you consider the prices Wekomm asks and you assume they are one or two engineers there everybody can estimate how many they sell per month. My estimate would be less than ten. I'd consider that business as fragile and the original question as justified.

@branadic: Can we expect some insight from the talks in this years meeting?

Regards, Dieter

[branadic]

@ Dieter

Wekomm is an electronics engineering company, their work on 3458A and the precision resistor standards are just examples of activities in the metrology field. They are involved into other developments, all related to electronics engineering.

Considering the price of their resistance standards I'm sure you can't beat them. It's not only to build a resistor, but it takes a lot of time and calibrated gear to characterize them. Though I can't afford them myself for hobby use.

You can ask Guido Weckwerth any question you want, but I can't tell you which questions will be answered. That is only up to him.

-branadic-

[splin]

Wow, so if I get your statement right, Zlymex is more to trust than a company that sells precision resistance standards. That is tough.

Of course I would - by far! I'm sorry I probably didn't make that clear so I'll repeat it: "of course I would - BY FAR!!!!!!!" Especially over "a company that sells...".

Hmm, perhaps I should set up a company and start selling precision resistance standards in the near future - so you should start trusting me my company rather than established experts in the field who aren't companies?

Trust has to be earned and Lymex has done that in spades posting a great deal of high quality information, test results, teardowns of metrology gear (including Wekomm's standard resistor!) etc. both here and on bbs.38hot.net.

Wekomm on the other hand haven't - at least with respect to standard resistors. They have been selling their resistance standard for five years now and yet the only information I can find as to the stability performance was a paper published in 2015, pushing the virtues of using Vishay's VHA518-7 and used in Vishay's marketing and the paper you linked which documents tests on a Vishay VHP101. Both of which are now completely irrelevant as, according to your new information, Wekomm are now using a different resistive element - a Vishay BMF element mounted by Wekomm.

Just to be absolutely clear, I've no doubt that Wekomm are a high quality engineering company and, better still, likely an engineering led company unlike the finance driven companies such as Fluke (Danaher Corporation) and Vishay. I'm quite sure that Keysight would not have employed them to work on the 3458A update if they weren't excellent engineers. I wish them all the best.

But their marketing sucks *big time*. Assuming anyone knows they make a resistance standard and visits their website, would be seriously dissapointed. The website is barely functional and pretty much says "we don't have the time or resources to provide you with any information about our 'high quality and very expensive product' so go and visit our German only (as far as I can tell) distributor's website where you can download a German only version of the datasheet".      (It would be rude to include as many facepalms I believe this really deserves!).

And then the datasheet content.   

It has changed from the 2015 version. I've no doubt there is a proper English version of the datasheet but I can't find it so here is part of the Google translated version from the www.datatec.de website:



Where to start?

1) No tolerance specified. It may be calibrated to .1ppm but I wouldn't be very happy to buy a 10K standard resistor that is 1% off nominal. I'm sure they are at least .01% or better so why not

2) WTF is going off with those maximium voltages and currents? 1mA through a 100Mohm resistor is going to be a just a little bit more than the 500V maximum specified. Same for many others. I'm quite certain that Wekomm understand ohm's law so why, oh why couldn't they bother to get someone to proof read the datasheet? Is the 100ohm resistor really good for 250mW operation unlike all the other values?

3) "Repetition error (hysteresis)

"Repetition error (hysteresis): 30 ° C to 20 ° C to 30 ° C: negligible error." 

That's good but the storage temperature spec is 0 to 40C. So what is the hysteresis error after I've stored my 'standard' at 0C and/or 40C?

And now that you showed us how easy it is to build a resistance standard,

I didn't show any such thing as you know perfectly well. I'm not here to attack Wekomm - this thread was genuinely a request to find out if there was any more long term stability information available wrt. the RS9010. It turns out there isn't, especially because they have substantially changed the construction of the resistance standard over time.

would you mind to build them for us and sell us calibrated and predictable resistance standard for a fraction of the price Wekomm is asking for?

Predicatable? Wekomm haven't, as far as I can find, published anything about the drift characteristics of their (current) RS9010A standard. As their spokesperson perhaps you can elucidate?

I'm sure they are a great company, but since you chose to have a go at me rather than address any of the points I raised I have to assume you have decided to place more importance to defending your colleagues/contacts at Wekomm than taking an objective viewpoint.

Let's say 500€? That would be great. Is one year from now on okay for you to do it? Can you might send first samples by the middle of this year? Perfect. 

500€?  Why not just buy a VHP101 for considerably less? Vishay's datasheet specs are 2ppm/6 years typical drift compared to the Wekomm's .5ppm/year. Who are you going to believe?

Vishay's temperature coefficient specs attract a lot of derision suspicion but some posters here, including Lymex, have confirmed the drift claims. As far as I can see Wekomm haven't demonstrated that their product is any better than a VHP101.

Okay, no more joking. What I saw and what I was told, the first resistance standards used Vishay VHA518 tube resistors. This times are gone and they now use resistor elements that are fabricated by Vishay, but are based on a design by Wekomm, using their own metal foil and are no longer packaged by Vishay, but a bare resistor element that Wekomm assembles on their own.

OK, so they have cost reduced their first effort?

I think you'd agree, that if if you have a company with employees to pay and if that improvement you made helped you to make a more longterm stable but also predictable resistor, you would not make all this information public to help your competitors to copy you, right?

As far as I am concerned they haven't demonstrated anything. Improvements or otherwise. Could you link to *anything* relating to their current product? As to making the information public, it's called marketing; don't you think potential customers might want to know how the product performs?

But if you still believe you can do it any better for the fraction of the costs, I'm the last one stopping you from doing so and presenting your results and insides right here for free. 

-branadic-

I'm not the one trying to sell some ridiculously overpriced resistor. The onus is on Wekomm to explain why their resistor justifies the price. Unfortunately, because (according to you) they have changed the design they presumably can't show any long term drift data.

And why are't they explaining the change in design themselves rather than using you as their mouthpiece?

[EDIT] Added missing datasheet

[branadic]

First of all, I'm not the voice of Wekomm. You asked the forum and now you don't like the answer, that is against your opinion.

If you need any information that is not given on their website or the datasheet, what stops you from contacting Wekomm yourself if you're really interested in the resistors, instead of attacking them here, because they don't present you everything you want to know bite-sized? And by the way, what is different to almost any other measurement product you can buy today, with almost no information about it in the manual?

You went all the effort and energy to post your opinion here instead of contacting Guido Weckwerth to get the answers you want.

I was interested in Wekomm myself after MM2019 last year, so I called them and visited their company a few weeks later. Mr. Weckwerth spent many hours to show me his company and I had a great discussion with him.

But at the and I don't mind whom you trust, even if it is Santa Claus. And I don't give anything on marketing, unless the product can convince.

-branadic-

Edit: You are welcome to join the Metrology Meeting 2020 and ask Wekomm any question you like, as long as the questions are objective.