Measurement Uncertainty.....stirring up dust - MU variance for any given calibration

[Hershal]

Here is something for all the 6S folks.....

6S has traditionally dealt with manufacturing processes and the like, and that is good.....but manufacturing and in fact commerce itself.....relies on measurements.....and therefore on measurement uncertainty (MU).

MU is the mathematical description of errors associated with a measurement. Metrology professionals provide MU as a part of accredited calibration. There are many folks who are teaching and developing MU.

Now, there are instances where - in my opinion (a Hershalism only) - the current models - all of which come from the Metrology world - are not valid for some applications.

Now, 6S folks - if you are up to the challenge - try to develop a SIMPLE method to document MU for a given calibration that is compliant to GUM (Guide to the Expression of Uncertainty in Measurement), also available in the U.S. as ANSI/NCSL Z540-2-1997. It must be compliant to GUM or will be instantly rejected by those of us in the Metrology world.

Remember, the influences - and the NUMBER of influences - of MU for any given calibration will vary from one calibration to the next, and vary from type of calibration to another.

Anyone up to the challenge?

Hershal

 

[Marc]

No takers on this one?

 

[Wes Bucey]

Gee. The Cove generally bashes 6S folk. Is it any wonder they take a tip from angels and stay clear of paths they fear to tread?

Most of our 6S visitors (Govind, Bill Pflanz, etc.) are nice, pragmatic people, struggling to keep their own employers afloat. They might not have time to work on such an initiative.

If they did, would it be more to their advantage to publish it in a conventional book or scholarly journal and reap a lot more praise than they might receive here in the Cove?

Like it or not, the reality of WIIFM (What's In It For Me?) prevails in real life as well as corporate life.

 

[Jim Wynne]

Gee. The Cove generally bashes 6S folk. Is it any wonder they take a tip from angels and stay clear of paths they fear to tread?

I'm not sure that's a fair statement from what I've seen; I think there is considerable questioning of SS as a packaged "paradigm" but I don't think that the mortality rate amongst the messengers is particularly high.

Most of our 6S visitors (Govind, Bill Pflanz, etc.) are nice, pragmatic people, struggling to keep their own employers afloat. They might not have time to work on such an initiative.

I think most of the Non-SS visitors are also nice pragmatic people struggling to keep their employers afloat.

If they did, would it be more to their advantage to publish it in a conventional book or scholarly journal and reap a lot more praise than they might receive here in the Cove??

Like it or not, the reality of WIIFM (What's In It For Me?) prevails in real life as well as corporate life.

I agree that it would be unfair to use a lack of response to this particular question, in this particular venue, as evidence against SS in general or any practioners in particular. It is a complex problem to begin with, the sort that doesn't lend itself to internet forum responses, and I don't think SS, for all of its shortcomings, makes any claims to be able to reduce complexity when complexity is an inherent and necessary attribute of a process.

 

[Caster]

Talking to the boss about MSA and GUM

Here is something for all the 6S folks.....

6S has traditionally dealt with manufacturing processes and the like, and that is good.....but manufacturing and in fact commerce itself.....relies on measurements.....and therefore on measurement uncertainty (MU).

Hershal

The SS guy I know starts his projects with MSA studies. So there is an understanding at the system level of measurement variation amongst the SS disciples.

I work in automotive world so my feelings about MU are tempered by Big 3 mandates.

I had a ton of fun on my own personal journey of discovery with MU.

When it was all over, and I could express MU...hey...guess what? No one but me cares.

In auto world what did 17025 do for us? Doubled the price of calibrations. But we do get another page that no one understands.

Just for fun corner an automotive supplier plant manager and tell him all about MU. Wow, I love seeing "the look".

If no one can show the payback of ISO 9000, how would we fare with MU (at least in automotive)? I'm sure it has a place in electronics and optics. Not so sure it matters so much for us who beat on metal.

Yikes, sorry I'm so cranky today.

 

[Jim Wynne]

If no one can show the payback of ISO 9000, how would we fare with MU (at least in automotive)? I'm sure it has a place in electronics and optics. Not so sure it matters so much for us who beat on metal.

I used to have an grizzled old family doctor who took a wonderfully pragmatic view of things. I had a condition that had the potential to require surgery and I asked him if I should see a surgeon about it. He said, "Jimmy my boy, let me tell you something about surgeons. They cut for a living. Never go to a surgeon unless you're sure you need to be cut." The ailment in question was treated with medicine and time, and no surgery was necessary.

I take the same view of statisticians. They do numbers for a living. Sometimes they're allowed to take over, mainly because most of us don't understand the how deep the water is, and because we can't tell the difference between specious answers and reality. MU is a perfect case in point. In all of my 150 years (or so it seems) in manufacturing, I have never seen a problem that could have been helped if I had known more about MU. You are correct in stating that it does have its place down in the bottom of the tool box, but in the words of the immortal Bob Dylan, you don't have to be a weatherman to know which way the wind is blowing.

 

[JerryStem]

We're (hopefully) almost finished with our 17025 re-accreditation by A2LA, it's been going on since October. One of the sticking points has been MU & our auditor, who has been here 3 times, and given us 3 different ways/means to do our MU.

I finally told the A2LA rep last week I will put any number on our scope of accreditation that he wants. I don't care, and neither does any of our customers...

We ended up doubling our old MU values. If this passes, so be it.

Jerry

 

[Hershal]

Time for a well-timed wrench (adjustable cresent from Eskilstuna?) to be thrown into the works.

The VIM (International Vocabulary of General and Specific Terms in Metrology) is the - for lack of a better term - Metrologists' dictionary. It states (and repeated in NIST handbooks) that traceability of measurement relies on two things: an unbroken chain of comparisons to National or international standards, and stated uncertainties at each step. In other words, MU.

Why is MU such a hot topic these days? Part of it is ISO/IEC 17025 requirements, but part of is that one can buy an item that is as accurate as NIST may have in the not-too-distant past, and get it for cheap (comparitively speaking).....meaning for quite a few calibrations, the 4:1 rule is difficult, if not impossible to maintain.

Still, I suspect there is a better way to document MU.....that is faster, easier, cheaper, and still as valid.....

Hence the challenge.

Hershal

 

[Hershal]

Come on all 6S guys.......this should be EASY!!!!!!

 

[JerryStem]

We're (hopefully) almost finished with our 17025 re-accreditation by A2LA, it's been going on since October. One of the sticking points has been MU & our auditor, who has been here 3 times, and given us 3 different ways/means to do our MU.

I finally told the A2LA rep last week I will put any number on our scope of accreditation that he wants. I don't care, and neither does any of our customers...

We ended up doubling our old MU values. If this passes, so be it.

Jerry

Well, got yet another letter from A2LA. Seems someone on the voting council failed it! His response was that it doesn't follow their guide to MU. Nothing about what's wrong, what needs correcting, just "Your wrong, go fix it".

I told my rep. I am done. I have nothing more to offer, nothing more to add. If this is incorrect, after she considered it done, and the assessor considered it done, then I need to know EXACTLY what the voting council member objected to.

If this is not possible, then I get to go thru the appeals process...... Yay.....

Jerry