Southern California - calibration/metrology facility?

[Rax]

Hi all,
I'm a bit at the end of the rope here, trying to find a suitable local facility (or semi-pro on steroids?...) that's able and willing to "calibration-verify" a few instruments and standards I have here (which I'm pretty sure to be able to pass verification):

• Fluke 8502A
• Data Precision 8200
• ESI SR1 set of resistors

Is anyone in this community aware of such? I'm South of LA, one third towards San Diego, but can drive all around LA metro for the right place.

There's probably no place on earth so laden with such joints (due to all the aerospace, military, physics, etc. activity around here), and yet, I can't seem to find one that's committed, serious, and performs all services. For instance, having the resistors measured seems like a no go for the place that seems the most willing currently.

Thank you all for your input.

[Conrad Hoffman]

No idea what's out there but my experience is almost all cal labs are paper-centric, as are their customers. Finding ones that are actually interested in accuracy and correct methods is harder than you might think.

[CatalinaWOW]

It has been decades since I resided in that area, but at that time the big aerospace companies had captive calibration facilities with no interest in outside work.  I don't know how the universities work, if they even care about calibration.  But overall it isn't too surprising to me that there is not a huge calibration industry in the area.

[mendip_discovery]

Search for 17025 accredited labs in your area. Look at the schedule and see what they have to offer.

I have to agree with Conrad. I fear the lab I work at has mostly customer who care about a bit of paper. I try my best but I am limited on the budget I can spend. Sadly the industry is good at making money even without the most expensive kit.

[Rax]

It has been decades since I resided in that area, but at that time the big aerospace companies had captive calibration facilities with no interest in outside work.  I don't know how the universities work, if they even care about calibration.  But overall it isn't too surprising to me that there is not a huge calibration industry in the area.

I both agree and disagree with you. It's likely true the calibration industry in the area is largely captive to the aerospace programs (and a lot of other similar top shelf science governmental and private pursuits), from the military to the space program. But I'd definitely not agree the footprint of the calibration industry is small - it may in fact be just about the most generously endowed area in the world in this aspect. My short list is currently about 15 labs (within a relatively short drive by Los Angeles metro standards), and this list has both been shrinking (due to unfit places) and growing (from better offerings, mostly by referrals from places I've wrote off).

I'm still looking (and welcome recommendations), but I seem to narrow down to a few places that may be up to the task. Very encouraging.

[Rax]

No idea what's out there but my experience is almost all cal labs are paper-centric, as are their customers. Finding ones that are actually interested in accuracy and correct methods is harder than you might think.

Conrad - interesting you should  put it this way. Some of the recommendations I got (I called maybe 20-25 places yesterday and today, from high end cert labs to instrumentation repair places) were exactly in these terms - which lab would give me a real service (to be chosen if I truly am interested in accurate instrumentation) and which would just glaze over the tests and print out a piece of paper cause I'm paying for it.

[J-R]

After all that research, any recommendations for a place that is somewhat budget-friendly?

[Rax]

After all that research, any recommendations for a place that is somewhat budget-friendly?

Absolutely, and I'm very happy with it. I will let you know by PM. I'd want to check with them, at a minimum, if they'd appreciate the advertising, as they're very busy.

[J-R]

Well, a top three list would be OK as well.  Based on your conversations...

[timeandfrequency]

As far as I know, there are different services you can purchase and I would say it is wise to speak with the calibration lab you have selected to be aware of the type of services they provide and how they perform TE verification, calibration and repair.
Try to contact one of their repair technicians. These guys are more likely to discuss how the process is performed and will provide detailed information.


Different levels of service
a) The vanilla service level is only the 'verification' that checks whether your TE meets its specifications. If so, you get a one-page report with a (nice) stamp, brand, model and serial number of your TE.

b) For an additional charge, you can get a detailed verification report which lists all the tests/ranges that have been verified, their actual deviation and the measurement uncertainty.
The detailed verification report should normally include a list of all equipment used by the calibration laboratory to perform this verification. For each device, you must have its brand, model number, serial number, last calibration date, next calibration due date.

c) In case the result of at least one test is FAIL, the TE enters a 'calibration' process, where new cal parameters are calculated and stored, or for vintage stuff, the required trimmers are adjusted manually. Once the calibration OP estimates its work done, the TE is handed back to the 'verification' department. In that case, if you ask for b), the report usually includes the first verification results (having at least one failed test) and the verification results after calibration. The latter will have to show that all of the verification tests are PASS.
e.g. : I recently had to sent my MW powermeter back to the manufacturer for cal service : the detailed report they sent me contains 22 pages.

d) In the event that the 'calibration' cannot be carried out successfully, the owner is informed of this situation and can request a 'repair'. The owner can also refuse the repair and the TE is returned to him as is, for a nominal fee.
A 'repair' is necessary if a part has drifted so far that the span of the calibration parameters cannot bring the TE back to specification.
Calibration will also be impossible if a part/assembly is defective, if connectors or solder joints have shaky contacts, if essential accessories are missing, if traces have disappeared due to electrolyte spillage, if mains overvoltage or a shorted Tantalum capacitor killed the PS, lightning damage, improper use of the TE which fried the whole input board, equipement was drowned, stored/used in a hazardous/corrosive environement, internal hard disk failure, backup battery empty leads to the loss of all cal coeficients, if there is mechanical damage (connectors, screen, front plate, case, cables,...), in case of multiple damage because the device fell from the moving truck or even if the owner tried an in-house repair and opened the TE with a crowbar without removing the screws. These kinds of things happen.
If the owner wants the TE repaired, the repair technician will estimate the cost of the 'repair' and send a pro-forma invoice for it.
Once this pro-forma invoice has been accepted by the owner, the TE is repaired and then handed over to the 'calibration' department c). Once the latter has been carried out, the TE goes back to the 'verification' departement for a) or b).
The owner can request detailed information on what was actually repaired and what parts/assemblies were replaced. This type of information can be printed in the detailed report, if provided, or in the final invoice, which includes all repair, calibration and verification costs.

[Rax]

timeandfrequency - that's an OK, if wordy summary of what can be expected.

My examination of the facilities I talked to (maybe a bit over a dozen, all within driving distance, though, depending on what I was looking for, many would extend a capability to other facilities from their network across the US) was always in terms of:

• basic calibration (cheapest) which is essentially a pass/fail, as I understand it. I can't imagine anyone wanting this other than state or county labs just wanting their equipment checked and stamped, or they trash it. "Good enough for government work" kind of thing.
• Z540-1 usually includes before/after results. This to me is critical, as it provides me with actual, accurate values for different points that are checked by the procedure. This I can then use in my own environment as "objective" datapoints, and is my default choice.
• ISO 17025 - most expensive; includes uncertainties. As much as I entertain the concept, in my book, it doesn't really justify the additional expense for me

Most labs would declare their used equipment (for the services one requests), including their state of calibration (when due). One even shared their "scope of accreditation," which essentially includes all their equipment with associated data for all covered standard measurements.

One lab even declared (unprovoked) some reserve with their provided TAR with one of my instruments in a certain range. Homework done! No wonder this became my favorite, aside from also being the most affordable one. Double whammy.

The other big factor for me was their willingness to "adjust." Most places would not, actually. Which I get, not getting into the messy business of adjusting units - and the likely slippery slope of ending up repairing - makes a lot of business sense. Only checking is predictable, easy to make lucrative, and so on. The place I like does adjustments, so that's a big plus. That said, I (and power friends - you know who you are) haven been able to adjust units for passing cal, so maybe this element is not quite so essential, but it's nice to know it's a possibility. Again, most places would not touch adjustments in older equipment.

Getting through the "sales storefront" wall of reps is huge. If you can get to the back of the shop to the actual tecs, that's pretty nice, and you shouldn't necessarily expect it. 

FYI - some places charge half the cost for an unsuccessful calibration. So, if it passes, it's full cost, if it doesn't they return the equipment for half the cost. I don't know if this means they declare the exact point of failure and data on it, but it didn't remain a big factor for me as other aspects disqualified that option.

Hope this helps orient someone else in the same conundrum. I spent several weeks talking to a bunch of places, both over many phone calls, and exchanging dozens of emails, so I'm hopeful I can save some time for others in this community.

[timeandfrequency]

I confirm : the cal report I received for my MW powermeter indicates that the procedures used were in line with ISO 17025.

[mendip_discovery]

I confirm : the cal report I received for my MW powermeter indicates that the procedures used were in line with ISO 17025.

Often labs use the same kit as they do for 17025. It's just they don't want to have the hassle of the faff to do the certificate they way that expected. But also used by some labs that aren't 17025 accredited to hide that they are not.

[alm]

c) In case the result of at least one test is FAIL, the TE enters a 'calibration' process, where new cal parameters are calculated and stored, or for vintage stuff, the required trimmers are adjusted manually. Once the calibration OP estimates its work done, the TE is handed back to the 'verification' department.

Be very careful with using the word calibration to refer to adjustment when talking to calibration labs. The International Vocabulary of Metrology makes clear that the word calibration does not cover adjustment. Even though some old manuals might use the word differently, I would avoid any confusion.

If you want adjustment, ask for calibration with adjustment, and be clear on when this adjustment happens. Generally this is if parameters where close or outside some limits, but what those limits are, and what close means, might vary. For example do they use guard banding? 1 year manufacturer limits, 90 day or 24h limits? Or even arbitrary limits based on the cal labs abilities.

[Rax]

c) In case the result of at least one test is FAIL, the TE enters a 'calibration' process, where new cal parameters are calculated and stored, or for vintage stuff, the required trimmers are adjusted manually. Once the calibration OP estimates its work done, the TE is handed back to the 'verification' department.

Be very careful with using the word calibration to refer to adjustment when talking to calibration labs. The International Vocabulary of Metrology makes clear that the word calibration does not cover adjustment. Even though some old manuals might use the word differently, I would avoid any confusion.

Very true, in terms of language.

• "Calibration" is essentially always understood as a mere verification procedure (against some criteria, depending on the details). I don't think this ever implies opening the hood.
• "Adjustment" I found to be the magic word. It not necessarily implies popping the hood (so it could just be closed case "software calibration") and it usually involves performing one of the adjustment procedures in the SM or otherwise. This is an exceedingly rare service, so if you find a place that commits to this, make sure you triple check both their reputation and capabilities, and start building a relationship.

[timeandfrequency]

Your are right : with recent TE, only a repair action requires to open the hood. Calibation and adjustment is software driven.
Even moving a jumper to allow cal parameters update is vintage.
But, changing the backup battery still requires to open the case...
Don't really know why the manufacturers are still a bit reluctant in using flash memory devices.

Wording : 'Guardbanding' and 'Adjustement' (and ISO 17025) are clearly mentioned in the report I received (see snapshot) and, as you underscored, the differences in meaning must be taken into account.

Often labs use the same kit as they do for 17025. It's just they don't want to have the hassle of the faff to do the certificate they way that expected. But also used by some labs that aren't 17025 accredited to hide that they are not.

As indicated in a previous post, my R&S MW powermeter was sent to the Rohde & Schwartz headquaters in Munich, Germany, where the manufacturer's cal/metrology lab took care of it.
I can barely imagine that the european foremost TE manufacturer falsifies a cal report and botches the calibration and adjustement procedure about a TE of its own brand.
But, if you have serious proof to provide, I'm interested.

[Rax]

Your are right : with recent TE, only a repair action requires to open the hood. Calibation and adjustment is software driven.

Not sure who you were addressing above, and you have a qualifier ("recent TE"), but I don't think I really agree with that statement. The vintage of equipment I tend to look at (so I can speak about) carries both software and hardware calibration, and they do completely different things (although they are typically seen as incremental in relative terms - so one could do a software cal fairly often, but a hardware cal is involved and should stick for quite a while). A full "performance verification followed by adjustment calibration" typically involves both (at least by SMs).

[alm]

• Z540-1 usually includes before/after results. This to me is critical, as it provides me with actual, accurate values for different points that are checked by the procedure. This I can then use in my own environment as "objective" datapoints, and is my default choice.
• ISO 17025 - most expensive; includes uncertainties. As much as I entertain the concept, in my book, it doesn't really justify the additional expense for me

It depends on how close the instrument your are having calibrated is to the uncertainties of their process. The process might have low enough uncertainties to say if a measurement is over or under the limit with 95% (or 99%) confidence. But that doesn't necessarily mean that it will give you an accurate representation of how much it is over or under. For that I would want to see the uncertainties of the calibration points. Again, this depends on the meter and what they are set up with. For a 3.5 DMM I would take the value from any multi-function calibrator as gospel relative to the meter, but if you have a Fluke 5520A multi-function calibrator calibrating a HP 34401A DMM, then the calibrator has a 9 ppm/90 day basic uncertainty (plus whatever other uncertainty there is in the traceability chain), while the meter has a 20 ppm/90 day uncertainty. That is barely good enough to judge if the meter is within that 20 ppm with heavy guard banding, but I certainly wouldn't put much faith in those values to make the meter much more accurate.

I recommend to read the Fluke app note Calibrating the Hewlett-Packard 3458A DMM with the Fluke 5720A Multifunction Calibrator. It obviously talks about a different class of calibrators and meters, but it explains how to use guard banding to compensate for a low test uncertainty ratio and shows the math. Based on that, you might also deduce that not all values on that report would be as useful for making your readings more accurate.

I would say uncertainties are especially important if you use different cal labs, or the cal labs use different procedures (like buy a new calibrator), over time. Since it allows you to determine if a change over time is actual drift or might just be noise due to the uncertainty of the calibration.

[Rax]

For a 3.5 DMM I would take the value from any multi-function calibrator as gospel relative to the meter, but if you have a Fluke 5520A multi-function calibrator calibrating a HP 34401A DMM, then the calibrator has a 9 ppm/90 day basic uncertainty (plus whatever other uncertainty there is in the traceability chain), while the meter has a 20 ppm/90 day uncertainty. That is barely good enough to judge if the meter is within that 20 ppm with heavy guard banding, but I certainly wouldn't put much faith in those values to make the meter much more accurate.

Not sure if this is entirely apples to apples, but that's why I found further reason to choose the lab that transparently declared their marginal TAR measurements vs. my units where they were less than 4:1 (even if not bound by the confines of a 17025 spec by work order).