Electronics > Metrology

Local calibration labs

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Conrad Hoffman:
We have a few local labs and I was looking at their "certificate & scope" documents. They're all about the same, using the same equipment. Unless I'm missing something, they're  not very good in terms of voltnut requirements. Heck, I think I can do better with the antiques in my basement! This is typical- am I missing something here?

try:
Hi Conrad,

First of all, I'd like to thank you for your making your metrology mini lab article series available!

It could be that you are missing something there.

When checking calibration certifications on file the Elmtec company nearby (Germany) states two different figures.
 Their certification distinguishes between dc measurement devices >0,33V <=33V with 22ppm and dc sources between 0,2V and 20V with 6ppm.

Does your lab show similar differences or is there just one entry on file for the range in question?

Elmtec is not an extraordinary lab.

Fluke Germany, p.e. has a certificate entry for voltage references showing 0.2ppm for a 10V reference. This is probably the best you can get here. The only disadvantage with that annoying company is that they even refused to quote me a price for a self-built reference.

I doubt that you can do better just with the 731 models you own...

Regards
try

ManateeMafia:
For 10V DC transfers, there is usually another entry in the Scope of Accreditation. I usually look for a Fluke 732A/B entry as the standard used. If they don't have that entry, chances are they can't support it.

For the resistance, I use a lab in Pittsburg that has good pricing for standard resistors. This was recommended to me by Edwin Pettis.

MisterDiodes:
Correct: A lot of labs aren't setup to calibrate other "high accuracy" equipment.  You really need to talk to the lab manager at your local facility:  Trying to calibrate a 3458a blindly another 3458a + opt 002 is not doing much good especially if that 002 option unit is more than a few years old and not maintained at Loveland, CO.  At that point its golden LTZ Vref has morphed into any other 3458a Vref and the "002 option" is just more expensive voodoo fluff.  If possible, to maintain a 3458a it's just better to buy a 5 yr contract at Loveland, and then they take care of everything when you send in your 3458a for cal (batteries, adj. etc.) And all under warranty.  When you look at final cost, that's really the best value.  Even with shipping (or take a vacation in Colorado if you drive your stuff in yourself).  IF you make a living with your equipment, you don't complain about the maintenance charges.  There is no such thing as "zero drift" in the PPM world.

A real lab will have access to much more than just a 3458a - there will be at least one loaded 734 rack involved with routinely cal'd 732's on board to maintain a good volt.  Or the facility will have a JJA available that's ref'd to NIST, like at Fluke or Boeing in Washington state, two facilities that are local to the Pacific Northwest in USA.

Some well equipped labs are now able to use a "shippable" JJA that goes back and forth to NIST, but you have to check.  That's another option.

If you have your equipment calibrated at one of the cheaper "chain" labs, you're basically just buying paperwork and stickers.  Which is fine for a lot of companies who don't really care about absolute accuracy, they just want that sticker on the front of their equipment to pass an ISO 900x audit (usually).  That's sort of why the cheaper chain labs exist (TransCal, etc.).  A few of those labs are better equipped, but you have to call and talk to them directly.

A lot of times all someone really wants is that magical sticker and cal certificate, and they have no idea to what uncertainty and confidence the equipment was "calibrated" against. 

Do it right and have your equipment cal'd at a real lab. It probably won't be the cheapest, but you get what you pay for.

try:
Hi MisterDiodes,

I had sent you a personal question months ago regarding your LTZ1000 experience.
Would you mind looking at it?

January 16, 2017, 11:26:07 AM    "jumpy" LTZ1000    MisterDiodes

Regards
try

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