EEVBlog "Calibration Party"? - Page 1
Forum section: electronics / general

author: Smokey
author_rank: Super Contributor
timestamp: October 09, 2012, 09:39:24 pm
content: Hey guys,I just had an interesting thought. (Bear with me here, I swear I'll bring it back to electronics in a bit.)I was reading a story about guys that make their own rifles in the USA. What they do is they buy aluminum castings that have been 80% machined already because that is the limit they can be legally sold without a firearms dealer license. That last 20% you have to do yourself to make it legal and it is most easily machined on a real milling machine, preferably CNC, which most people don't have. So what they do is get a group of people together and have a "machining party" at someone's house or shop that has a milling machine and everyone takes turns finishing machining their casting and hanging out. Whoever owns the machine has the people pitch in some money to cover costs and whatnot, but it sounds like it's more about hanging out.Ok. Back to electronics....Now it sounds like some of you own or have open access to some really high end gear like bench meters with huge accuracy/resolutions and official up to date calibration certificates and such. Wouldn't it be cool if we could get a group of people together and have an eevblog "calibration party" where we could bring our old out of cal gear and sync it up a known reference? It wouldn't make the gear official or anything, but with all the ebay specials it would be way better than nothing. You could even make a couple bucks and get to hang out with some like minded nerds.I'm not sure if there is a high enough concentration of us in one particular area outside of Australia maybe, but it sounded like a good idea in my head at least.

author: Psi
author_rank: Super Contributor
timestamp: October 09, 2012, 10:23:41 pm
content: One word. Hackerspace

author: Smokey
author_rank: Super Contributor
timestamp: October 09, 2012, 10:26:29 pm
content: I've never been to one, but I get the impression they get their stuff off ebay like the rest of us.

author: tom66
author_rank: Super Contributor
timestamp: October 09, 2012, 10:33:33 pm
content: My workplace pays only £25 to calibrate a scope as they do all of them every year along with the meters and other equipment so they get a discounted price.I considered getting my old HP scope cal'd but I'd sold it before then and got the Rigol.But I will have to ask about my meters - if they can be calibrated. One of them is ideally 0.009% or something when cal'd.

author: TorqueRanger
author_rank: Frequent Contributor
timestamp: October 10, 2012, 12:59:00 am
content: I would come but I live in the U.S.A and you guys talking about Electronics is like Chinese to me lol...

author: Jimmy
author_rank: Regular Contributor
timestamp: October 10, 2012, 02:09:35 am
content: +1 for goto hackerspace

author: Psi
author_rank: Super Contributor
timestamp: October 10, 2012, 02:38:55 am
content: Chances are pretty good at least one member of a hackerspace will have a calibrated unit others can calibrate off.

author: bullet308
author_rank: Frequent Contributor
timestamp: October 10, 2012, 04:16:40 am
content: Perhaps we could develop and pass around some cal standards of our own...

author: Simon
author_rank: Unknown
timestamp: October 10, 2012, 06:03:48 am
content: Quote from: Psi on October 10, 2012, 02:38:55 amThat is not necessarily how calibration works.

author: T4P
author_rank: Super Contributor
timestamp: October 10, 2012, 09:07:44 am
content: Not the case for global hackerspaces ... Not mine for sure. It just sucks bawss.I would certainly love a calibration party though

author: EEVblog
author_rank: Unknown
timestamp: October 10, 2012, 09:31:02 am
content: Quote from: Simon on October 10, 2012, 06:03:48 amNo, not in a formal sense. But for us punters it's plenty good enough for everyone to bring their meters along and spot check them against a formally calibrated unit and order of magnitude or two better. So it's not a bad idea in theory.I've got that MV-106 DC voltage standard for example, whilst not formally "calibrated", confidence is high that it would be good enough to cal check almost any meter.Checking your meter is one thing, but actually performing calibration adjustments is another thing entirely of course.A Fluke 87 for example must (IIRC) run through it's entire cal process on every range with exact values you can only get a from a high end calibrator. You can't just spot adjust DC volts or something.And my Gossen for example requires PC connection and special serial commands in order to tweak the EEPROM values for cal.Dave.

author: Simon
author_rank: Unknown
timestamp: October 10, 2012, 12:00:36 pm
content: Quote from: EEVblog on October 10, 2012, 09:31:02 amAnd that is what a proper calibration is, achievable on low end stuff if you have mid to high end stuff around that is proffesionally calibrated. checking a fluk 87 against another fluke 87 wouldn't quite cut it, just give a rough idea. Yes calibration is actually a misused term.

author: AndyC_772
author_rank: Super Contributor
timestamp: October 10, 2012, 01:08:21 pm
content: I have a properly calibrated Keithley model 2000 (6.5 digits), and I can't believe I'm the only one. It's not a super accurate metrology grade instrument by any means, but it's much more accurate than most handheld meters, and would certainly do as a comparison to be able to say "my meter reads 0.2% low" or whatever.The issue with actually recalibrating meters is completing the cal sequence can require the ability to generate some signals which can't be synthesized easily - for example, accurate high voltage sine waves. Without being able to generate every necessary signal, the cal sequence won't complete.

author: SeanB
author_rank: Super Contributor
timestamp: October 10, 2012, 03:17:15 pm
content: I can do mass from 5milligrams to 35kilograms........... Accuracy to 3 decimal points as well, just had them done, an they have not changed from last time, I take care of them. On the 20kg piece you are allowed an uncertainty of 1.2 g in mass.

author: Unknown
author_rank: Unknown
timestamp: October 10, 2012, 04:16:47 pm
content: I'm lucky, I haven't built anything that has required a small "window" of accuracy more than my old ebay gear can give. I'm still pretty much learning but as I progress, that "window" is starting to get smaller; I'm considering getting 1 piece of test gear calibrated to use as a reference for my others. So the Cal party idea is a good one, if only to at least to know how far off my gear is; so I know it's limitations for any future projects.

author: saturation
author_rank: Super Contributor
timestamp: October 10, 2012, 05:31:31 pm
content: So long as you don't get your hopes too high, a party can work, but mostly as a socializing tool to get people together. In an uncontrolled setting by untrained users, you can probably get away with .01% accuracy for DMM type devices in 10V and 1A modes, but at the next order of magnitude and beyond, technique, better cables, and a controlled setting [ at least temperature and humidity] increasing matter. For a 6.5 digit meter and up, it will be mandatory. You won't be able to test higher voltage ratings or amp ratings without safety concerns, and the lower range mA or uA settings without electrical noise and environmental variation concerns.

author: Bored@Work
author_rank: Super Contributor
timestamp: October 10, 2012, 06:05:19 pm
content: Doesn't Dave know someone at a calibration lab?Maybe he could arrange for a special calibration event there? Special prices, during a limited timeframe, for a limited set of devices (e.g. only one or two brands/types of popular hobbyist multimeter), for only a certain number users, no other service than adjustment, devices need to be send in, all costs to be paid in advance by the device owners. Users nearby could then meet for a drink at a certain date and pick up their meters in person (not necessarily in that order).Or after the µSupply a µReference? A good COTS voltage reference with buffer on a PCB, and the calibration lab measures them (no adjustment) in a controlled environment and provides them with a calibration "certificate" for an extra fee which Dave adds to the selling price.

author: saturation
author_rank: Super Contributor
timestamp: October 10, 2012, 07:22:22 pm
content: That's a great idea, maybe more like a group rate or a guided tour of the cal lab? Its often difficult to get a mass of people into a cal lab because their body heat could raise the internal temps of the lab enough that it won't be at the 25C they need.

author: ColinB
author_rank: Contributor
timestamp: October 10, 2012, 07:36:41 pm
content: Quote from: saturation on October 10, 2012, 07:22:22 pmLOL?! I'm not sure if you're serious... but it's interesting and funny either way.Is the cal lab itself strictly controlled to 25C or do they use environmental chambers to keep equipment at a fixed temperature and humidity?

author: robrenz
author_rank: Super Contributor
timestamp: October 10, 2012, 08:00:11 pm
content: In a serious mechanical metrology lab the temperature control system maintains 0.1deg C and has provisions to minimize the vertical thermal gradient in the room. Too much thermal input (too many bodies) can exceed the capacity of the system).I dont think Electrical labs are quite as demanding and just like mechanical if better temp control is needed it is usualy done in a smaller confined area often with liquid bath or shower systems. (like precision resistors in oil baths)

author: Alana
author_rank: Frequent Contributor
timestamp: October 10, 2012, 08:55:12 pm
content: Great idea!And i would also include electronics labs in highschool or technical univ as means of getting your DMM checked. At lest i should be able to check mine this way.

author: EEVblog
author_rank: Unknown
timestamp: October 10, 2012, 10:44:52 pm
content: Quote from: ColinB on October 10, 2012, 07:36:41 pmThe entire cal lab room is controlled to a certain temp (22degC IIRC). The small TroSmartCal lab has a big $20K aircon system just dedicated to the lab. Presumably it could handle a room full of people.Calibrationadjustmentof a multimeter is a lot more tedious than a calibration check.Just for the calibration check, if you want the report, they have told me it takes about an hour all up for a typical meter.Dave.

author: nukie
author_rank: Frequent Contributor
timestamp: October 10, 2012, 11:01:59 pm
content: A couple of Geller svr maybe perhaps a few LM399 in parallel is low cost for a calibration check for most DMM. Add a few vishay Z foils resistors then you have a little set of fun. Calibration adjustment is not something anyone can do, it takes an experienced personnel who understands the characteristic of the reference or calibration equipment. Calibration check party is more realistic.

author: billclay
author_rank: Regular Contributor
timestamp: October 12, 2012, 07:59:09 pm
content: Bob Smither did this on the volt-nuts mailing list. Take a look at his Traveling Standard (image below) here:http://www.c-c-i.com/ts

author: PA4TIM
author_rank: Super Contributor
timestamp: October 15, 2012, 07:49:05 am
content: Bobs Idea is great, i believe he had allready 5 man that tested it bit he will need a lot more to avarage it out,Made some references my self. For a 4.5 digit meter just buy a good reference like a LT1027 or LM399. Le it run a few thausant hours and find someone with 6,5 digit or more meter. Do not make t adjustable. It oes not have to be 5.000,000V if it ís 4.953,673 V it is OK, as long as you know it is, and if you do not make it adjustable it will be more stable.I have my own private calibration lab, i collect that kind of gear. Upto 5,5 digit is now problem, i think I can do 6,5 digits within the specs but the biggest problem there is temperature. I have no climate control.Calibration itself is just checking all ranges and noting the result. But to get good result the meter has to be powered on for al least 1hour for a 5,5 digit, 2 hours for 6,5 digit, a day for 7,5 at constant temp, but 4,5 and lower do not matter much.Calibration including adjustment is a whole different story. I need about one hour fore something simple as a Fluke 8000. A HP 5,5 digit (34xx 19" model, forgot the number) or a Fluke 8500 takes many hours. A Keithley 199 or Solartron 7061 software calibration takes me 1 to 2 hours but they can be done partial, so for instance only VDC.I can do VDC from 1uV to 1000V, AC from 1uV to 1000Vrms but only 50Hz and 400Hz.AC and DC current 1uA upto 10A, Resistance 1 Ohm to 1 MFrequency ( 10MHz thunderbolt, 5MHz, 1MHz, 100KHz HP) and a Timebase marker generator50 Ohm scope amplitude calibrator, sinewave scope amplitude calibratorNot calibrators but because of the accuracy and some standards as check I can easy calibrate the average non-labgrade LCR meters (so not things like 4 wire HP or GenArad) this i more like stated early here, comparing a less instrument with a much better one, so if my C meter should be way off in the 1 pF range it will be in de order of maybe 10 fF's, most digital lcr meters gave xx.xx pF on there screen but most times the last 3 digits are just for show under 10 pF and forget about nH, most have poblems under 1 uH. ( I know, I'm talking bullshit, your el cheapo ebay special is correct to the last digit because the 5% 100 uH coil from Farnell was 100 uH at your meter and your foodstore specal multimeter is correct because a 9V battery showed 9.00V >:-) )I can do:Capacitance from a fF to 10 uFSelfinductance from 200 pH to several H.I have this gear from Fluke, Philips, Tek, ESI, GR.So if you do not mind the distance, your welcome. One problem, because the amount of gear there is room for 2 persons to sit, or 3 persons if 2 do not mind standing but then I have troubles reaching my gear.But how great the idea is, and nove to meet people with the same intrests, do not expect much of it. If you only do some basic checks, like some Volt and current ranges. Like you set up 10VDC and there are 10 meters, you plug them in one after the other and note the reading for each you can do a lot in a day, but if you have to adjust then first look in the manual, you will see it is often a lot of work. Most times with older or more high end stuff you need to check a lot more as the ranges. Some things need replacing resistors for adjustment, searing for the calibration points often takes a lot of time ( even reaching some because there is f.i. a 10 turn potentiometer 2 cm under a hole in a shield and the hole is so small you can not look in it and put a trimmer in it at the same time )

author: Smokey
author_rank: Super Contributor
timestamp: January 26, 2016, 04:18:46 am
content: Hey look... New categories for the forum. Move my old thread too! I should change the title to Metrology Party!