Introduction to metrology sources - Page 1
Forum section: electronics / general

author: ddr_controller
author_rank: Contributor
timestamp: February 09, 2023, 04:54:34 pm
content: I just found out about this fascinating world of metrology and really want to get into it, but I see it kind of a steep wall as I can't find any good introduction for it.What are some good resources to get into this field?

author: Grandchuck
author_rank: Super Contributor
timestamp: February 09, 2023, 05:28:40 pm
content: It is a steep climb, but never boring. Google will help. I just turned this up:https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=929127

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: February 09, 2023, 05:39:45 pm
content: The early edition of Fluke's book is available as a pdf-http://www.introni.it/pdf/Fluke%20-%20Calibration%20Philosophy%20in%20practice.pdfThe later edition is better if you can find a used copy or are willing to pay the price for a new one.A great collection of early information, still good today, is the National Bureau of Standards (now NIST) Special Publication 300.https://nvlpubs.nist.gov/nistpubs/Legacy/SP/nbsspecialpublication300v3.pdf

author: DH7DN
author_rank: Regular Contributor
timestamp: February 09, 2023, 08:12:58 pm
content: This may sound a little bit arrogant but a measurement is pretty much useless without a stated uncertaintyI am really missing one essential part inside of EEVBlog Metrology forum discussions: dealing with measurement uncertainties and properly estimating them.While all the PPMs are fascinating and Tempcos are important (and are an integral part of an uncertainty budget), not many forum members seem to care about measurement uncertainties when reporting measurement results. Another important part of Metrology is the traceability and there are maybe two/three forum members which take this seriously. Nevertheless, it's a science of its own with many layers of understanding. That's why we're amateurs and love this disciplineThere are two/maybe three "dry" publications which are difficult to read but I would consider them as very important:https://www.bipm.org/en/committees/jc/jcgm/publicationsJCGM 200-2012: International Vocabulary of Metrology - Basic and general concepts and associated terms (2012)JCGM 100:2008(E): Evaluation of measurement data (2008), Guide to the expression of uncertainty in measurement (GUM)EA-4/02 M: Same as GUMhttps://european-accreditation.org/publications/ea-4-02-m/Richard Hogan's Blog at isobudgets.org:https://www.isobudgets.com/blog/Cal Lab Magazine:https://www.callabmag.com/Conrad Hoffman's Homepage:http://conradhoffman.com/mini_metro_lab.htmlNational Metrology Institutes (NIST, PTB, INMETRO, METAS, ...) have some "hidden" resources and publications which can be useful -> googleBesides that, there should be a plenty of free resources (PDF files, presentations, videos) on the Internet. I'm really missing Metrology-related content on Dave's YouTube channel such as Video #1039

author: bdunham7
author_rank: Super Contributor
timestamp: February 09, 2023, 08:43:06 pm
content: Quote from: DH7DN on February 09, 2023, 08:12:58 pmThe thing about uncertainties is that they are.....uncertain. I don't think they necessarily need to be stated, they can be tacitly understood as well. The discussion is certainly worthwhile but I don't agree that the subject is 'missing' from the forum. And to be nitpicky (this is the right place for that after all) a statement of uncertainty is itself incomplete unless it includes a distribution or confidence interval and perhaps the possible modes and causes of the uncertainty.

author: mendip_discovery
author_rank: Super Contributor
timestamp: February 10, 2023, 06:00:02 pm
content: I have tried to talk uncertainties before and willing to explore stuff if people want.I do find it interesting when people talk about a change of 0.5ppm on a measured source but without a UoM it's hard to know if we are just looking at the error of the meter used to measure it.99% of the time labs work to a k=2 aka 95% probability.I'm working on some UoM stuff for a new meter at work so might publish some of that if it just helps others get a basic idea of UoM.

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: February 10, 2023, 06:28:48 pm
content: There have been discussions about uncertainty here in the past. Unfortunately, people who understand it quickly lose me with the math. Somebody needs to write "Uncertainty for Dummies" so I can actually calculate something!

author: mendip_discovery
author_rank: Super Contributor
timestamp: February 10, 2023, 06:54:14 pm
content: Quote from: Conrad Hoffman on February 10, 2023, 06:28:48 pmI find that hard to believe. But yes it is a little math heavy and I will admit I don't quite get all the bathtub statistic stuff as I never studied it. I think the bit that puts people off it is the inconsistency on studies on how its reported and some just posting the rather scary formula and just assuming you know how it all works.It can't be as bad as the smoke and mirrors that is electrical components. You can't use a MOSFET without using a single dangler as that might shift the wotsit by 1/2 an artichoke and you won't get any sense out of what you are doing.

author: mendip_discovery
author_rank: Super Contributor
timestamp: February 10, 2023, 08:04:55 pm
content: Getting back to the subject, you might find this article interesting.The Effect of Cables and Shields on Traceabilityhttps://www.callabmag.com/wp-content/uploads/2014/05/apr14.pdf#page=18For myself, I found this good when explaining some of the types of inputs needed for uncertainty calculations.Probability Distributions and Divisors for Estimating Measurement Uncertainty.https://www.callabmag.com/wp-content/uploads/2016/02/jan16_web.pdf#page=24

author: alm
author_rank: Super Contributor
timestamp: February 10, 2023, 08:10:23 pm
content: What might help with uncertainties is to read a physics or statistics text about error propagation. If I measure a current through a 100 Ohm +/ 1 Ohm (rectangular distribution) resistor as being 100 mV +/ 0.1 mV (two sigma), what's the uncertainty of the current measurement?GUM will tell you how to calculate the uncertainty of each value (like how to convert a rectangular distribution to a standard error), and error propagation tells you how to calculate the uncertainty of the current from the uncertainty in voltage and resistance. This involves some simple partial derivatives, but since the operations in LF metrology don't usually go beyond basic arithmetic, you can get by with rules for the basic arithmetic operations. For examplethis article up to and including "multiplication or division". In the end it's just sums of squares and divisions.

author: Rax
author_rank: Super Contributor
timestamp: February 15, 2023, 03:55:10 am
content: Interesting topic... I was hoping it'd get brought up! And if I'm incredibly lucky I'll finally get an inkling of what uncertainty means and how it's important for my humble world of metrology...

author: Rax
author_rank: Super Contributor
timestamp: February 15, 2023, 04:33:32 am
content: Quote from: mendip_discovery on February 10, 2023, 06:00:02 pmTo my unsophisticated mind, uncertainty is a way to account for the inexactitude of a measurement as based on both the UUT and the measuring instrument compounded inaccuracies. A few hundred words around just this one concept in the metrology world, but I think it's very important to make this comprehensible while not entirely missing its meaning.Assuming that's even remotely correct, how would that translate in the case of the quoted statement. In saying that, I'm simply trying to gauge the relevance of uncertainty for day to day hobby metrology statements and facts. "I measured my 10V source with my 6.5 digit meter that has an unexpired calibration sticker." Not sure how to fit UoM (a new acronym to me! a good day) in that.Not trying to trivialize the topic, just being humble in trying to digest it.

author: pqass
author_rank: Super Contributor
timestamp: February 15, 2023, 06:17:59 am
content: See the following for an accessible read on uncertainty. I didn't see it mentioned earlier in this thread.I don't remember where I found it; could've been in this forum. I've been meaning to re-read it since it's kind of foundational for understanding metrology. I hope it helps.https://www.npl.co.uk/special-pages/guides/gpg11_uncertainty

author: mendip_discovery
author_rank: Super Contributor
timestamp: February 15, 2023, 05:42:15 pm
content: Quote from: pqass on February 15, 2023, 06:17:59 amI agree that is a fairly easy way to get into the whole rabbit hole of uncertainty. To me it does still seem to be a fairly new part of the whole metrology system and there are discussions constantly going on what you need to have in there and how best to present it etc etc.