Metrology, why care?  - Page 1
Forum section: electronics / general

author: BarrowBoy
author_rank: Contributor
timestamp: July 15, 2024, 03:53:58 pm
content: Metrology, why care?How do you know what you measuring without it? , how do you know what your paying for without it? How can we advance as a civilization without it? And Metrology is not Calibration they are often confused.Impedance & Capacitance...did you know the SI unit for these is supported by Australia's NMI, and accepted by BPIM in Paris.Metrology allows improvements in measurement, that eventually leads to a updated SI being realized. It's a never ending chase to true accuracy. We will never know the actual, just our best "educated guess". As the saying goes "The only certainty is there is uncertainty" !!

author: mendip_discovery
author_rank: Super Contributor
timestamp: July 15, 2024, 05:12:40 pm
content: QuoteBecause it is an integral part of our life.QuoteI agree, even calibration has been wrongly misrepresented over the years. This I partly put down to metrology and calibration still being quite a new thing and we are learning more about them as we get better at doing them. Take gauge blocks, they are 128 years old but since then we have learnt more about temperature coefficients and that in turn has influenced uncertainties, computers can do more maths on the fly and this means repeatability and accuracy.The problem is the more you look into metrology the more you realise you don't know much about it. It is like a mandelbrot image.EDIT: From what I am hearing the NMI are no longer the holders of the best realisation of SI units.

author: BarrowBoy
author_rank: Contributor
timestamp: July 15, 2024, 06:04:09 pm
content: metrology and calibration have been around since the dawn of man, but agree with your sentiment, there is no checkered flag to take. In Egyptian times, workers lost their arms if they did not follow best practices, it's how they ended up with such repeatability of measurement. How they got those slabs up the top?And you mention temperature scales...good point (parden the pun), but did you know in early times the temperature scale was inverted. Boiling water was the reference point, rather than the freezing point. Any idea why they changed it. Working in a Calibration lab, and being a nerd I think you might just know

author: TimFox
author_rank: Super Contributor
timestamp: July 15, 2024, 06:13:47 pm
content: The only temperature scale of which I am aware that assigned a higher numerical value to freezing than to boiling was Anders Celsius' original scale that set 00at the boiling point of water and 100oat the freezing point. It was invented in 1742.The Fahrenheit scale (32 to 212 for freezing and boiling) was invented in 1724.The Réaumur scale (0 to 80) was invented in 1730.The Centigrade scale (0 to 100) was invented in 1744, and was renamed Celsius in 1948 to avoid confusion with other meanings of "grade", inverting Celsius' original scale.When I turned 32 (many years ago), I started to convert my age to Celsius.A few years later, I started to convert it to Réaumur.Eventually, I switched to radians.

author: mendip_discovery
author_rank: Super Contributor
timestamp: July 15, 2024, 06:41:29 pm
content: Quote from: BarrowBoy on July 15, 2024, 06:04:09 pmIt has been around for ages but our understanding of it I would say is fairly modern. I wonder if it is a bit like Moore's law. I wonder if we will ever get 9.5-digit multimeters.I tried a few years ago to get some dim stuff on the schedule and I fell into a moment where there was a realisation that if measuring a micrometer you needed to have uncertainties for all measurements, normally in the past you had an uncertainty for the length but all of a sudden it was expected you had one for flatness, parallelism, etc. I managed to get 80% of the way into getting the stuff on the schedule but it was decided that I was needed onsite so it got dropped. It is just a sign we are always working towards better things. I am not a fan of the dim stuff as there are lots of contributions and the human element is always there and a large source of issues.Quote from: BarrowBoy on July 15, 2024, 06:04:09 pmThe two points they had for thermometers were the Boiling point and the Freezing point of water, so they used 0 as boiling points and counted down to 100, avoiding negative numbers.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7120475/

author: TimFox
author_rank: Super Contributor
timestamp: July 15, 2024, 06:52:24 pm
content: For "they", you mean "Anders Celsius", influenced by De Lisle.Fahrenheit and Réaumur predate Celsius.Fahrenheit used different reference end-points, and this historical matter is somewhat controversial.Non-US residents scoff at Fahrenheit, but his range of 0 to 100 is a reasonable ambient temperature range for human health and comfort.Therefore, although as a physicist I use Celsius and Kelvin for technical purposes (such as semiconductor junction temperature), I use Fahrenheit to determine what sweater to wear.

author: tggzzz
author_rank: Super Contributor
timestamp: July 15, 2024, 07:17:19 pm
content: Quote from: TimFox on July 15, 2024, 06:13:47 pmI might try that, but I'm concerned about two points:whether people who know me would recognise that I had changed to radianswhether websites would allow me to enter the fractional partOne alternative would be to state your age in base 13. Has the advantage that 6 times 9is42.

author: jjoonathan
author_rank: Frequent Contributor
timestamp: July 15, 2024, 07:46:38 pm
content: Because whoever dies with the most digits wins.Duh.

author: artag
author_rank: Super Contributor
timestamp: July 15, 2024, 07:54:02 pm
content: Because it's there

author: AnalogTodd
author_rank: Regular Contributor
timestamp: July 16, 2024, 01:22:51 pm
content: Quote from: tggzzz on July 15, 2024, 07:17:19 pmEvery true nerd should get that reference...

author: CatalinaWOW
author_rank: Super Contributor
timestamp: July 16, 2024, 03:04:53 pm
content: There are two reasons for metrology. Many of the comments on this thread allude to the pursuit of knowledge for knowledges sake. That is fine. In my opinion is the driver for many volt and time nuts activitiesThe other is to make the activities of our lives fairer, more effective, cheaper and more reliable. Known weights allow both bluey and seller to be sure of their bargains. In this application needed accuracy was achieved hundreds of years ago. Then, as we learned more real chemistry greater accuracy was required.Gauge blocks were a step in the whole interchangeable parts progression. Watt famously required a tight fit between the piston and cylinder of his steam engines. So tight that you could not fit a shilling into the gap. Starting in the 1700s the ability to get partsfrom various sources and assemble them into a working mechanism began to spread. Gasoline engines at the turn of the twentieth century needed tighter fits and gauge blocks assisted in achieving this economically. But into the mid century critical parts like connecting rods to crankshaft were measured and shimmed to desired fit. Advances in measurement accuracy allowed these parts to be manufactured so this step was no longer necessary.I believe this the real driver of metrology.

author: TimFox
author_rank: Super Contributor
timestamp: July 16, 2024, 04:01:03 pm
content: Quote from: mendip_discovery on July 15, 2024, 06:41:29 pmAvoiding negative numbers is not correct. The Ancients knew that the melting points of common metals (lead, copper, gold, iron, etc.) were "hotter" than the boiling point of water, so in Celsius' original scale they would be negative numerical values.

author: mendip_discovery
author_rank: Super Contributor
timestamp: July 16, 2024, 04:31:05 pm
content: Quote from: TimFox on July 16, 2024, 04:01:03 pmSorry but according to the  National Library of Medicine via the link I already posted,https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7120475/Quote

author: TimFox
author_rank: Super Contributor
timestamp: July 16, 2024, 08:13:03 pm
content: How did putting zero at boiling avoid negative numbers over the range of temperatures encountered in normal applications?Cooking: hot oil is used at above 200oC for frying.The syrup temperature for candy making is around 160oC.Was frying invented after Celsius?The statement about negative numbers in your reference is not supported in that article, and is merely supposition.(I admit that in Uppsala, where Celsius lived, the winter temperature went far below freezing.)To avoid negative values, one must use absolute temperature (Kelvin or Rankine), which was first introduced around 1702.Celsius made the important observation that the freezing point was relatively insensitive to atmospheric pressure, but the boiling point was a function of pressure: therefore, his scale's zero shifted with atmospheric pressure.Linnaeus, the other great Swedish scientist of that era, inverted Celsius' scale for his use in greenhouses.The Wikipedia articlehttps://en.wikipedia.org/wiki/Thermodynamic_temperature#Historyon thermodynamic temperature has a more cogent discussion of the history of thermometer scales, although it ignores Réaumur.Nobody seems to have defined an absolute temperature scale for Réaumur, although much of the experimental work on thermodynamics in Germany during the 19th century used Réaumur thermometers.

author: mendip_discovery
author_rank: Super Contributor
timestamp: July 16, 2024, 08:39:15 pm
content: Quote from: TimFox on July 16, 2024, 08:13:03 pmThe true reason for metrology is so we can argue about stuff.Tim, I quoted and highlighted the very statement that is from the National Library of Medicine, not Wikipedia."reversed scale with increasing numbers for decreasing temperatures, which avoided having negative values."Much like how AWG gets a lower number the bigger the wire gets.These are medical thermometers so these were not for measuring cooking oil or furnace temperatures but for the human body.Right, I am off the internet for a few days, I don't like arguments.

author: TimFox
author_rank: Super Contributor
timestamp: July 16, 2024, 09:41:41 pm
content: For those interested in Celsius' invention:Seehttps://archive.org/details/kungligasvenskav1317kung/page/170/mode/2up?view=theaterwhich is not Wikipedia.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: July 17, 2024, 12:43:39 am
content: All of the argument reminds me of many of the arguments about English/Imperial/US units vs Metric. The ones that talk about the inherent superiority of a unit based on the freezing point and boiling point of water vs other choices. Or the intrinsic superiority of a unit which is (sort of) a simple fraction of the distance from the equator to the pole. Yes I know that all of the units are no longer traced to physical items, but their current definitions are merely precise definitions of an arbitrary dimension or quantity.One of the benefits of metrology is a growing commonality in the language we use to measure things.

author: ITArchitect
author_rank: Contributor
timestamp: July 17, 2024, 12:38:08 pm
content: Right, method to the madness!

author: leighcorrigall
author_rank: Frequent Contributor
timestamp: July 17, 2024, 04:55:37 pm
content: In my area of interest (i.e., analytical chemistry), we accurately measure hydrogen in metals. This is usually done with a mass spectrometer, high-temperature furnace, and vacuum system. Measurements are important for engineering materials that are either directly or indirectly exposed to hydrogen. The ingress of hydrogen into metals can change the mechanical behaviour of materials. Sometimes, hydrogen dissolution can be advantageous when hot-working refractory metals such as titanium by lowering flow stress through a beta-transformation or when producing porous aluminum form for lightweight applications with hydrides. In less desirable examples, hydrogen may limit the service life of a critical component, such as turbomachinery for aircraft, welds in gas pipelines for fuel distribution, and pressure tubes that support nuclear fuel channels. With the emerging hydrogen economy, these problems will become strategically important for adopting this fossil fuel alternative. In fact, hydrides are becoming increasingly important as a solid storage medium.Trace amounts of hydrogen, on the order of parts per million by weight, can significantly change a material. Major factors related to hydrogen affect fracture toughness and elongation, among many other properties. Without knowing exactly how much hydrogen is in a material, it is often difficult to even understand how engineering metals can be impacted.For example, copper, a material being proposed for the long-term containment of spent nuclear fuel, can absorb hydrogen and allow it to migrate through the barrier. Over long periods, that hydrogen ingress (or perhaps egress) can lead to corrosion of structural materials designed as nuclear barriers such as steels. Literature suggests that we have only studied the solubility, permeation, and diffusion of hydrogen in copper at high temperatures (approximately > 450 Celsius) because it is very difficult to measure hydrogen at ambient temperatures. Spent nuclear fuel will remain at 70 to 150 Celsius for centuries, and we have not even measured hydrogen concentrations in copper at these temperatures. All we can do is rely on extrapolations. Imagine the difficulty of accurately measuring hydrogen migration in a container that is expected to last up to 100,000 years without all the empirically measured variables. This lack of information (or a greater reliance on good assumptions) is present in most other areas involving hydrogen.In summary, metrology is important so that scientists can compare results with others to a high level of certainty and also measure hydrogen with incredible accuracy so that we can study real-world phenomena that impact socioeconomic problems that deeply impact our civilizations. Metrology is a hidden giant that binds almost all other quantitative fields of science together. I am studying gravimetry and amperometry, which are the foundations of mass spectrometry: the mass-to-charge ratio and the relative intensity. Chemistry is simply a secondary interest to me.

author: leighcorrigall
author_rank: Frequent Contributor
timestamp: July 18, 2024, 02:47:24 pm
content: Quote from: BarrowBoy on July 15, 2024, 03:53:58 pmThis sounds like Socrates.https://en.wikipedia.org/wiki/I_know_that_I_know_nothing

author: Geoff-AU
author_rank: Frequent Contributor
timestamp: July 18, 2024, 11:38:49 pm
content: Everyone knows the best temperature scale is Kelvin. None of those pesky negative numbers (at least, we'refairlysure....)

author: KE5FX
author_rank: Super Contributor
timestamp: July 19, 2024, 03:54:28 am
content: Technically I believe the laser people consider a population inversion to be a 'negative Kelvin' phenomenon.

author: TimFox
author_rank: Super Contributor
timestamp: July 19, 2024, 04:03:19 pm
content: That inversion is a real effect, but is a generalization of actual thermodynamic temperature using the same math to achieve negative temperature values for non-thermal situations.If you don't like Kelvin, you can always use Rankine.Note that when you measure temperature in Celsius, you use the unitoC.If you are careful, you measure temperature differences in Co.However, you do not need to use the degree symbol when you measure either temperature or difference in Kelvins, "K".Someone who did not understand this wrote a news article about how climate change scientists worry about a 2 Corise in average global temperature.The author put that into a units translation program and called it 35.6oF.I think we can all agree that a rise in global temperature of 35.6 Fo= 20 K would kill us all.

author: binary01
author_rank: Contributor
timestamp: July 28, 2024, 12:43:28 am
content: Quote from: BarrowBoy on July 15, 2024, 03:53:58 pmGiven your location, I'm wondering if you are a member of the Metrology Society of Australasia (MSA)? One of the main aims of the society is to help educate the public about the importance of metrology, how it impacts manufacturing, research, science, fair trade, but also everyday life. It is not an easy task!I still like this VSL (Netherlands) video for helping the general public to understand metrology is more than measuring tapes and vernier calipers:It is hard to explain why we spend our careers trying to reduce uncertainty to grasp the true SI values, fully knowing/hoping that we will only get closer but can never achieve it without uncertainty. But it is strangely addictive and the pursuit makes our work forever interesting. I am grateful for that.Climate change is a good example that's on everyone's radar. We are measuring small changes in temperatures (relative to the uncertainty), year-on-year, and trying to make accurate trend predictions. Measurements are being made independently across all regions of the world with different traceability, but need to be shared and loaded in to a common model. To be useful and trustworthy, this requires very good quailty, low uncertainty metrology!

author: BarrowBoy
author_rank: Contributor
timestamp: July 29, 2024, 05:35:35 am
content: Quote from: binary01 on July 28, 2024, 12:43:28 amHi binary01, Yes well aware of the MSA. Do you ever attend any of the bi-yearly conferences?. Next years will actually be in Sydney, my home town so should be good. Are you involved in international intercomparisons. Nice video, but I think VSL took that idea from Yokogawa Europe, which is another good example of Metrology all around us. Time being the most measured parameter, then I believe volume being the second.Also this is for people looking to get into the industry within Australiahttps://www.chiefscientist.gov.au/GSGstemexpo

author: binary01
author_rank: Contributor
timestamp: July 29, 2024, 07:13:41 am
content: Quote from: BarrowBoy on July 29, 2024, 05:35:35 amYes, I have attended all MSA conferences since I started in metrology in 2009. Last year was in Wellington NZ and next year (starting 25th Aug) it will be in Sydney as you have indicated. I am on the MSA National Committee and can already tell it will be great event in Sydney, so I am looking forward to it, and you should certainly plan to attend given that it is in your city.Quote from: BarrowBoy on July 29, 2024, 05:35:35 amWe participate and coordinate intercomparisons mostly across Australia and New Zealand, but have had some rare opportunities to participate in broader international comparisons. We do informal comparisons against Fluke UK (electrical) and Fluke USA (pressure) as we are cycling reference equipment for calibration, but these are only for our own internal quality assurance.Quote from: BarrowBoy on July 29, 2024, 05:35:35 amDespite this, I believe there are more accredited cal labs covering pressure metrology in Australia than an other area! It probably relates to our extreme reliance on gas and mining in Australia.