M for Metrology and metrologist
07. 08. 2024
The Metre Convention (also known as the Treaty on the Metre) is a diplomatic agreement and is the umbrella document in the field of metrology. It was signed on 20 May 1875 by representatives of 17 countries with the aim of establishing an international organisation for weights and measures (BIPM). Slovenia (my home country) was then still part of the Austro-Hungarian Empire, and was one of the first 17 signatories to the Convention. It is worth mentioning that in 1777, almost 100 years earlier, the Austro-Hungarian Empire already had a legislative framework governing metrology, which made it obligatory to legal verify a certain type of measure, one of the first documents of this kind in the world. The 20th of May is still celebrated today as International Metrology Day. Slovenians are particularly proud that on the same day we also celebrate International Bee Day. Slovenia played a key role in the proposal and adoption of Bee Day and is one of the beekeeping superpowers.
The Metre Convention covers, among other things, the basic units of measurement, initially including only the unit of length, the metre, and the unit of mass, the kilogram. Only later, in 1921, were other physical units added. Major revisions to the units of measurement took place in 1960 and 2018. Today, there are seven basic units of measurement, which are grouped together in the so-called International System of Units (abbreviated as “SI”). The evolution of units of measurement is important because the constant evolution of technology requires the evolution of units of measurement, and of metrology as such.
But today I would like to focus more on metrologists, because everyone can read a lot about metrology on the internet. A metrologist is a person who makes measurements, who deals with metrology. A person who operates measuring instruments. A person who must know the laws of metrology. Must be familiar with unit converters, if you like. The result of the measurement depends on the metrologist. The result of a measurement is by no means a number displayed by the measuring instrument, but much more. It involves corrections for influential parameters such as the environmental conditions in which the measurement is made. Take the example of measuring an aluminium engine block. We can quickly see that the temperature of the block itself is an important parameter that affects the accuracy (and measurement uncertainty) of the measurement. If, for example, the block has a dimension of 500 mm and the measurement is taken at 23 °C, the elongation of the material (and of the gauge itself) will yield somewhere around 20 μm (micrometres) or 0.02 mm (millimetres). If the tolerance for the engine block is 5 μm, this is an elongation four times greater than the tolerance and we must make a correction as a matter of urgency – we must consider the elongation of the block. It is not only important how we measure the length, but much more important how we measure the temperature of the block. Without laboratory (‘climate-controlled’) conditions, this will be mission impossible.
What should the climate be like, how long do we need to keep the block in the room itself to adjust to the temperature. How will the gauge be expanded. The basic principle of “good enough” must always be followed. How good a thermometer we have. How to prepare the surface of the block to make the measurement possible, to make it meaningful at all. All so that the result is given properly, accurately, correctly, whatever you want to call it. And to give the result at the reference temperature, which in this case is 20 °C. Why is this important? So that the measurement in Slovenia is comparable to that in Germany, France or anywhere else in the world. A metrologist needs to know all this and more. He must be aware of all this and take it into account in order to give a proper measurement. Otherwise, you can imagine the chaos, the misunderstandings that would arise. And that was roughly the situation before the Metre Convention came into force. Practically every region had its own units of measurement. And that is not all. Every new ruler who came to power introduced his own units (he wanted to be important, the most important, because he is the ruler). No telephone, no World Wide Web, last but not least no newspapers, no radio, no television. I really wonder how that worked, it was a mess.
There is hardly a product nowadays that is not linked to measurement in one way or another. Endless amounts of measurements are used today in manufacturing, research and other processes. Whatever you use on a daily basis, from the grocery store, the petrol station, the pharmacy, all the way to jewellery, food, water, air. Everything is subject to measurement. Everything. And we all expect the measurements behind these products to be accurate, reliable. Without a second thought. In fact, that’s what we demand anyway. Do you ever wonder what is behind it all? What all has to be regulated, prescribed, specified … to make it all work. And what all the metrologist has to consider in his work in order to meet our demand (expectation). What burden is on the metrologist?
It is therefore essential that a metrologist has certain personal qualities in addition to measurement knowledge and skills. Focus, patience, consistency and honesty. These are qualities, as well as knowledge and skills in metrology, that as a person you do not get in the education system. Almost none of this is taught in our general or vocational education. Secondary education does not, in fact, contain these skills. With a few exceptions, and even these to a very limited extent, even after secondary education, you cannot acquire these skills at university. Unfortunately, this is not in the curricula. Despite the fact that we are talking about so-called horizontal skills, which are needed by all sectors, all industries, most research institutions, most of the public sector. You could say that everybody comes across metrology at some time or another. There has been a lot of talk lately about digital literacy. Maybe it is about time we started talking about metrology literacy.
Focus is the quality of being concentrated on a specific thing. To be focused is to direct all your attention to the point. And that’s what a metrologist has to be – focused on his task, on his measurement. The measurement that he is currently making, in order to eliminate or at least minimise the risks of mismeasurement as much as possible. There are risks in every measurement, because every measurement is subject to doubt. We can hardly expect to make a good measurement if our minds are elsewhere. All too quickly, errors occur that spoil the measurement. We must not allow this to happen, because most of the measurements we make are made for someone else. Someone who will rely on those measurements. Someone who trusts those measurements and builds their own process on them. And if we get it wrong somewhere in the process, it will affect the product for the rest of its life. Do we want to use such a product?
Patience is the quality of being focused all the time, all the way. And some measurements can take a long time. And focus has to last all the time. This is why digitalisation and automation are increasingly being used in metrology, even though some measurements are still entirely manual. There are some measurements where the metrologist has to have a lot of patience. Often even before the measurement itself, for example when preparing the sample to be measured. Imagine aligning a measuring ring on a floating table. The operator has to turn the ring repeatedly and very patiently to ensure that the ring is actually aligned perpendicular and in the correct measurement plane. The required or rather expected accuracies in this procedure are at the micrometre level (one thousandth of a millimetre). Let me just mention that the average thickness of a human hair is somewhere around 50 micrometres.
Consistency is a quality where a person always follows certain principles, procedures, tasks. Even though a metrologist may make dozens or hundreds of identical measurements, he must always follow the prescribed procedure in every detail, without exception. The procedures are prescribed in order to be comparable with each other. So that measurements do not have to be duplicated. Because just imagine if every customer took his own measurements. Pointless, expensive and often unrealistic. Often with metrologists we talk about fatigue, about rigidity, about getting bored because they repeat the same measurements. Simply, there is no room for these things in measurement.
Honesty is a quality where a person does not take advantage of and thereby harm another. As a metrologist makes measurements mostly for others, this is the basis. The result must be accurate, and that means honest. Under no circumstances should we give in to pressure from the client or anyone else. On the one hand, the metrologist must be focused, consistent and patient, which are all qualities linked to passion, to emotion, while on the other hand he must be honest, which means he must be cool, he must be like a robot, without emotion.
I am more and more convinced that metrology is to a large extent psychology, and laboratories should train their metrologists in this direction. Towards psychological toughness and determination, but on the other hand humility and a desire to learn, to know more. Responsibility. Just taking full responsibility.
Primoz
Next time, 21 Avgust 2024, Impartiality