Product Regulation and Metrology Bill [Lords]

Chris Vince Excerpts

2nd reading
Tuesday 1st April 2025 Commons Chamber

[Adam Thompson]

I am grateful to the right hon. Gentleman for his intervention, and I am happy to explain. Those particular forms of measurement are not in common use any more, but of course many right hon. and hon. Members of this House will have grown up with them. Broadly, the ones that are still in use are defined in the modern parlance, but it is important to remember that the modern metric system accounts for all of those heritage measurements. The common inch, for example, is formally defined as 25.4 mm, and while I apologise to Members across the House, it is important for me to let them know that the pint is formally defined as 568 ml. Those heritage measurements and, indeed, the entire imperial system are now referenced on to the metric system; defined very simply, the imperial system is the metric system. There is no reason why we should not use those historical measurements—where they are useful, they are perfectly valid—but they are formally defined with reference to the modern metric system. I will talk more about this shortly.

Metrology lies at the heart of everything we know, from telescopes to speed cameras and from knee replacements to jet engines. Every single thing made by human hand was designed first, constructed second and then checked by a metrologist to ensure it met its specifications—if we cannot know it, we cannot improve it. However, ensuring that parts meet their specifications is not simple, as each measurement, dimensional or otherwise, has an associated measurement uncertainty. That is a non-negative parameter characterising the dispersion of the quantity values being attributed to the thing being measured, based on the information used. Estimation of measurement uncertainty is a complex procedure—one that formed much of my career prior to coming to this place—and is usually performed in line with the “Guide to the expression of uncertainty in measurement”.

Uncertainty estimation is generally performed by making measurements that are traceable to the definition of the SI metre—when we are concerned with the metre. Again, the “Vocabulaire international de métrologie” defines traceability as a property of a measurement result whereby the result can be related to a reference through a documented, unbroken chain of calibrations, each contributing to the overall measurement uncertainty. Traceable measurements allow for the successful estimation of uncertainty and are generally a base requirement for the verification of manufactured goods. Traceability is considered by the international community to be the only means by which evidence can be provided towards a given product fulfilling the requirements set out by its designer.

To provide an example, let us consider a length measurement made between two faces of a manufactured part, such as a Rubik’s cube. Imagine that I am holding a Rubik’s cube—I could not possibly have brought a prop, Madam Deputy Speaker. The length between two faces could be measured by a calliper. That calliper would be calibrated using a measurement artifact, most commonly a metal cuboid called a gauge block. That gauge block would in turn be calibrated by a more accurate instrument, which itself is calibrated using a more accurate gauge block. That more accurate gauge block would then be calibrated with reference to an optical interferometer using a laser source. That laser source is finally calibrated against the iodine-stabilised laser that is used to realise the definition of the metre, so traceability is established from the shop floor measurement all the way up to the definition of the metre by an unbroken chain of calibrations.

[Chris Vince (Harlow) (Lab/Co-op)]

It feels impertinent to intervene, because my hon. Friend is giving a hugely passionate speech about a subject he clearly knows so much about, but how can he can help the next generation of metrologists to be as inspired about this topic as he clearly is?

[Adam Thompson]

That is very kind, and I thank my hon. Friend very much for his intervention. If he wishes, I have a 97-slide lecture that I would be more than happy to deliver afterwards.