I think it's more a case of consistency of equipment than right or wrong. That's why at the end of this year I will have a 30 year record in Penzance, using the same equipment. In the case of temperature sheathed thermometers in a wooden screen. I've not even changed to a plastic screen, I can't believe it behaves in exactly the same way as a wooden one (which I paint each year).
I've calibrated my receiver so the electronic thermometer in the screen (I've got a couple of others around the garden, the front garden is frequently colder in winter, it collects cold air when it's still.) so it agrees with the sheathed thermometers under stable conditions. Under rapidly changing conditions they are frequently 0.3C or so different.
When I see these very precise (as opposed to very accurate) figures quoted for global warming (of which there is no doubt) I do wonder how they can claim to be so accurate considering all the instrument & location changes. As for a traditional rain gauge & a TBR!
I help out with the COL returns sometimes, and I get some very precise figures, sometimes to 3 decimal points for mean temperature, 2 decimal points for mean wind speed.
Penzance - Glorious start - no ground frost this morning, minimum 1.8C late yesterday evening, lowest of the autumn/winter so far. Overnight shower dropped 0.3mm