Re: You assume that the scales and thermometers are accurate.
" You assume that the scales and thermometers are accurate. "
You might. But that makes you ill informed, a fool, a bad engineer/scientist, or some combination thereof.
Sensible organisations which are taking measurements that matter will take them using tools that have a regular and auditable calibration programme traceable (directly or indirectly) to national and international approved standards. Uncalibrated (or out of calibration programme) instruments and sensors are not appropriate for definitive use. That applies whether you're measuring length, mass, current, voltage, temperature, or any other sensibly measurable quantity.
Readers might wish to look up the history of the subject of "metrology". It goes back a long way, but the SI system of weights measures etc brought it increased prominence in most parts of the world (with one obvious exception), though in fairness it wasn't always called metrology.
For further light entertainment, readers might also want to look up the history of incidents with the Therac-25 to see what can happen when naive people combine hardware, software, and a lack of understanding of the importance of proper closed loop calibration. People died. See e.g.
http://sunnyday.mit.edu/papers/therac.pdf (full version, 49 pages)
Then think about your self driving cars, and why their requirements are different from VCRs.