Feels like a chicken and egg senario. Let’s say I get my torque wrench from work sent off to be calibrated, and that’s calibrated with something itself needs to be calibrated, and so on and so fourth. How’s that figured out?
In: 430
There’s one other complication that I think is still worth mentioning for an ELI5 and that is additive errors. Say you have a standard that is calibrated for a second but you then want to use that to calibrate something that is measuring days. Since there is some uncertainty associated with each second of the standard, then you end up with a greater uncertainty in the day measurement that is calibrated against a lot of seconds. Usually that is still more than good enough.
I ran into this when an idiot Quality Assurance Engineer insisted we calibrate a 300 m steel tape by sending it down to a nuke plant where they could calibrate length, traceable back to official standards. But they couldn’t measure the whole thing at once so had to do it in sections so the uncertainties were greater. We didn’t tell him and just ticked the box. We also didn’t tell him we didn’t correct for thermal expansion or the stretching of the tape as you hung it down a well. But as long as are working tapes were calibrated against that one, we were internally consistent and that was what really mattered.
Feels like a chicken and egg senario. Let’s say I get my torque wrench from work sent off to be calibrated, and that’s calibrated with something itself needs to be calibrated, and so on and so fourth. How’s that figured out?
In: 430
There’s one other complication that I think is still worth mentioning for an ELI5 and that is additive errors. Say you have a standard that is calibrated for a second but you then want to use that to calibrate something that is measuring days. Since there is some uncertainty associated with each second of the standard, then you end up with a greater uncertainty in the day measurement that is calibrated against a lot of seconds. Usually that is still more than good enough.
I ran into this when an idiot Quality Assurance Engineer insisted we calibrate a 300 m steel tape by sending it down to a nuke plant where they could calibrate length, traceable back to official standards. But they couldn’t measure the whole thing at once so had to do it in sections so the uncertainties were greater. We didn’t tell him and just ticked the box. We also didn’t tell him we didn’t correct for thermal expansion or the stretching of the tape as you hung it down a well. But as long as are working tapes were calibrated against that one, we were internally consistent and that was what really mattered.
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