CMM Check Measurement Report

[[To...]]

I just got my first look at the measurement report generated on a CMM Check artifact. The CTE values are listed as ppm/K. Just curious why they would introduce another temperature scale. I assume this is "parts per micron per degree K" or could it be "parts per million per degree K"? When I see ppm, I think of the latter.

[[De...]]

Kelvin and Celsius degrees are exactly the same amount, they just start at different points along the temperature scale.

So 0 degree Celsius = 273.15 degree Kelvin and 1 degree Celsius = 274.15 degree Kelvin

ppm in this case most likely is 'parts per million' which if in the metric scale is microns per meter

So essentially ppm/k is the same as μ/m per degree C

Why they would have done this is questionable, the reasoning is likely that scientists like to us ppm/K for CTE values however that rationale seems a bit weak to me since it does not match the labels in Calypso.

Either way, the labels may be different, the function however is identical.

[[Th...]]

I don't have access to a copy of ISO 10360, but the small informative bit ISO let me read online out of 10360-12 says that expressing temperature as Kelvin is just as acceptable as Celsius. Ppm is parts per million in this case as well.

It's weird, they shifted the temperature expression over to an SI unit, but then at the same time they shifted the length expression away from SI? As far as I can tell μ/m is the proper way.