To expand on this, the thermometer itself will come with documentation tracing its calibration back to NIST. This applies to scientific instruments of all kinds

To expand on this, the thermometer itself will come with documentation tracing its calibration back to NIST. This applies to scientific instruments of all kinds. Not doing that is part of why grocery store thermometers are so cheap. https://www.nist.gov/traceability/supplementary-materials-related-nist-policy-metrological-traceability https://www.nist.gov/traceability/supplementary-materials-re...