Accuracy vs Repeatability
Accuracy of a temperature measurement system is the degree of closeness of the measurement of a temperature to that temperature's actual (true) value.
Repeatability of a measurement system, also called precision, is the degree to which repeated measurements under unchanged conditions show the same results.
As an example, an instrument could present the same value for temperature every time (under the same measurement conditions) but the value is offset from the correct value. This is repeatable but not accurate. The ideal measurement therefore would be both accurate and repeatable.
For those familiar with target shooting, a marksman could tightly cluster his shots on the target (repeat-able) but the cluster may not be in the bull's - eye. Accuracy on the other hand is the ideal situation to have all the shots closely clustered in the bull's - eye. This result is both accurate and repeatable. See below figure.
Repeatability of a measurement system, also called precision, is the degree to which repeated measurements under unchanged conditions show the same results.
As an example, an instrument could present the same value for temperature every time (under the same measurement conditions) but the value is offset from the correct value. This is repeatable but not accurate. The ideal measurement therefore would be both accurate and repeatable.
For those familiar with target shooting, a marksman could tightly cluster his shots on the target (repeat-able) but the cluster may not be in the bull's - eye. Accuracy on the other hand is the ideal situation to have all the shots closely clustered in the bull's - eye. This result is both accurate and repeatable. See below figure.
Date Published: March 6, 2019
Source: The Engineer's Guide to Industrial Temperature Measurement - 2013 Edition
Source: The Engineer's Guide to Industrial Temperature Measurement - 2013 Edition