BS EN ISO 12836:2015 pdf download – Dentistry — Digitizing devices for CAD/CAM systems for indirect dental restorations — Test methods for assessing accuracy.
3.15 systematic error mean that would result from an infinite number of measurements of the same measurand carried out under repeatable conditions minus a true value of the measurand Note 1 to entry: Systematic error is equal to error of measurement minus random error. Note 2 to entry: Systematic error may be constant or proportional to the value of the measurand. Note 3 to entry: In practice, systematic error is estimated from 20 or more repeated measurements of a measurand under specified conditions. 3.16 true value of a quantity value consistent with the definition of a given particular quantity Note 1 to entry: This is a value that would be obtained by a perfect measurement. True values are, by nature, indeterminate. Note 2 to entry: The indefinite article “a”, rather than the definite article “the”, is used in conjunction with “true value” because there may be many values consistent with the definition of a given particular quantity. Note 3 to entry: A reference data set obtained by the procedures of A.4.2 or B.4.2 is used as a true value in A.6.2 or B.6.2. Dimensions described in C.4 are used as a true value in C.6.2. Note 4 to entry: The magnitude of an angle or a dimension of a test object described in A.4.1 or B.4.1 obtained by an independent method of measurement may be taken as a true value, provided that the object has been manufactured in a process qualified and calibrated to the precision specified in A.4.1 or B.4.1. 3.17 trueness closeness of agreement between the mean obtained from repeated measurements and a true value or a conventional true value Note 1 to entry: Trueness is a qualitative concept. The operational definition that applies for this International Standard is given in 5.3.3. [SOURCE: ISO 5725-1:1994, 3.7, modified]
5 Test methods 5.1 General Use at least two of the test methods described in Annex A, Annex B, and Annex C. 5.2 Test conditions Testing shall be done under the following test conditions: a) the change of temperature during the test shall remain within ±1 °C; b) the ambient room temperature shall be (23 ± 2) °C in accordance with ISO 554; c) the quality of the data set in terms of any missing or corrupted data shall be evaluated by the operator; in cases of missing or corrupted data, the test shall be repeated. 5.3 Accuracy 5.3.1 Repeatability Repeat the measurement 30 times without removing the test specimen from the digitizing device. Use the test specimen and procedures specified in Annex A, Annex B, or Annex C as recommended in the manufacturer’s instructions for use. Calculate the mean and standard deviation of the 30 measurements. Record this value(s). 5.3.2 Reproducibility Repeat the measurement 30 times, removing the test specimen from the digitizing device and replacing it into the digitizing device. Use the test specimen and procedures specified in Annex A, Annex B, or Annex C as recommended in the manufacturer’s instructions for use. Calculate the mean and standard deviation of the 30 measurements. Record this value(s). 5.3.3 Trueness Calculate the difference between the mean of the 30 repeatability measurements and a true value obtained independently according to the respective annex. (See A.6.2, B.6.2, or C.6.2).