1 Accuracy of measurement

The consistency between the measured result and the measured true value.

Note 1: Accuracy is a qualitative concept.

Note 2: The term precision cannot be used as a synonym for "accuracy".

Note 3: The absolute true value cannot be known, and can usually be replaced by the recognized true value or acceptable reference value.

Note 4: Measurement "error" refers to the difference between the measurement result and the true value of the measured object.

Note 5: "Random error" refers to the difference between the measurement results and the average value of the results obtained by infinitely many measurements of the same quantity under repeated conditions.

Note 6: "System error" refers to the difference between the average value of the results obtained by infinitely many measurements of the same quantity and the true value of the quantity under repeated conditions. The system error of measuring instrument (such as gas analysis system) itself is called "deviation".

Note 7: Random error is equal to error minus system error.

2 Repeatability

Under the same measurement conditions, the consistency between the results of multiple consecutive measurements of the same measured object.

Note l: These conditions are referred to as "repeatability conditions".

Note 2: Repeatability conditions include:

——The same measurement procedure;

——The same observer (operator);

——The same measuring instrument (gas analysis system);

——Same location;

——Repeat the measurement in a short time.

Note 3: Repeatability can be expressed quantitatively by dispersion characteristics of results.

3 Reproducibility

The consistency between the same measured results under the changed measurement conditions.

Note 1: When giving the reproducibility, the changed conditions shall be clarified.

Note 2: The changed conditions may include:

——Different measurement methods or/and measurement principles;

——Different observers (operators);

——Different measuring instruments (gas analysis system);

——Different reference materials;

——Different locations;

Note 3: The reproducibility can be expressed by the variance of the measurement results.

4 Verification

The identification that the specified requirements have been met through the objective evidence provided.

Note l: In design and development, verification focuses on the process of inspecting the results of an activity to ensure that the activity meets the specified requirements.

Note 2: The term "verified" is used to indicate the corresponding status.

Note 3: In gas composition analysis, validation refers to the consistency between a single result and the result determined by an independent method.

5 Confirm validation

The identification that the requirements for specific intended use or application have been met through the objective evidence provided.

Note: In gas composition analysis, confirmation refers to the confirmation that the method used is suitable for the intended ear.

6 Uncertainty of measurement

Characterize the parameters that are reasonably assigned to the dispersion of the measured value and are associated with the measurement results.

Note 1: This parameter can be the standard deviation or its multiple, or the half width of the interval indicating the confidence level.

Note 2: Measurement uncertainty usually consists of multiple components. Some of these components can be estimated from the statistical distribution of the measurement column results and characterized by the experimental standard deviation. Other components can be estimated based on the assumed probability distribution of experience or other information, and can also be characterized by experimental standard deviation.

Note 3: The measurement results should be understood as * * * good estimates of the measured values. All uncertainty components contribute to the dispersion, including those caused by systematic effects (such as those related to correction values and reference standards).

6.1 Standard uncertainty

Uncertainty of measurement results expressed in standard deviation.

6.1.1 Combined standard uncertainty

When the measurement results are obtained according to the values of several other quantities, the standard uncertainty of the measurement results is equal to the positive square root of the sum of variances of these other quantities. The influence of each item depends on the extent to which the measurement results change with these quantities.

6.1.2 Expanded uncertainty

The quantity that determines the range of measurement results. It is expected that most of the measured value distribution can be included in this interval.

6.1.3 Coverage factor

To obtain the expanded uncertainty, the numerical factor multiplied by the combined standard uncertainty.

Note 1: Generally, the coverage factor K is used in the range of 2 to 3.

Note 2: Unless otherwise required for special reasons, the inclusion factor used in gas analysis is K=2.

7 Traceability

Through an uninterrupted comparison chain with specified uncertainty, the measurement results or standard values can be linked with the specified reference standards, usually national standards or international standards.

Note 1: The unbroken comparison chain is called "traceability chain".

Note 2: The calibration mixture * * * can be traced back to the original calibration mixture.

8 Measurement standard

A physical measuring tool, measuring instrument, reference material or measuring system used as a reference standard for a defined, realized, saved or reproduced unit or one or more measurement values.

Note 1: The standard formed by the combination of a group of similar physical measuring tools or measuring instruments is called "combined standard".

Note 2: A group of standards for selecting values can be used separately or in combination to provide a numerical column of the same quantity, which is called "collective standard".

8.1 Reference material; RM

A material or chemical substance with one or more sufficiently uniform and fully determined characteristic values for calibrating instruments, evaluating measurement methods, or assigning values to materials.

8.2 Reference standard

A measurement standard with * * * high metrological characteristics adopted in a designated place or organization. All measurements made at this location are derived from it.

8.2.1 Primary standard

The values of the specified or generally accepted standards with * * * high metrological characteristics can be directly used, without comparison with other standards with the same value.

8.2.2 Secondary standard

The standard assigned by comparison with the primary standard of the same magnitude.