PD ISO/TS 28038:2018 Determination and use of polynomial calibration functions

PD ISO/TS 28038:2018

Determination and use of polynomial calibration functions

Status : Current   Published : December 2018



What is this standard about?

1.1 This document is concerned with polynomial calibration functions that describe the relationship between a stimulus variable and a response variable. These functions contain parameters estimated from calibration data consisting of a set of pairs of stimulus value and response value. Various cases are considered relating to the nature of any uncertainties associated with the data.

1.2 Estimates of the polynomial function parameters are determined using least‐squares methods, taking account of the specified uncertainty information. It is assumed that the calibration data are fit for purpose and thus the treatment of outliers is not considered. It is also assumed that the calibration data errors are regarded as drawn from normal distributions. An emphasis of this document is on choosing the least‐squares method appropriate for the nature of the data uncertainties in any particular case. Since these methods are well documented in the technical literature and software that implements them is freely available, they are not described in this document.

1.3 Commonly occurring types of covariance matrix associated with the calibration data are considered covering (a) response data uncertainties, (b) response data uncertainties and covariances, (c) stimulus and response data uncertainties, and (d) stimulus data uncertainties and covariances, and response data uncertainties and covariances. The case where the data uncertainties are unknown is also treated.

1.4 Methods for selecting the degree of the polynomial calibration function according to prescribed criteria are given. The covariance matrix associated with the estimates of the parameters in the selected polynomial function is available as a by‐product of the least‐squares methods used.

1.5 For the chosen polynomial function this document describes the use of the parameter estimates and their associated covariance matrix for inverse and direct evaluation. It also describes how the provisions of ISO/IEC Guide 98‐3:2008 (GUM) can be used to provide the associated standard uncertainties.

1.6 Consideration is given to accounting for certain constraints (such as the polynomial passing through the origin) that may need to be imposed and also to the use of transformations of the variables that may render the behaviour of the calibration function more polynomial‐like. Interchanging the roles of the variables is also considered.

1.7 Examples from several areas of measurement science illustrate the use of this document

Standard NumberPD ISO/TS 28038:2018
TitleDetermination and use of polynomial calibration functions
Publication Date21 December 2018
Normative References(Required to achieve compliance to this standard)ISO/IEC Guide 99:2007, ISO/IEC Guide 98-3:2008
Informative References(Provided for Information)ISO 6143:2001, ISO/TS 28037:2010, ISO 11095:1996, ISO 7066-2:1988, ISO 11843-5, ISO 11843-2, ISO/IEC Guide 98-3:2008
International RelationshipsISO/TS 28038:2018
DescriptorsComparative tests, Measurement, Probability theory, Bias, Statistical methods of analysis, Statistical testing, Reproducibility, Measurement characteristics, Estimation
Title in FrenchDétermination et utilisation des fonctions d'étalonnage polynômial
ISBN978 0 580 98098 5
File Size3.07 MB

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