Calibration curve computing (CCC) software v2.0: A new release of the INRIM regression tool

The main features of the Calibration Curve Computing (CCC) Software, a tool for regression analysis developed at the INRIM, the Italian National Metrology Institute, are described in this paper. The first release of the software tool, version 1.3, has been available on the INRIM website for free download since 2015. It was developed under a Matlab environment and distributed as an executable file. The software tool featured a friendly graphical user interface, to encourage even non-Matlab users to use it. The software is able to perform regression fitting according to ordinary,weighted and weighted total least square models and it can be applied to datasets that can be characterized by uncertainties and covariances in both the dependent and the independent variable. The curves that can be fitted to the data are fractional polynomials with positive and negative exponents up to the fifth order. Recently, version 2.0 of the CCC Software has been developed and tested and will be uploaded early in 2020. The main improvements of this new version, concerning the graphical aspects and the calculation functionalities, are here described in detail, with a major focus on the enhancements obtained in the estimated accuracy of the weighted total least square regression. Validation results and the application to a real case study are also shown. The present paper is a significant expansion of a relevant abstract presented at the 'Mathematical and Statistical Methods for Metrology' Workshop, Torino, Italy, 30-31 May 2019 (Lecuna et al 2019 Mathematical and Statistical Methods for Metrology)

The use of dynamic dilution by Mass Flow Controllers in the environmental monitoring of CO2: calibration issues and strategies

Gaseous pollutants determination in atmosphere is usually carried out by comparison methods with dedicated analysers, which need to be calibrated with proper certified reference gas mixtures. D ynamic dilution allows the generation of gas mixtures which can be employed either to calibrate the analysers or to validate gas mixtures contained in high pressure cylinders. The dynamic dilution is often achieved by using Mass Flow Controllers (MFCs) due to their ease of use and good level of reliability. The MFC sensors are based on heat exchange equations, therefore the response of these instruments is sensitive to the nature of the flowing gas. The different response can be taken into account through a so-called Gas Correction Factor (GCF), which can be computed when the gas properties are known. Neglecting the use of proper GCFs may result in a bias in the assignment of the molar fraction of dynamic mixtures. The present paper deals with the calculation carried out at INRIM of the GCF in the generation of dynamic mixtures of carbon dioxide in synthetic air at ambient level. The results obtained without using the GCFs are compared with those obtained by application of the correction, showing the presence of a systematic non-negligible bias

Calibration Curve Computing (CCC) software v2.0: A new version of INRIM’s software for regression analysis

Presentation of the features introduced in the version 2.0 of INRIM's public software for the evaluation of the uncertainty in linear regressions