Um estudo aplicado da carta de controle e incerteza de medição

Abstract

The current market requires companies to improve the quality of services provided to the customer. Some general requirements for the competence of testing laboratories include the assessment of measurement uncertainty as well as ensuring the conformity of measuring equipment. Therefore, mean and amplitude control charts were used to monitor the analytical balance, pH meter, and sulfate and nitrate tests. Furthermore, the main sources that contribute to measurement uncertainty were investigated. The procedures recommended in the Eurachem, GUM, and ISOBudget guides were adopted. According to the control charts, the analytical balance operates correctly up to the 50-gram range, as there is evidence of loss of performance from 100 grams onward. The pH meter is out of control for the three pH ranges studied, requiring corrective action from the laboratory. The sulfate test is inadequate because the values obtained from the internal reference material do not follow a normal distribution, proven by the Shapiro-Wilk test whose p-value < 0.05. The nitrate test proved to be appropriate since the sample points obtained were within the control limits. Repeatability and reproducibility were the main sources contributing to measurement uncertainty in all equipment and tests studied.