Читать книгу Introduction to Desalination - Louis Theodore - Страница 57

All measurements and calculations are subject to two broad classes of errors: determinate and indeterminate. Any error that is discovered and allowed for in magnitude and sign in the form of a correction allowing for its effect is a “determinate error.” All errors that either cannot be or are not properly allowed for in magnitude and in sign are known as “indeterminate errors.” A particularly important class of indeterminate errors is that of accidental errors. Qualitatively discuss these two error types.

Solution. Determinate errors are systematic errors that can be discovered and corrected. Determinate errors include instrument errors, i.e. calibration errors, power fluctuations, method errors, i.e. sampling problems, inconsistent recovery, and personal errors, i.e. errors that occur when measurements require judgment, color interpretation, etc. Determinate errors can be corrected via proper instrument calibration, method development, or training. To illustrate the nature of indeterminate errors, consider the very simple and direct measurement of temperature. Suppose that several independent readings are made and that the temperature varies by 0.1°F. When the results of the different readings are compared, it may be found that even though they have been performed very carefully, they may differ from each other by several tenths of a degree. Experience has shown that such deviations are inevitable in all measurements and that they result from small unavoidable random errors of observation due to the sensitivity of measuring instruments and the keenness of the sense of perception. Such errors are due to the combined effect of a large number of undetermined causes and they can be defined as accidental or indeterminate errors (Prochaska and Theodore 2018; Theodore and Behan 2018).