Measuring Accuracy
Messgenauigkeit | A service provided by |
|---|
|
| Polymer Service GmbH Merseburg |
| Tel.: +49 3461 30889-50 E-Mail: info@psm-merseburg.de Web: https://www.psm-merseburg.de |
| Our further education offers: https://www.psm-merseburg.de/weiterbildung |
| PSM on Wikipedia: https://de.wikipedia.org/wiki/Polymer Service Merseburg |
Measuring accuracy
Fundamental intruduction
A measurement is always subject to a certain degree of technical measurement uncertainty, which is expressed in the respective measurement result. The accuracy of the measured value (often also referred to as measurement accuracy) is documented in the approximation of the real measured value to the true or ideal measured variable.
In the case of measurement accuracy, expressed by the measurement uncertainty, a distinction is made between random measurement uncertainties and systematic measurement uncertainties. The random measurement uncertainties cannot be specifically corrected, whereas the systematic measurement uncertainties can be influenced by measurement technology or mathematics and can be corrected.
In DIN 1319 [1, 2], the ‘true’ value of the measurand parameter is described as an ideal value that is not normally known. The ‘true’ value of the measurand, on the other hand, is a ‘known’ value that is used as a reference for the measurements.
The measurement accuracy therefore indicates the extent to which the real measurement result deviates from the physically absolutely true result, regardless of whether it was determined incrementally or analogue. Absolute measured values are always considered and compared with a physically and metrologically almost perfect measuring device [3].
In metrology or measurement technology, precision and measurement accuracy are two essential criteria for assessing a measurement, whereby precision is described as a criterion for the quality of a measurement procedure and is therefore also considered to be the internal accuracy of a measurement.
The precision of a procedure is determined by repeating the measurement many times under reference conditions with the identical measuring device or measuring system by reducing the series of results obtained according to standardised algorithms of error and compensation calculation. A very precise measurement procedure produces almost identical series of results for the same measurement task. However, the precision does not allow any statements to be made about how far the individual measured values are from the real value. It only provides information about the stability of the measuring device, including the reading accuracy during the measurements.
Compared to precision, accuracy or measurement accuracy contains two fundamental pieces of information:
- The first is external accuracy, which is expressed in the dispersion of the mean values of the measured values if they are measured repeatedly and are subject to natural statistical deviations that cannot be influenced.
- But it is also an absolute accuracy, which reflects the degree of agreement between the displayed (real) and the true measured value.
High precision is therefore a necessary but not sufficient prerequisite for high accuracy, i.e. precision is a component of accuracy that is limited to the aspect of reproducibility of measurement results. Technical processes can run with high precision but still be imprecise; on the other hand, imprecise technology cannot produce accurate results.
See also
References
| [1] | DIN 1319-1 (1995-01): Fundamentals of Metrology – Part 1: Basic Terminology |
| [2] | DIN 1319-2 (2005-10): Fundamentals of Metrology – Part 2: Terminology Related to Measuring Equipment |
| [3] | Laible, M., Müller, R. K., Bill, B., Gehrke, K.: Mechanische Größen elektrisch gemessen – Grundlagen und Beispiele zur technischen Ausführung. Expert Verlag, Renningen (2009) 7. Auflage (ISBN 978-3-8169-2892-8) |