BS ISO 9644:2018 pdf free

BS ISO 9644:2018 pdf free.Agricultural irrigation equipment一Pressure losses in irrigation valves
Measurements are inevitably marred with uncertainty even though the measurement procedure and instrument, as well as the analysis methods, strictly meet the existing rules and, more specifically, the procedures in this document.
Measurement uncertainty partly depends on residual uncertainty in the instruments or the measurement method. Once all known errors are cancelled by calibration and when dimension measurements are strictly recorded and the facility suitably prepared, there remains an uncertainty which is never cancelled and cannot be reduced by measurement repetition, if the same instrument and the same measuring method are implemented. The evaluation of this uncertainty component based on the knowledge of the instrument used and the measurement methods is referred to as systematic uncertainty.
Another source of error due either to the measurement system properties or the measured quantity variations, or to both, directly appears in the form of measurement spread. The evaluation of this measurement uncertainty component is referred to as random uncertainty. Its evaluation requires the measurement and analysis (by statistic methods in cases) of the fluctuations and the stability of the measured physical quantities.
To reduce systematic uncertainty, the operators resort to more precise instruments or apply several measurement methods.
With the same instrument and measurement method, the uncertainty caused by random uncertainty can be reduced by increasing the number of measurements for the same physical quantity, in the same conditions.
When systematic and random uncertainties are determined, the total measurement uncertainty is calculated as the square root of the sum of the squares of the systematic and random uncertainty.
However, in this document, if the requirements pertaining to systematic uncertainty (in 4.1) and if all requirements imposed on the test procedure (as indicated in this document) are applied, it can be assumed that total uncertainty does not exceed the values stated in
The examples below are based on the assumption that the physical quantities to be measured are not damped before their acquisition by the measurement systems.
If the measurement device does not include an electronic damper system, the signal values from the measurement device are subject to fluctuations during the time required for acquisition.BS ISO 9644 pdf download.