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Measurement uncertainity

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Guest user Created:   Oct 01, 2020 Last commented:   Oct 01, 2020

Measurement uncertainity

We are curtain wall, doors and windows performance testing laboratory. The representative sample of the door or windows (consists of aluminium profiles, glass, etc.) are installed in the lab as closed chamber. Resistance of the system to air, water and wind load are analysed by varying the pressure of the system. The range of pressure (negative and positive pressure) are as per the project specifications. We do the testing as per international standards (ASTM, CWCT, AAMA, BS) only. We have rotameters, pressure gauges, deflection gauges and water spray nozzle as the measuring instruments. All of them are externally calibrated. Final result are recorded as either passed or fail.
Is measurement of uncertainty applicable for our scope of work? what are factors to be considered if we requires to calculate the same? can you suggest some tools for the calculation?

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Tracey Evans Oct 01, 2020

You asked

Is measurement of uncertainty applicable for our scope of work? 

All testing laboratories must evaluate or, at least, estimate measurement uncertainty by identifying contributions to measurement uncertainty and considering all significant contributions including those arising from sampling and using appropriate methods of analysis. Where detailed measurement uncertainty evaluation is not possible due to the nature of the test method, the measurement uncertainty may be estimated based on principles of the techniques or practical experience of the performance of the method.

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what are factors to be considered if we requires to calculate the same? 

Measurement uncertainty is a statistical representation, representing the statistical certainty that the true result lies within the stated margin. It is understood as the margin of doubt regarding the results of any measurement.

To establish how large the margin of doubt is for a method, at a specified confidence level (e.g., 95% confidence), all the contributions (from your method steps and calcultions) must be included either a mathematical budget or by using long term quality control data of reproducibility and bias. It depends on the method and what you have available - standard uncertainties derived from various sources (such as calibrations) or long term “whole method” standard deviation

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can you suggest some tools for the calculation?"

For more information regarding the measurement uncertainty, see the ISO 17025 toolkit document template: Evaluation of Measurement Uncertainty Procedure at https://advisera.com/17025academy/documentation/evaluation-of-measurement-uncertainty-procedure/ This  covers the basic principles and steps to plan, measure and calculate the data required for an evaluation of measurement uncertainty. The two appendices related to the document, Measurement Uncertainty Checklist and Measurement Uncertainty Record support the process. I recommend you also look to your sector and suppliers for commonly used approaches.

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Oct 01, 2020

Oct 01, 2020

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