to Measure is to Know but how to measure?

Transcription

1 to Measure is to Know but how to measure? Gert Rietveld Nederlands Meetinstituut Delft VKRT meeting 8 Feb

2 Nederlands Meetinstituut Legal inspection Testing and certification Scientific metrology (national standards) VKRT meeting 8 Feb

3 Overview Measurement in daily life and in your profession How to make a good measurement? What is a measurement? Uncertainty Effects affecting measurements Units & the role of NMi Pass/fail testing ISO requirements Summary VKRT meeting 8 Feb

4 You wake up VKRT meeting 8 Feb

5 Make a cup of tea VKRT meeting 8 Feb

6 On the road VKRT meeting 8 Feb

7 Fill up with petrol VKRT meeting 8 Feb

8 Complement breakfast VKRT meeting 8 Feb

9 Oops! VKRT meeting 8 Feb

10 Do your shopping VKRT meeting 8 Feb

11 Make a small bet VKRT meeting 8 Feb

12 Take a taxi home VKRT meeting 8 Feb

13 Measuring in your job Production and testing of materials: Weight Temperature Force Time Hardness Length Volume Strength Particle size VKRT meeting 8 Feb

14 Measurement What do you want to know? How are you doing the measurement? How good is the measurement? The art of measurement De Geograaf Jan Vermeer VKRT meeting 8 Feb

15 Metrology and standaards Metrology: the science of measurement Why measurement standards and calibrations? We do know the length of a meter You can not thrust measurement equipment without verification! VKRT meeting 8 Feb

16 to Measure is to Know What is a measurement? Comparison to a reference Result: ±? Value = number x unit VKRT meeting 8 Feb

17 Uncertainty Uncertainty the qualification of the result of the measurement In which band can I expect the true value, related to the indication of the instrument Simply said: Uncertainty is lack of information VKRT meeting 8 Feb

18 Uncertainty Precise Accurate VKRT meeting 8 Feb

19 Uncertainty sources Noise, repeatability (imprecision) Systematic effects: Environment (air, oil, water, etc) Temperature of test setup and of environment Sample dimensions Time, drifts Resolution Offsets, biases Human factor (operator) Errors in analysis (Arrhenius plot) Sample preparation Reference equipment (calibration!) Etc. the less you know, the better you measure VKRT meeting 8 Feb

20 Sample preparation Batch reproduction how stable is production? Sampling within batch how homogeneous is production? VKRT meeting 8 Feb

21 to measure is to know What is a measurement? Comparison with a reference Result: Value = number x unit Task of NMi - SI units! VKRT meeting 8 Feb

22 History of the meter 4000 BC Egypt Cubit Forearm Pharaoh 1130 England Yard Nose to thumb King 1790 France Meter Circumference earth 1799 France Meter Pt rod 1960 CGPM Meter Wavelength Kr line 1983 CGPM Meter Speed of light VKRT meeting 8 Feb

23 The ultimate kg Grand K BIPM: scientific centre for metrology, depository of the Grand K mass reference VKRT meeting 8 Feb

24 Compare measurements NL DE? Industry requires traceability! Unbroken chain of measurements to (inter)national measurement standards VKRT meeting 8 Feb

25 Compare measurements (2) NL UK DE Via traceability Comparable measurements! VKRT meeting 8 Feb

26 1 kg Key comparison VKRT meeting 8 Feb

27 Pass / fail margins Nominal value PASS UNDEFINED FAIL : measurement value with 95% uncertainty interval (k=2) VKRT meeting 8 Feb

28 Doping - guilty or not? Player ng/ml Player ng/ml 2 ng/ml zero VKRT meeting 8 Feb

29 ISO requirements test & cal labs ISO requirements for test and calibration laboratories: Management system equivalent to ISO 9001 Technical competence Personnel Test procedures Measurement uncertainty Test equipment Cross-checks Quality control interlaboratory tests VKRT meeting 8 Feb

30 ISO standards for testing Sample characteristics Preparation of samples Describe test method Critical attention points Uncertainty contributions Minimum number of contributions: repeatability, reproducibility + systematic effects Methods for determining uncertainty Typical uncertainty budget VKRT meeting 8 Feb

31 To Measure is to Know A measurement value without uncertainty is meaningless Precise accurate Behing each measurement there is a standard (preferably a quantum standard) Only traceable measurement values can be compared with each other Knowing = measuring = our profession! VKRT meeting 8 Feb

32 Nederlands Meetinstituut The art of measurement De Geograaf Jan Vermeer VKRT meeting 8 Feb