September 7 th 2001, 1 Radiation thermometry Uncertainties on measurements on Tungsten strip-lamps

September 7 th 2001, 2 Subject of interest Base Strip

September 7 th 2001, 3 Uncertainty budget Phrase subject into context Sources (alphabetic order) Base temperature Current Drift Emissivity Positioning Quality of polynomial fit Scale realization Transmission of window 1. Derive its magnitude 2. Find order of importance

September 7 th 2001, 4 Magnitude - Base temperature Base temperature has influence on temperature of strip and needs to be corrected for when deviating from T ref base (Uncertainty 10%) Minimize correction, water-cooled base: T base =(20±0.1)°C over entire range of operation Magnitude 5 mK at 962°C Type B evaluation T strip (ºC)  T strip /  T base (mK/ºC)

September 7 th 2001, 5 Magnitude - Current Instruments involved Current supply (stability  I/I  5x10 -5 ) Zero-flux meter (equivalent  I/I  1x10 -5 ) Voltmeter (equivalent  I/I  1x10 -4, Keithley 181 ) Magnitude A  54 mK at 962°C Type A evaluation

September 7 th 2001, 6 Magnitude - Drift Stability test: operate lamp for °C Requirement:  T/  t < 3 mK / hr over 100 hrs History provides information on correction Drift behaviour can be used to give an estimate of drift during calibration Traceability route and context of measurement determines whether this source of uncertainty is relevant Magnitude negligible Type B evaluation

September 7 th 2001, 7 Magnitude - Emissivity The emissivity  ( ) of Tungsten is involved when converting T rad from pyrometer to 650 nm. Values  ( ) of de Vos are used Only uncertainty in relative change of  ( ) is of importance; estimate 0.5% Magnitude 3 mK at 962°C Type B evaluation

September 7 th 2001, 8 Magnitude - Positioning-1 Displacement 2x horizontal, 1x vertical Rotation around vertical/horizontal From profile measurements Determine sensitivity around zero (%/mm, %/°) Estimate uncertainty in determination of position Magnitude 53 mK at 962°C Type A evaluation Vert. Hor. Rot.

September 7 th 2001, 9 Magnitude - Positioning-2 ActionSensitivity Estimate in zero Uncertainty Left-right 0.1 %/mm0.1 mm0.01% Up-down 0.1 %/mm0.1 mm0.01% Back-forward0.01 %/mm0.5 mm0.005% Rotate vertical 0.05 %/°1°0.05% Rotate horizontal 0.02 %/°1°0.02% Total 0.06%  53 mK

September 7 th 2001, 10 Magnitude - Quality of fit Polynomial fit: t 90 =  a i ln(S), with a=0..5 Least squares residuals result in 26 mK Magnitude 26 mK at 962°C Type A evaluation

September 7 th 2001, 11 Magnitude - Scale realization Standard 650 nm Magnitude 51 mK at 962°C Type B evaluation SourceType Uncertainty (mK) 962°C1300°C1700°C RealizationB81422 EmissivityB111 ResponseA+B8914 LinearityB123 SSEB234 WavelengthB01745 DriftB Total

September 7 th 2001, 12 Magnitude - Trans. window The transmission  ( ) of the window is involved when converting T rad from pyrometer to 650 nm. Values  ( ) of Pyrex material are used Only uncertainty in relative change of  ( ) is of importance; estimate 0.1% Magnitude 1 mK at 962°C Type B evaluation

September 7 th 2001, 13 Order of importance Source Type of evaluation Important ?Magnitude CurrentAYES54 mK PositioningAYES53 mK Scale realizationBYES51 mK Quality fitAYES/NO26 mK BaseBNO5 mK EmissivityBNO3 mK Transmission windowBNO1 mK DriftB--

September 7 th 2001, 14 EA-4/02 Expression of the uncertainty of Measurement in Calibration QuantityEstimateStandard uncertainty Sensitivity coefficient Contribution to the standard uncertainty Current 4 A0.44 mA8.2 mA/K54 mK Positioning 0.06%1.13 %/K53 mK Scale realization 962°C51 mK1 Quality fit 26 mK Combined95 mK K-factor2 Expanded190 mK

September 7 th 2001, 15 Conclusion Uncertainty in measurements associated with Tungsten strip lamps is at NMi-VSL dominated by 4 contributions (1. Current) 2. Positioning 3. Scale realization 4. Quality of the fit For NMi-VSL the overall uncertainty is evaluated to values for k=2 and 95% confidence interval: T 90 (X) 962°C1300 °C1700 °C U(T 90 (X)) 190 mK280 mK420 mK