Radiation thermometry

1
Radiation thermometry

• Uncertainties on measurements
• on
• Tungsten strip-lamps

2
Subject of interest
Strip
Base
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

4
Magnitude - Base temperature

• Base temperature has influence on temperature
• of strip and needs to be corrected for when
• deviating from Trefbase (Uncertainty 10)
• Minimize correction, water-cooled base
  Tbase(200.1)C over entire range of operation
• Magnitude 5 mK at 962C
• Type B evaluation

Tstrip (ºC) 700 800 900 1000 1100
? Tstrip /? Tbase (mK/ºC) 470 250 110 47 17
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 0.44 mA _at_ 4 A ? 54 mK at 962C
• Type A evaluation

6
Magnitude - Drift

• Stability test operate lamp for100 hrs _at_ 1700C
  
• Requirement ?T/?t lt 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

7
Magnitude - Emissivity

• The emissivity ?(?) of Tungsten is involved when
• converting Trad 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 962C
• Type B evaluation

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 962C
• Type A evaluation

9
Magnitude - Positioning-2
Action Sensitivity Estimate in zero Uncertainty
Left-right 0.1 /mm 0.1 mm 0.01
Up-down 0.1 /mm 0.1 mm 0.01
Back-forward 0.01 /mm 0.5 mm 0.005
Rotate vertical 0.05 / 1 0.05
Rotate horizontal 0.02 / 1 0.02
Total 0.06 ? 53 mK
10
Magnitude - Quality of fit

• Polynomial fit t90? ai ln(S), with a0..5
• Least squares residuals result in 26 mK
• Magnitude 26 mK at 962C
• Type A evaluation

11
Magnitude - Scale realization

• Standard pyrometer
• _at_ 650 nm
• Magnitude 51 mK at 962C
• Type B evaluation

Source Type Uncertainty (mK) Uncertainty (mK) Uncertainty (mK)
Source Type 962C 1300C 1700C
Realization B 8 14 22
Emissivity B 1 1 1
Response AB 8 9 14
Linearity B 1 2 3
SSE B 2 3 4
Wavelength B 0 17 45
Drift B 50 82 128
Total 51 86 138
12
Magnitude - Trans. window

• The transmission ?(?) of the window is involved
• when converting Trad 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 962C
• Type B evaluation

13
Order of importance
Source Type of evaluation Important ? Magnitude
Current A YES 54 mK
Positioning A YES 53 mK
Scale realization B YES 51 mK
Quality fit A YES/NO 26 mK
Base B NO 5 mK
Emissivity B NO 3 mK
Transmission window B NO 1 mK
Drift B - -
14
EA-4/02 Expression of the uncertainty of
Measurement in Calibration
Quantity Estimate Standard uncertainty Sensitivity coefficient Contribution to the standard uncertainty
Current 4 A 0.44 mA 8.2 mA/K 54 mK
Positioning 0.06 1.13 /K 53 mK
Scale realization 962C 51 mK 1 51 mK
Quality fit 26 mK
Combined 95 mK
K-factor 2
Expanded 190 mK
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 k2 and 95 confidence interval

T90(X) 962C 1300 C 1700 C
U(T90(X)) 190 mK 280 mK 420 mK