correcting dew point measurements for pressure imprtanceo of the correction processing...
TRANSCRIPT
![Page 1: Correcting Dew Point Measurements for Pressure Imprtanceo of the Correction Processing Considerations Recommendations Correcting Dew Point Measurements for Pressure Al Cooper RAF Algorithm](https://reader034.vdocuments.net/reader034/viewer/2022051600/5aae0bb37f8b9a6b308b8ca4/html5/thumbnails/1.jpg)
BackgroundImportance of the Correction
Processing ConsiderationsRecommendations
Correcting Dew Point Measurements for Pressure
Al Cooper
RAF Algorithm Review
10/12/2011
Al Cooper DP pressure
![Page 2: Correcting Dew Point Measurements for Pressure Imprtanceo of the Correction Processing Considerations Recommendations Correcting Dew Point Measurements for Pressure Al Cooper RAF Algorithm](https://reader034.vdocuments.net/reader034/viewer/2022051600/5aae0bb37f8b9a6b308b8ca4/html5/thumbnails/2.jpg)
BackgroundImportance of the Correction
Processing ConsiderationsRecommendations
WHY MEASURE HOUSING PRESSURE?
The Housing
Chilled mirror inside
Note small hole
Accelerated air�ow aroundnose and housing
Dew Point De�nition:
Temperature at whichambient vapor pressure isin equilibrium w/ water
Vapor pressure change:proportional to totalpressure
Al Cooper DP pressure
![Page 3: Correcting Dew Point Measurements for Pressure Imprtanceo of the Correction Processing Considerations Recommendations Correcting Dew Point Measurements for Pressure Al Cooper RAF Algorithm](https://reader034.vdocuments.net/reader034/viewer/2022051600/5aae0bb37f8b9a6b308b8ca4/html5/thumbnails/3.jpg)
BackgroundImportance of the Correction
Processing ConsiderationsRecommendations
WHY MEASURE HOUSING PRESSURE?
The Housing
Chilled mirror inside
Note small hole
Accelerated air�ow aroundnose and housing
Dew Point De�nition:
Temperature at whichambient vapor pressure isin equilibrium w/ water
Vapor pressure change:proportional to totalpressure
Al Cooper DP pressure
![Page 4: Correcting Dew Point Measurements for Pressure Imprtanceo of the Correction Processing Considerations Recommendations Correcting Dew Point Measurements for Pressure Al Cooper RAF Algorithm](https://reader034.vdocuments.net/reader034/viewer/2022051600/5aae0bb37f8b9a6b308b8ca4/html5/thumbnails/4.jpg)
BackgroundImportance of the Correction
Processing ConsiderationsRecommendations
WHY MEASURE HOUSING PRESSURE?
The Housing
Chilled mirror inside
Note small hole
Accelerated air�ow aroundnose and housing
Dew Point De�nition:
Temperature at whichambient vapor pressure isin equilibrium w/ water
Vapor pressure change:proportional to totalpressure
Al Cooper DP pressure
![Page 5: Correcting Dew Point Measurements for Pressure Imprtanceo of the Correction Processing Considerations Recommendations Correcting Dew Point Measurements for Pressure Al Cooper RAF Algorithm](https://reader034.vdocuments.net/reader034/viewer/2022051600/5aae0bb37f8b9a6b308b8ca4/html5/thumbnails/5.jpg)
BackgroundImportance of the Correction
Processing ConsiderationsRecommendations
SENSITIVITY TO PRESSURE
Vapor Pressure at Equilibrium
Change in vapor pressure of-50% or +100%:
near 0◦C, dew point changesby approx. 10◦Cnear -50◦C, dew pointchanges by approx. 6◦C
1◦C error in dewpoint for 8% changein vapor pressure @TDP = 0◦C;for 12% change @ TDP =−50◦C.±10% errors are signi�cant
Al Cooper DP pressure
![Page 6: Correcting Dew Point Measurements for Pressure Imprtanceo of the Correction Processing Considerations Recommendations Correcting Dew Point Measurements for Pressure Al Cooper RAF Algorithm](https://reader034.vdocuments.net/reader034/viewer/2022051600/5aae0bb37f8b9a6b308b8ca4/html5/thumbnails/6.jpg)
BackgroundImportance of the Correction
Processing ConsiderationsRecommendations
HOW LARGE IS THE PRESSURE DEVIATION?
Al Cooper DP pressure
![Page 7: Correcting Dew Point Measurements for Pressure Imprtanceo of the Correction Processing Considerations Recommendations Correcting Dew Point Measurements for Pressure Al Cooper RAF Algorithm](https://reader034.vdocuments.net/reader034/viewer/2022051600/5aae0bb37f8b9a6b308b8ca4/html5/thumbnails/7.jpg)
BackgroundImportance of the Correction
Processing ConsiderationsRecommendations
HOW LARGE IS THE PRESSURE DEVIATION?
PSXC (yellow) compared toPSDP{R,L} (cyan, green) -Note ca. 100 mb di�erenceat max altitude
→
Al Cooper DP pressure
![Page 8: Correcting Dew Point Measurements for Pressure Imprtanceo of the Correction Processing Considerations Recommendations Correcting Dew Point Measurements for Pressure Al Cooper RAF Algorithm](https://reader034.vdocuments.net/reader034/viewer/2022051600/5aae0bb37f8b9a6b308b8ca4/html5/thumbnails/8.jpg)
BackgroundImportance of the Correction
Processing ConsiderationsRecommendations
HOW LARGE IS THE PRESSURE DEVIATION?
Extreme deviations run upto 180 mb, with a pressurede�cit at high altitude.
→
Al Cooper DP pressure
![Page 9: Correcting Dew Point Measurements for Pressure Imprtanceo of the Correction Processing Considerations Recommendations Correcting Dew Point Measurements for Pressure Al Cooper RAF Algorithm](https://reader034.vdocuments.net/reader034/viewer/2022051600/5aae0bb37f8b9a6b308b8ca4/html5/thumbnails/9.jpg)
BackgroundImportance of the Correction
Processing ConsiderationsRecommendations
HOW LARGE IS THE PRESSURE DEVIATION?
Pressure correction will in-
crease the dew point. Com-parison with VCSEL (cyantrace) is already fairly good,may get worse?
→
Al Cooper DP pressure
![Page 10: Correcting Dew Point Measurements for Pressure Imprtanceo of the Correction Processing Considerations Recommendations Correcting Dew Point Measurements for Pressure Al Cooper RAF Algorithm](https://reader034.vdocuments.net/reader034/viewer/2022051600/5aae0bb37f8b9a6b308b8ca4/html5/thumbnails/10.jpg)
![Page 11: Correcting Dew Point Measurements for Pressure Imprtanceo of the Correction Processing Considerations Recommendations Correcting Dew Point Measurements for Pressure Al Cooper RAF Algorithm](https://reader034.vdocuments.net/reader034/viewer/2022051600/5aae0bb37f8b9a6b308b8ca4/html5/thumbnails/11.jpg)
Note valleys, L only
![Page 12: Correcting Dew Point Measurements for Pressure Imprtanceo of the Correction Processing Considerations Recommendations Correcting Dew Point Measurements for Pressure Al Cooper RAF Algorithm](https://reader034.vdocuments.net/reader034/viewer/2022051600/5aae0bb37f8b9a6b308b8ca4/html5/thumbnails/12.jpg)
BackgroundImportance of the Correction
Processing ConsiderationsRecommendations
ALGORITHM WHEN PSDPx IS AVAILABLE
Modi�ed DPXC
1 Obtain vapor pressure from measured DPx
2 Correct for �enhancement factor�
3 Scale vapor pressure by F={PSXC}/{PSDPx}4 Get DPXC via interpolation table, e to DPXC
Available since DC3-TEST, May 2011
Includes HIPPO-4, HIPPO-5, ICEBRIDGE
Al Cooper DP pressure
![Page 13: Correcting Dew Point Measurements for Pressure Imprtanceo of the Correction Processing Considerations Recommendations Correcting Dew Point Measurements for Pressure Al Cooper RAF Algorithm](https://reader034.vdocuments.net/reader034/viewer/2022051600/5aae0bb37f8b9a6b308b8ca4/html5/thumbnails/13.jpg)
BackgroundImportance of the Correction
Processing ConsiderationsRecommendations
ALGORITHM WHEN PSDPx IS AVAILABLE
Modi�ed DPXC
1 Obtain vapor pressure from measured DPx
2 Correct for �enhancement factor�
3 Scale vapor pressure by F={PSXC}/{PSDPx}4 Get DPXC via interpolation table, e to DPXC
Available since DC3-TEST, May 2011
Includes HIPPO-4, HIPPO-5, ICEBRIDGE
Al Cooper DP pressure
![Page 14: Correcting Dew Point Measurements for Pressure Imprtanceo of the Correction Processing Considerations Recommendations Correcting Dew Point Measurements for Pressure Al Cooper RAF Algorithm](https://reader034.vdocuments.net/reader034/viewer/2022051600/5aae0bb37f8b9a6b308b8ca4/html5/thumbnails/14.jpg)
BackgroundImportance of the Correction
Processing ConsiderationsRecommendations
OLD DATA
Errors
Errors range from slightlyhigh to 6C too low
Plateau at low DP ismoved from around -70Cto around -65C
Where VCSEL measuresabout -80C, DP now isbetween -60C and -65C
Are Errors Important?
Al Cooper DP pressure
![Page 15: Correcting Dew Point Measurements for Pressure Imprtanceo of the Correction Processing Considerations Recommendations Correcting Dew Point Measurements for Pressure Al Cooper RAF Algorithm](https://reader034.vdocuments.net/reader034/viewer/2022051600/5aae0bb37f8b9a6b308b8ca4/html5/thumbnails/15.jpg)
BackgroundImportance of the Correction
Processing ConsiderationsRecommendations
OLD DATA
Errors
Errors range from slightlyhigh to 6C too low
Plateau at low DP ismoved from around -70Cto around -65C
Where VCSEL measuresabout -80C, DP now isbetween -60C and -65C
Are Errors Important?
Al Cooper DP pressure
![Page 16: Correcting Dew Point Measurements for Pressure Imprtanceo of the Correction Processing Considerations Recommendations Correcting Dew Point Measurements for Pressure Al Cooper RAF Algorithm](https://reader034.vdocuments.net/reader034/viewer/2022051600/5aae0bb37f8b9a6b308b8ca4/html5/thumbnails/16.jpg)
BackgroundImportance of the Correction
Processing ConsiderationsRecommendations
OLD DATA
Errors
Errors range from slightlyhigh to 6C too low
Plateau at low DP ismoved from around -70Cto around -65C
Where VCSEL measuresabout -80C, DP now isbetween -60C and -65C
Are Errors Important?
Al Cooper DP pressure
![Page 17: Correcting Dew Point Measurements for Pressure Imprtanceo of the Correction Processing Considerations Recommendations Correcting Dew Point Measurements for Pressure Al Cooper RAF Algorithm](https://reader034.vdocuments.net/reader034/viewer/2022051600/5aae0bb37f8b9a6b308b8ca4/html5/thumbnails/17.jpg)
BackgroundImportance of the Correction
Processing ConsiderationsRecommendations
POSSIBLE CORRECTION PROCEDURE
Find which aspects of �ightconditions determine the pressurede�cit
From exploring these possibilities,found PSXC, XMACH2, QCRCseem to be best
Fit determined for HIPPO-4 RF01.(Coe�cients in memo)
Possible dependence on PSXC,Mach No, TAS, QCRC, ATTACK,SSLIP.
Best �t, for PSDPL:
PDP = Paa(a0 +a1∆p+a2M2)
Test: apply to DC3-TEST (RF03),di�erent project and di�erent �ightpro�le
Al Cooper DP pressure
![Page 18: Correcting Dew Point Measurements for Pressure Imprtanceo of the Correction Processing Considerations Recommendations Correcting Dew Point Measurements for Pressure Al Cooper RAF Algorithm](https://reader034.vdocuments.net/reader034/viewer/2022051600/5aae0bb37f8b9a6b308b8ca4/html5/thumbnails/18.jpg)
BackgroundImportance of the Correction
Processing ConsiderationsRecommendations
POSSIBLE CORRECTION PROCEDURE
Find which aspects of �ightconditions determine the pressurede�cit
From exploring these possibilities,found PSXC, XMACH2, QCRCseem to be best
Fit determined for HIPPO-4 RF01.(Coe�cients in memo)
Possible dependence on PSXC,Mach No, TAS, QCRC, ATTACK,SSLIP.
Best �t, for PSDPL:
PDP = Paa(a0 +a1∆p+a2M2)
Test: apply to DC3-TEST (RF03),di�erent project and di�erent �ightpro�le
Al Cooper DP pressure
![Page 19: Correcting Dew Point Measurements for Pressure Imprtanceo of the Correction Processing Considerations Recommendations Correcting Dew Point Measurements for Pressure Al Cooper RAF Algorithm](https://reader034.vdocuments.net/reader034/viewer/2022051600/5aae0bb37f8b9a6b308b8ca4/html5/thumbnails/19.jpg)
BackgroundImportance of the Correction
Processing ConsiderationsRecommendations
POSSIBLE CORRECTION PROCEDURE
Find which aspects of �ightconditions determine the pressurede�cit
From exploring these possibilities,found PSXC, XMACH2, QCRCseem to be best
Fit determined for HIPPO-4 RF01.(Coe�cients in memo)
Possible dependence on PSXC,Mach No, TAS, QCRC, ATTACK,SSLIP.
Best �t, for PSDPL:
PDP = Paa(a0 +a1∆p+a2M2)
Test: apply to DC3-TEST (RF03),di�erent project and di�erent �ightpro�le
Al Cooper DP pressure
![Page 20: Correcting Dew Point Measurements for Pressure Imprtanceo of the Correction Processing Considerations Recommendations Correcting Dew Point Measurements for Pressure Al Cooper RAF Algorithm](https://reader034.vdocuments.net/reader034/viewer/2022051600/5aae0bb37f8b9a6b308b8ca4/html5/thumbnails/20.jpg)
BackgroundImportance of the Correction
Processing ConsiderationsRecommendations
FIT RESULTS
�
�Black Line:
Measured PSDPL�
�Thin red line:
Results of �t
Fit RMS: 7.9 mb
Al Cooper DP pressure
![Page 21: Correcting Dew Point Measurements for Pressure Imprtanceo of the Correction Processing Considerations Recommendations Correcting Dew Point Measurements for Pressure Al Cooper RAF Algorithm](https://reader034.vdocuments.net/reader034/viewer/2022051600/5aae0bb37f8b9a6b308b8ca4/html5/thumbnails/21.jpg)
BackgroundImportance of the Correction
Processing ConsiderationsRecommendations
APPLICATION TO A DIFFERENT FLIGHT
Al Cooper DP pressure
![Page 22: Correcting Dew Point Measurements for Pressure Imprtanceo of the Correction Processing Considerations Recommendations Correcting Dew Point Measurements for Pressure Al Cooper RAF Algorithm](https://reader034.vdocuments.net/reader034/viewer/2022051600/5aae0bb37f8b9a6b308b8ca4/html5/thumbnails/22.jpg)
BackgroundImportance of the Correction
Processing ConsiderationsRecommendations
CONCLUSIONS
Recommendations:
1 Add processing to include the e�ect of the measured pressure,as follows:
1 Calculate the pressure ratio PSXC/PSDPx =Rx2 Multiply the vapor pressure by Rx after converting from
measured dew point to vapor pressure.3 Use this modi�ed vapor pressure as the output variable EDPC.4 Use the interpolation table to �nd the dew point temperature.
2 For old GV data, consider reprocessing with the pressuredetermined from (1) to correct for rather large errors in thedew point measurements, which can be 5-10◦C.
3 Change the �long_name� of DPLC and DPRC to distinguishthem from DPLS/DPRS.
Al Cooper DP pressure
![Page 23: Correcting Dew Point Measurements for Pressure Imprtanceo of the Correction Processing Considerations Recommendations Correcting Dew Point Measurements for Pressure Al Cooper RAF Algorithm](https://reader034.vdocuments.net/reader034/viewer/2022051600/5aae0bb37f8b9a6b308b8ca4/html5/thumbnails/23.jpg)
BackgroundImportance of the Correction
Processing ConsiderationsRecommendations
CONCLUSIONS
Recommendations:
1 Add processing to include the e�ect of the measured pressure,as follows:
1 Calculate the pressure ratio PSXC/PSDPx =Rx2 Multiply the vapor pressure by Rx after converting from
measured dew point to vapor pressure.3 Use this modi�ed vapor pressure as the output variable EDPC.4 Use the interpolation table to �nd the dew point temperature.
2 For old GV data, consider reprocessing with the pressuredetermined from (1) to correct for rather large errors in thedew point measurements, which can be 5-10◦C.
3 Change the �long_name� of DPLC and DPRC to distinguishthem from DPLS/DPRS.
Al Cooper DP pressure
![Page 24: Correcting Dew Point Measurements for Pressure Imprtanceo of the Correction Processing Considerations Recommendations Correcting Dew Point Measurements for Pressure Al Cooper RAF Algorithm](https://reader034.vdocuments.net/reader034/viewer/2022051600/5aae0bb37f8b9a6b308b8ca4/html5/thumbnails/24.jpg)
BackgroundImportance of the Correction
Processing ConsiderationsRecommendations
CONCLUSIONS
Recommendations:
1 Add processing to include the e�ect of the measured pressure,as follows:
1 Calculate the pressure ratio PSXC/PSDPx =Rx2 Multiply the vapor pressure by Rx after converting from
measured dew point to vapor pressure.3 Use this modi�ed vapor pressure as the output variable EDPC.4 Use the interpolation table to �nd the dew point temperature.
2 For old GV data, consider reprocessing with the pressuredetermined from (1) to correct for rather large errors in thedew point measurements, which can be 5-10◦C.
3 Change the �long_name� of DPLC and DPRC to distinguishthem from DPLS/DPRS.
Al Cooper DP pressure