Instrument Abbreviation:
DPB, DPBC, DPT, DPTC
Instrument Measurements:
a) Trace Gas
Water Vapor
b) Cloud Physics/Aerosol
c) Radiation/Optical/Electrical
d) Additional Capabilities
Resource Person/Developer:
| Name: | Allen Schanot | Bruce Morley |
|---|---|---|
| Affiliation: | NCAR/ATD/RAF | NCAR/ATD/RAF |
| Phone: | (303)497-1063 | (303)497-1018 |
| Email: | schanot@ucar.edu | bruce@ucar.edu |
Principle of Measurement:
Ambient air passes through a small chamber housing a sensing mirror. A
Peltier thermoelectric cooler controls the mirror's temperature. As the
mirror temperature reaches the dew (or frost) point, condensate forms on its
surface causing its reflective characteristics to change. This change is
detected by photo-resistors in an optical sensing bridge and converted to
an electrical signal which drives the cooler thus stabilizing the mirror
temperature at a particular dew or frost layer thickness. The mirror
temperature, taken to be the dew/frost point temperature, is measured by
a platinum resistance thermometer. Frost points (measurements below 0C)
are converted back to an equivalent dew point during data processing.
In situ/Remote/Flux Measurement:
In situ
Field projects in which the instrument has been used:
most
Aircraft Platform:
all
Inlet Configuration/Location:
forward fuselage
Calibration/Cross Calibration:
NIST-traceable thermometers and electrical resistance standards
Operator Requirements:
Data Collection:
external
Post-flight Data Validation, Processing, Hours per Flight Hour etc.
RAF NIMBUS software processor
Post-project validation by RAF Project Manager
Phisical Characteristics:
Dimensions: Sensor: 2cm x 3cm x 4cm (HWD external)
Weight:
Power:
Other:
Response Time:
1s (humid conditions) to > 10s (depressions larger than 20C)
Detection Limits:
Accuracy:
+/- 0.5C ( > 0C )
+/- 1.0C ( < 0C )
Precision:
Limitations (such as altitude, airspeed, etc.)
Generally, the hygrometer has difficulty maintaining dewpoint depressions in
excess of 20 to 25C (RH < 10%).