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ASOS Barometer Calibration Verification.
The U. S. National Weather Service (NWS) maintains
and supports the Automated Surface Observation System (ASOS),
a complete weather monitoring and recording system.
Aircraft pilots receive digitally synthesized data on
weather conditions and Altimeter Setting information via radio
transmission from this equipment.
NWS purchases the model 760-16B as their
“Traveling Standard” for Calibration Verification of the
ASOS barometers in their Regions.
Digiquartz Barometers replaced Fortin Mercury Barometers
after demonstrating improved ease of use, high accuracy, and
long term stability. The
NWS calibrates their 760-16B digital barometers on a yearly
basis at a central facility for traceability and record
maintenance. The
unit has “proven to be a highly accurate (.01% of reading) and
reliable pressure instrument (little or no drift after 6
years)” per Reference 1.
The 760-16B stability specification is <0.003 in. Hg
per year.
AWOS Barometer Calibration Verification.
The U.S. Federal Aviation Agency (FAA) maintains and
supports the Automated Weather Observation System (AWOS),
a system similar to ASOS. For
this equipment, the FAA uses the 760-16B-3 as its “Traveling
Standard”, which is calibrated to a conformance of <0.002
in.Hg. This
calibration is performed via a NIST traceable, Class A, Primary
Standard on an annual basis.
Altimeter Setting Indicators (ASI).
Aircraft altimeters must be set to “true altitude”,
the local height above mean sea level.
This is accomplished through the conversion of ambient
barometric pressure to mean sea level pressure from data
provided through an Altimeter Setting Indicator (ASI) located at
the local airport.
Every ASI incorporates a highly accurate
barometer and converts local atmospheric conditions to Mean Sea
Level pressure values by knowing the exact elevation of the ASI
above sea level and using the U.S. Standard Atmosphere Table.
This data is available at Airports, FAA Regional Flight
Centers, Flight Service Stations and radio links to AWOS and
ASOS stations. Companies
contracted by the NWS and the FAA to provide Altimeter Setting
Indicators and the latest Digital Altimeter Setting Indicators,
incorporate Paroscientific Digiquartz Barometers because of
their high accuracy and long term stability.
Aircraft Air
Data Test Sets.
These test sets provide a means for calibrating and
testing Altimeters, Airspeed Indicators, Vertical Speed
Indicators and Encoding Altimeters, associated with the on-board
pitot-static pressure systems.
These Test Sets are typically used by FAA approved
maintenance & repair facilities, Airlines and Military
maintenance organizations and aircraft test facilities.
Calibration procedures require the Test Set barometers to be of
higher accuracy levels than those being calibrated.
The Paroscientific Model 215A/216B transducers and the
Model 6015/6016B Intelligent barometers are commonly used in
these applications because of their excellent performance
characteristics and established track record.
GPS Meteorology.
Global Positioning System (GPS) Meteorology is the
application of GPS data to the monitoring and analyses of
atmospheric conditions. Accurate,
frequent, and dense sampling of water vapor is needed for
operational weather forecasting as well as for weather and
climatic research.
The important ground-based measurements of
barometric pressure, temperature, and humidity necessary to
determine precipitable water vapor can be made with the
Paroscientific MET3 and MET3A Meteorological Measurement Systems, which
use Digiquartz Barometers.
This GPS Meteorological technique can recover
precipitable water vapor with an rms error of 1.0 to 1.5 mm and
represents a milestone improvement in environmental sensing
technology. More
accurate prediction of storm systems will improve surface,
coastal, and air travel safety.
Agriculture and farming will greatly benefit from these
models by improving crop yields and lead to a better
understanding of micro-climates.
GPS Meteorology and the construction,
operation, and performance of Digiquartz Barometers are
described in “Resonant Quartz
Barometers.”
Other Applications.
Paroscientific Barometers and the MET3 have been used
in a number of other applications where their Performance (<0.1
hPa) and Stability <0.1 hPa per year ) are important.
Examples include:
Drifting Buoys: Numerous
buoys instrumented with Paroscientific barometers have been
deployed by ships and aircraft to measure weather parameters
under difficult environmental conditions.
The National Hurricane Center in Florida air-deployed
three buoys in the paths of Hurricane Louis and Marilyn.
The buoys survived both storms and provided reliable,
accurate information even under 100 knot wind conditions.
Intercomparison Testing:
An
International Calibration Intercomparison initiated by the
Norwegian Meteorological Institute, DNMI, was performed on a Digiquartz Model
1016B Barometric Standard over a 5-year interval. It was compared with two primary pressure standards at
the Paroscientific Calibration Laboratory.
The Intercomparison Report shows that the five-year stability of the
device was -1.0 Pa per year (-0.01 hPa/yr).
The conformance (linearity) “as found” from 600 to
1100 hPa was +/-
1.0 Pa on a DH Instrument Standard dead weight tester and +/-
1.2 Pa (Bell & Howell Standard).
Both results are 2-sigma values including measurement
errors.
High Altitude Ballooning:
Barometric pressure measurements are made at
altitudes up to 130,000 feet where accuracy is essential for
these record setting attempts.
GPS Surveying and Mapping:
Elevation information is calculated through the
changes in barometric pressure associated with variations in
altitude and coordinated with the GPS-based latitude and
longitude locating system.
Missile & Satellite Laser Tracking:
Improved tracking accuracy is accomplished through
the computation of atmospheric delays similar to the GPS
Meteorology techniques used to compute Precipitable Water Vapor.
Laboratory
and Field Portable Barometric Standards:
Portability and ease of use, in addition to the high
accuracy, stability and resolution of the Digiquartz Barometers,
make these instruments ideal as Portable
Barometers.
Meteorological
Measurement Systems: The
Model 216B transducer is used to measure barometric pressure in
the MET4 and MET4A
systems.
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