http:// economie.fgov.be Miruna DOBRE – SMD (Belgium) Stephanie BELL – NPL (United Kingdom) Dolores del CAMPO – CEM (Spain) Martti HEINONEN - MIKES (Finland) Domen HUDOKLIN – LMK (Slovenia) Giuseppina LOPARDO , Andrea MERLONE – INRIM (Italy) METROLOGICAL TRACEABILITY FOR METEOROLOGICAL SENSORS ILLUSTRATED THROUGH EXAMPLES
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Http://economie.fgov.be Miruna DOBRE – SMD (Belgium) Stephanie BELL – NPL (United Kingdom) Dolores del CAMPO – CEM (Spain) Martti HEINONEN - MIKES (Finland)
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http://economie.fgov.be
Miruna DOBRE – SMD (Belgium)Stephanie BELL – NPL (United Kingdom)
Dolores del CAMPO – CEM (Spain)Martti HEINONEN - MIKES (Finland) Domen HUDOKLIN – LMK (Slovenia)
Giuseppina LOPARDO , Andrea MERLONE – INRIM (Italy)
METROLOGICAL TRACEABILITY
FOR METEOROLOGICAL SENSORS
ILLUSTRATED THROUGH
EXAMPLES
Why do I need traceability?
International Vocabulary for Metrology (VIM) definition: “property of a measurement result whereby the result can be related to a referencereference through a documented unbroken chain of calibrationschain of calibrations, each contributing to the measurement uncertaintymeasurement uncertainty”.
•Vapour pressure (partial pressure) of water (in units of pressure)
•Dew-point temperature [and frost point] (in units of temperature)
•Composition (dimensionless)
•Relative humidity (dimensionless) but symbol %rh used (also %hr,
%ur, %rF, etc) - not very standardised!
•And other less-used parameters
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Humidity primary standards
• By measurements: gravimetric hygrometer
• By realizations: a system that can produce a gas stream of known humidity
By saturation at defined pressure(s) and temperature(s)
By gas blending, …
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Absolute humidity generator operation:
1.Saturate the gas with water at a known temperature and pressure. The mole fraction x of water vapor in the gas is
2.For 2-p expand till atmosphere, for divided flow mix with known amounts of dry gas (traceable flowmeters)
ssss PPTfTex ,
Humidity = mass mass of water vapor in a unit volumevolume of moist air at a given temperaturetemperature and pressurepressure.
water vapor pressure enhancement factor
uncertainty due to formulae calculations
Humidity primary standards
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Humidity primary standards
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Traceability scheme for humidity measurements
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Traceability scheme for humidity measurements
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Primary standards in pressure measurement
Hgp
m
p
A
Agmp
Temperature reference
Important influence
Mass reference
Length reference
Laser interferometric manometer
Piston gauge
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Other effects affecting measurement result:
•dilatation of piston and cylinder due to temperature and pressure;•surface tension effects around piston;•air buoyancy over masses;• liquid column head,•….
Primary standards in pressure measurement
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A measurement has metrological traceability if:
1. An unbroken and documented chain of calibrations links the
instrument to an internationally agreed reference;
2. Each chain link has documented uncertainty estimations;
3. The final user has procedures to ensure that the instrument
maintains its calibration with associated uncertainties over
time;
4. The influence factors affecting the measurement are
quantified and a total measurement uncertainty is calculated,