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The use of humid air generator as a reference method for measuring humidity

Objective

The only primary method for measuring humidity that is currently recognised is the gravimetric method, which involves the determination of the water/air mass ratio. Unfortunately, the gravimetric method is difficult to use and requires long sampling times, particularly when dealing with low levels of humidity. Many laboratories therefore use the measurement of dew-point temperature in a humid air generator as a less costly and less complicated means to calibrate transfer standards or industrial hygrometers.

Several types of humid air generators are currently in use in Europe. The methods of humidification may involve single stage, multiple stage or recirculating processes, and may be carried out at either atmospheric or elevated pressures. This project aims to demonstrate which approach, if any, offers superior metrological properties. By applying comparable tests to each of the different types of humidity generator, unique information will be gained about the repeatability and the hysteresis of each method. If the metrological quality of the different types of humidity generators can be demonstrated, it will be possible to use dew-point generation as a reference method for humidity.
Two reference condensation hygrometers with chilled mirrors circulate since June 1995 in 8 national laboratories.

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Call for proposal

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Coordinator

CENTRE TECHNIQUE DES INDUSTRIES AERAULIQUES ET THERMIQUES
Address
Bd Du 11 Novembre 1918, 27-29
Villeurbanne
France
 

Participants (7)

Centre for Metrology and Accreditation
Finland
Address

00181 Helsinki
 
Eidgenossisches Amt für Meßwesen
Switzerland
Address
50,Lindenweg
3084 Wabern
 
Instituto Nacional de Técnica Aeroespacial 'Esteban Terradas'
Spain
Address
Car. Ajalvir Km. 4
28850 Madrid
 
NATIONAL RESEARCH COUNCIL OF ITALY
Italy
Address
Strada Delle Cacce 73
10135 Torino (Turin)
 
NMI B.V., INSTITUTE FOR METROLOGY AND TECHNOLOGY
Netherlands
Address
97,Schoenmakerstraat 97
2600 AR Delft
 
National Physical Laboratory (NPL)
United Kingdom
Address
Queen's Road
TW11 0LW Teddington
 
PHYSIKALISCH-TECHNISCHE BUNDESANSTALT
Germany
Address
Bundesallee 100
Braunschweig