Provision of traceability for absolute humidity

Project Description

The Standard Humidity Generators held at IMGC and at NPL are recognised as independent national primary standards of humidity dew-point traceable to the International Temperature Scale 1990 as realised in each country.

This Project recognises that the Primary Gravimetric Hygrometer held at NPL shall be the common standard of both Italy and the UK for absolute humidity. It provides for comparison of the Standard Humidity Generators in both countries with the Primary Gravimetric Hygrometer by appropriate means and their subsequent recognition as secondary standards for absolute humidity. It describes also the provision of calibration services and technology transfer related to humidity measurement.

The parties to this agreement are ready to consider its extension to include other EUROMET partners. UK (NPL) is ready to consider similar bi-lateral agreements with other individual EUROMET partners.

Final Report 2012-04-11

The project is now closed by agreement. Active cooperation between INRiM and NPL continues under a number of other mechnisms.
NPL has maintined an ongoing offer of traceability to its Primary Gravimetric Hygrometer for INRiM up to 2012. If any future activity on this is required, a new agreement may be sought.
INRiM has provided and developed national humidity standards for Italy based on humid air generators, and has disseminated traceability of humidity measurements to laboratories accredited for humidity calibration, and continues to do so.


Thermometry (T)
Coordinating Institute
NPL (United Kingdom)
Participating Partners
INRIM (Italy)