Key comparison(s) in humidity (dew-point temperature)

Project Description

A key comparison is being planned between European national measurement institutes in the field of humidity. The aim of comparison is to demonstrate equivalence between humidity (dew point) realisations, in support of the CIPM Mutual Recognition Arrangement. The method of comparison will be calibration of dew-point hygrometers in the range –50 °C to 20 °C. Key comparisons outside this dew-point range will be considered in a separate project in future.

Final Report 2008-03-26

The comparison has been finished and the report is available here https://doi.org/10.1088/0026-1394/47/1A/03003,

In this project, a regional key comparison is carried out between European national measurement institutes in the field of humidity. The aim of comparison is to demonstrate equivalence between humidity (dew point) realisations, in support of the CIPM Mutual Recognition Arrangement.
The method of comparison is calibration of dew-point hygrometers in the range –50 °C to +20 °C. Key comparisons outside this dew-point range will be realised in separate projects in future.
The project is realised in three parallel loops. MIKES co-ordinates the comparison and pilots the loop 1. The other two loops are piloted by NMi (loop 2) and METAS (loop3). The loops are linked to each other. Each link consists of two laboratories. Two chilled mirror hygrometers (of the same type) are used as the transfer standards in each loop.

All measurements were completed in January 2008. The Draft B of the Final Report was submitted to the CCT/WG7 in January 2009.

Progress Report 2005-03-15

The method of comparison is calibration of dew-point hygrometers in the range –50 °C to 20 °C. Key comparisons outside this dew-point range will be realised in separate projects in future.

The project is realised in three parallel loops. MIKES co-ordinates the comparison and pilots the loop 1. The other two loops are piloted by NMi (loop 2) and METAS (loop3). The loops are linked to each other. Each link consists of two laboratories. Two chilled mirror hygrometers (of the same type) are used as the transfer standards in each loop.

In 2004, the transfer standards were tested by the pilot laboratories. First laboratories after the pilot laboratories started measurements in the autumn. Since then, delays have been caused by technical problems (with transfer standards and laboratory standards) and problems with ATA Carnet documents. In loops 1 and 2, the places of IPQ, PTB (loop 2) and DELTA (loop 3) in the comparison loop schemes have been changed. The loops 1 and 3 are delayed 3 to 4 months. The delay in the loop 2 is about one month.

Progress Report 2003-04-01

Since the proposal of this project, the number of participants has risen substantially, to 24. An early draft of the measurement protocol has been sent to the participants for comments. Comments have been discussed in the meeting of the EUROMET Humidity Expert Group (31 March 2003) and second draft protocol will be prepared by the coordinator. The project will be realised in three parallel loops. At each loop, two chilled mirror hygrometers (of the same type) will be used as the transfer standards. MBW Elektronik AG is manufacturing the instruments. A batch of PRTs has been tested at INTA. Six of these sensors will be chosen (by the coordinator) to be used in the instruments. The instruments will be tested in autumn 2003 and the comparison measurements will start in spring 2004.

Close liaison is being maintained with the CIPM/CCT Working Group 6 on Humidity Measurements, to ensure that the scope and protocol of the EUROMET intercomparison are consistent with the planned CCT key comparison, so that a clear relationship can be drawn between the results at regional and global levels.

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