Comparison of the realisations of the relative humidity in the range from 10% to 95% at temperatures from -40 °C to 20 °C

Project Description

Four relative humidity transmitters are available for use in the comparison in two loops, each containing two instruments to be measured simultaneously. The two loops will be decided by the participants either on transportation/customs or technical criteria.


Progress Report 2019-04-30

No further work has been possible since the last report due to unavoidable commitments at INTA. Expected to resume is the second quarter of 2019.

Progress Report 2018-03-16

Extensive experimental work necessary for the completion of the measurement protocol has been performed. The preconditioning procedure and number of cycles necessary to obtain the optimum performance of the transfer standards has been detertmined for all instruments. A new special nickel-plated brass chamber has been designed and constructed at E+E and characterized to determine performance down to -40 ºC at the lowest frost-point temperature. It is expected that the protocol can be submitted to the participants and to CCT-WG-KC in time to launch the comparison in 2018-3Q with two loops of one E+E and one VAISALA probe each. Measurements are to be perfomed at (+1, -40, -20 and +1) ºC at nominal RH: (0, 10/15, 50, 90/95) in standard RH.


Progress Report 2017-04-14

Extensive characterization of the transfer standards has been performed in order to establish the behaviour of the instruments after the purging cycle and to establish preconditioning procedures in the protocol to ensure optimum reproducibility. The two E+E transmitters have been substituted for models without the external temperature probe to enable the simultaneous measurement of the four instruments for the reference measurements and after suggestions from the participants. It is expected that the protocol can be finalized and the comparison launched in the Autumn of 2017 with two loops to reduce the total time of the comparison.


Progress Report 2016-02-22

Four relative humidity transmitters (E+E and VAISALA) have been provided by the manufacturers for use in the comparison. Comparison delayed due to problems at the coordinating laboratory, now resolved.