High-range dew-point temperature realization using two-pressure generators

Project Description

The final goal is to provide INTA with a new standard that covers the dew point temperature range from -27 to 90 °C with a gas flow up to 5 l/min in the "two-pressure" mode, extended to 95 °C when operated as a continuous flow "single-pressure" generator, and investigation of the importance of the enhancement factors in the uncertainty estimations used in support of the participants CMC's. This contribution is to be investigated in several designs of saturators available at the partner institutions.The collaboration project comprises the following stages:

  •  Comparison of the existing INTA and BEV/E E generators using a precision optical dew point hygrometer as a transfer standard over the range -10 °C to 75 °C, and the characterization of the transfer standard over the full range at BEV/E E.
  •  The supply of INTA of the main components of a new humidity generator, of the same basic design as the BEV/E E existing generator and providing assistance in the assembly and characterization of the unit by INTA.
  •  Comparison of the two INTA generators using two transfer standards over their common range, followed by measurements on the new generator up to the new extended upper limit.
  •  Repeated measurements at BEV/E E over the full range to ensure the long-term stability of the transfer standard during the project and establishing the new INTA Calibration Measurement Capability based on the new generator.
  •  Detailed investigation of the influence of the enhancement factors on the uncertainty assigned to two-pressure standard humidity generators.

Final Report 2018-03-16

The objectives of the project have been achieved in full. The E+E designed generator has been successfully implemented at INTA and has been used extensively in the characterization of transfer standards in the frost/dew point temperature range from -20 ºC to 95 °C. The protocol for CCT-K8 was further refined with the technique for correct flow-rate and pressure drop determination to ensure reproducibility of measurements, developed and published. It has been shown bilaterally that the two realizations at BEV/E+E and INTA are equivalent to within the reproducibility of the transfer standards at the state-of-the-art level. Studies of the determination and influence of the enhancement factors up to 1 MPa have also been performed.

Progress Report 2017-04-14

Measurement techniques have continued to be developed. Extensive characterization of the INTA high-range optical dew-point hygrometer have been performed on the standard humidity generators in both two-pressure and single pressure modes in the range from -10 °C to +95 °C. The long-term stability of the hygrometer has been investigated and the combined reproducibility of the generators and hygrometer evaluated. Valuable information was obtained for inclusion in the CCT-K8 protocol.

Progress Report 22.02.2016

Further work has been carried out with the generators both in single and two-pressure modes with the INTA transfer standard has been performed regularly.

Progress Report 2015-02-21

Optimisation of the procedure to materialize dew-point temperature using the high-temperature standard humidity generator led to an improvement in the combided reproductibility of the generator and transfer standards at the 95 ºC limit. A comparsion of the results obtained by both laboratories on an MBW 373HX transfer standard SN: 06-1112 in the dew-point temperature range from 1 ºC to 95 ºC was performed. The differences observed were in the range 1 mK to 13 mK. The expanded uncertainty of each laboratory is between 35 mK and 50 mK. This result also validated the procedure for the flow settings at the high levels. Masurements at E+E and INTA were performed with the measurement head at 108 kPa and 101.3 KPa, respectively.

Progress Report 2009-04-01

The main components of the humidity generator were supplied to INTA and the generator was assembled at INTA and compared both with the existing Spanish national humidity standards generator from -10 °C to 75 °C in two-pressure mode and with the BEV/E E generator from -10 °C to 90 °C, using precision optical dew point hygrometers as transfer standards over the range -10 °C to 75 °C.

The results of this work so far have been published as R. Benyon & H. Mitter, "The New INTA High-Range Standard Humidity Generator and its Comparison with the Austrian National Humidity Standard Maintained at BEV/E E", Int J Thermophys (2008) 29:1623-1631.
The previous work was performed with water as the bath fluid. A new bath, to be used with a high-temperature inert bath fluid, has been acquired and the generator is being re-assembled prior to a complete new characterization over the full range in both two-pressure mode and single pressure mode, to commence the detailed investigation of the influence of the enhancement factors on the uncertainty assigned to two-pressure standard humidity generators.

Thermometry (T)
Helmut Mitter, BEV/E+E (Austria)
Coordinating Institute
INTA (Spain)
Participating Partners
BEV/E+E (Austria)