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A Calibration Facility for Dew Point in Air up to 1 MPa


The provision of primary dew-point standards for humidified air and nitrogen at atmospheric pressure is well established, and measurement traceability to these standards provides confidence in a vast number of air humidity measurements. However, hygrometers are used industrially at a wide range of pressures. Both the performance of hygrometers and the properties of humid gases are known to vary with gas pressure. The pressure-dependence of gas non-ideality for air–water mixtures (water-vapor enhancement factor) is well enough known at moderate pressures, but there remains a need to characterize hygrometers at the pressure of use. To address this, a humidity calibration capability of wider scope is under development at the UK National Physical Laboratory (NPL). As an initial stage in the development of this capability, a humidity standard generating air or nitrogen in the dew-point range from \(-60\,^{\circ }\hbox {C}\) to \(+10\,^{\circ }\hbox {C}\), at pressures up to 1 MPa (10 bar) has been validated for the calibration of hygrometers. The expanded uncertainty of the dew-point generator in this range with a coverage factor \(k= 2\) is \(\pm 0.07\,^{\circ }\hbox {C}\).

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  1. M. Stevens, S.A. Bell, Meas. Sci. Technol. 3, 943 (1992)

    Article  ADS  Google Scholar 

  2. M. Stevens, in Proceedings of TEMPMEKO ’99, 7th International Symposium on Temperature and Thermal Measurements in Industry and Science, ed. by J.F. Dubbeldam, M.J. de Groot (Edauw Johannissen bv, Delft, 1999), pp. 191–196

  3. S. Hasegawa, J.W. Little, J. Res. Natl. Bur. Stand. (U.S.) 81A, 1 (1977)

    Article  Google Scholar 

  4. A. Actis, M. Banfo, V.C. Fernicola, R. Galleano, S. Merlo, in Papers and Abstracts from the Third International Symposium on Humidity & Moisture, vol. 1, ed. by S.A. Bell (NPL, London, 1998), pp. 2–9

  5. C.C.M. Luijten, M.E.H. van Dongen, L.E. Stormbom, Sens. Actuators B-Chem 49, 279 (1998)

    Article  Google Scholar 

  6. D. Sonntag, Z. Meteorol. 70, 340 (1990)

    Google Scholar 

  7. R. Bosma, D. Mutter, A. Peruzzi, Metrologia 49, 597 (2012)

    Article  ADS  Google Scholar 

  8. BIPM, Evaluation of Measurement Data—Guide for the Expression of Uncertainty in Measurement, JCGM, vol. 100 (2008), Accessed 2 Sept 2015

  9. UKAS M3003. The Expression of Uncertainty and Confidence in Measurement, Edition 3 (November 2012), Accessed 14 Jan 2015

  10. C.W. Meyer, J.T. Hodges, P.H. Huang, W.W. Miller, D.C. Ripple, G.E. Scace, NIST Spec. Pub. 250-83 (2008)

  11. R. Hardy, in Papers and Abstracts from the Third International Symposium on Humidity and Moisture, vol. 1, ed. by S.A. Bell (NPL, London, 1998), pp. 214–222

  12. M. Heinonen, M. Anagnostou, S.A. Bell, M. Stevens, R. Benyon, R.A. Bergerud, J. Bojkovski, R. Bosma, J. Nielsen, N. Böse, P. Cromwell, A. Kartal Dogan, S. Aytekin, A. Uytun, V. Fernicola, K. Flakiewicz, B. Blanquart, D. Hudoklin, P. Jacobson, A. Kentved, I. Lóio, G. Mamontov, A. Masarykova, H. Mitter, R. Mnguni, J. Otych, A. Steiner, N. Szilágyi Zsófia, D. Zvizdic, Int. J. Thermophys. 33, 1422 (2012)

    Article  ADS  Google Scholar 

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This work was supported by the UK National Measurement System Programme for Engineering and Flow Metrology. The authors gratefully acknowledge the help of Thunder Scientific Corporation for modifications to the humidity generator.

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Correspondence to P. A. Carroll.

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Carroll, P.A., Bell, S.A. & Stevens, M. A Calibration Facility for Dew Point in Air up to 1 MPa. Int J Thermophys 36, 3453–3465 (2015).

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  • Calibration
  • Dew point
  • Humidity
  • Pressure