Carroll, P A; Bell, S A; Stevens, M (2015) A calibration facility for dew point in air up to 1 Mpa. Int. J. Thermophysics, 36 (12). pp. 3453-3465.

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Abstract

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 vapour enhancement factor) is well enough known at moderate pressures, but there remains a need to characterise 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 60 °C to +10 °C, at pressures up to 1 MPa (10 bar), has been validated and is now accredited for the calibration of hygrometers. The expanded uncertainty of the dew-point generator in this range with a coverage factor k = 2 is ± 0.07 ºC.

Item Type:	Article
Keywords:	humidity, pressure, dew point
Subjects:	Engineering Measurements Engineering Measurements > Thermal
Identification number/DOI:	10.1007/s10765-015-1984-2
Last Modified:	02 Feb 2018 13:13
URI:	https://eprintspublications.npl.co.uk/id/eprint/6919