Performance and Validation Tests on the NIST Hybrid Humidity Generator

Meyer, Christopher W.; Miller, W Wyatt; Ripple, Dean C.; Scace, Gregory E.

doi:10.1007/s10765-007-0342-4

Cited by 13 publications

(9 citation statements)

References 5 publications

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“…In an effort to allow the low-temperature calibration of radiosondes specialized in upper-air measurement, MIKES in Finland developed a UTHC (Sairanen et al, 2015) that met the uncertainty requirement of the GRUAN which is 2 % in terms of the mixing ratio. Its UTHC was based on a hybrid humidity generator principle (Mayer et al, 2008), in which the carrier gas passing through a saturator and a zero gas supplier mixed in a controlled way for the humidity generation. In this regard, it allows a fast humidity change by controlling the mixing ratio and thus can be useful for studying dynamic responses of humidity sensors in addition to the calibration at static states.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of radiosonde humidity sensors at low temperature using ultralow-temperature humidity chamber

et al. 2018

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Abstract. Accurate measurements of temperature and water vapor in the upper-air are of great interest in relation to weather prediction and climate change. Those measurements are mostly conducted using radiosondes equipped with a variety of sensors that are flown by a balloon up to lower stratosphere. Reference Upper Air Network (GRUAN) has identified water vapor pressure as one of the most important measurands and has set an accuracy requirement of 2 % in terms of the mixing ratio. In order to achieve the requirement, many errors in the humidity measurement such as a temperature dependency in sensing characteristics including measurement values and response time need to be corrected because humidity sensors of radiosondes pass through low-pressure (1 kPa) and low-temperature (−80 ∘C) environments in the upper-air. In this paper, the humidity sensing characteristics of Jinyang radiosonde sensors in relation to temperature dependencies were evaluated at low temperature using a newly developed ultralow-temperature humidity chamber. The sensitivity characteristic curve of the radiosonde sensors was evaluated down to −80 ∘C, and the calibration curves of the humidity sensor and the temperature sensor were obtained. The response time of humidity sensor slowly increased from 52 to 116 s at the temperature from 20 to −40 ∘C, respectively, and then rapidly increased to almost one hour at −80 ∘C. Those results will help to improve the reliability of the upper-air observation data.

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Section: Introductionmentioning

confidence: 99%

Evaluation of radiosonde humidity sensors at low temperature using ultralow-temperature humidity chamber

et al. 2018

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“…Die im Beitrag aufgeführten Ergebnisse belegen, dass mit dem neu entwickelten Kalibriergasgenerator Flüssigkeiten mit hoher absoluter Genauigkeit und Langzeitstabilität verdunstet werden können. Systeme, mit denen eine vergleichbare Absolutgenauigkeit und zeitliche Stabilität der eingestellten Dampfpartialdrücke erreicht wird, sind bislang nur für Wasserdampf bekannt und werden vor allem bei Referenzinstituten für die Überprüfung von Feuchtesensoren betrieben [11,12]. Durch die Wahl von Duranglas, Edelstahl und Perfluorokunststoffen als medienberührte Materialien ist der Kalibriergasgenerator für die Verdunstung einer Vielzahl flüssiger Gemische einsetzbar.…”

Section: Diskussionunclassified

1.3 - Kalibriergasgenerator mit coulometrischer Überwachung

Zosel¹,

Müller²,

Novak³

et al. 2022

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“…The NIST Hybrid Humidity Generator (HHG) [1][2][3] provides calibration services for a variety of humidity-measuring instruments. It is operated by the Thermodynamic Metrology Group of the Sensor Science Division, which is part of the Physical Measurement Laboratory.…”

Section: Overview Of the Calibration Servicementioning

confidence: 99%

Calibration of hygrometers with the hybrid humidity generator

Meyer¹,

Hodges²,

Huang³

et al. 2021

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We describe here the calibration of customer hygrometers using the NIST Hybrid Humidity Generator (HHG). This generator produces humidified air with water amount fractions (water mole fractions) ranging from 1.0 10?7 to 0.57 using calibration gas flows up to 150 standard liters per minute. At ambient pressure these amount fractions correspond to dew/frost points ranging from 90 C to +85 C. The HHG may be used to calibrate instruments measuring water amount fraction, such as cavity ring-down hygrometers. It may also be used to calibrate chilled-mirror hygrometers measuring dew/frost-point temperature when an additional pressure measurement is made at the inlet of the hygrometer. Finally, the HHG may be used to provide humidified air for the calibration of relative humidity sensors in a temperature-controlled test chamber; for this, an additional temperature measurement is made in the chamber. These sensors may be calibrated over the range 2 % to 98 % for temperatures between ?34 C and 85 C. The HHG combines the two-pressure and divided-flow humidity generation methods (hence the name hybrid ). The centerpiece of the HHG is a heat exchanger/saturator that is immersed in a temperature-controlled bath stable to within 1 mK. For dew/frost-point temperatures that are above 10.3 C, the two-pressure method is employed. For frost points at or below 10.3 C, the water-vapor/air mixture is produced by mixing metered streams of moist air produced by the two-pressure method with purified, dry air. In this special publication, we describe the design of the generator and its test chamber. We also describe a series of performance and validation tests on the HHG and its test chamber and use the results of these to construct an uncertainty budget for the generator when used in two-pressure mode and when used in the divided-flow mode. These tests include measurements of temperature gradients and pressure stability in the generator under various operating conditions, and comparison of the humidity generated by the HHG to that generated or measured by the other NIST humidity standards. For dew/frost-point temperatures, the uncertainty budget yields a total expanded uncertainty (k = 2) of less than 0.025 C for dew/frost-point temperatures above 60 C. For amount fraction, the budget yields a total expanded relative uncertainty of less than 0.2 % for amount fractions above 2 10?5. For relative humidity in the test chamber, the budget yields a total expanded relative uncertainty of less than 0.3 %.

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Performance and Validation Tests on the NIST Hybrid Humidity Generator

Cited by 13 publications

References 5 publications

Evaluation of radiosonde humidity sensors at low temperature using ultralow-temperature humidity chamber

Evaluation of radiosonde humidity sensors at low temperature using ultralow-temperature humidity chamber

1.3 - Kalibriergasgenerator mit coulometrischer Überwachung

Calibration of hygrometers with the hybrid humidity generator

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