A gas pressure scale based on primary standard piston gauges

Olson, Douglas A.; Driver, Robert G.; Bowers, Walter J.

doi:10.6028/jres.115.027

Cited by 7 publications

(5 citation statements)

References 10 publications

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“…Additionally, the manual control method in which the gas flowed into the system, which used a valve that was slowly opened vs the constant 0.16 Pa m 3 s −1 , may have impacted the peak temperatures. The TFPRTs were taken (15)(16)(17)(18)(19)(20) s apart due to bridge integration time, however as seen in figure 8, the two measurements of PRT1 bracketing the PRT2's peak value are at least 1.5 times larger than the peak PRT2 measurement. This indicates that some spatial gradients exist across the glass cavity.…”

Section: Discussionmentioning

confidence: 99%

“…Helium is the best gas due to its direct link via quantum calculations [9], however helium gas has lower sensitivity to temperature change, larger uncertainty due to impurities/outgassing, and is subject to systematic uncertainties due to its ability to absorb into the glass cell [19]. The optical RIGT was tested using nitrogen with the pressure applied using a piston gauge which can generate a pressure with a stability better than 1 μPa Pa −1 at atmospheric pressure and can measure pressure to better than 5 μPa Pa −1 [20]. In order to account for any thermal expansion of the glass, the FLOC must be pumped out to vacuum (<1 mPa) to measure the initial frequency ( f Bi ) which is subtracted from all frequency measurements at pressure.…”

Section: Optical Thermometer Designmentioning

confidence: 99%

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Transient heating in fixed length optical cavities for use as temperature and pressure standards

et al. 2021

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Optical refractometry techniques enable realization of both pressure and temperature directly from properties of the gas. The NIST refractometer, a fixed length optical cavity (FLOC) has previously been evaluated for operation as pressure standard, and now in this paper, is evaluated for the feasibility of operation as a primary temperature standard as well. The challenge is that during operation, one cavity is filled with gas. Gas dynamics predicts that this will result in heating which in turn will affect the cavity temperature uniformity, impeding the ability to measure the gas temperature with sufficient accuracy to make the standard useful as a primary standard for temperature or pressure. Temperature uniformity across the refractometer must be less than 0.5 mK for measurements of the refractivity to be sufficiently accurate for the FLOC. This paper compares computer modeling to laboratory measurements, enabling us to validate the model to predict thermal behavior and to accurately determine the measurement uncertainty of the technique. The results presented in this paper show that temperature of the glass elements of the refractometer and ‘thermal-shell’ copper chamber are equivalent to within 0.5 mK after an equilibration time of 3000 s (when going from 1 kPa to 100 kPa). This finding enables measurements of the copper chamber to determine the gas temperature to within an uncertainty (k = 1) of 0.5 mK. Additionally, the NIST refractometer is evaluated for feasibility of operation as temperature standard.

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Section: Discussionmentioning

confidence: 99%

Section: Optical Thermometer Designmentioning

confidence: 99%

Transient heating in fixed length optical cavities for use as temperature and pressure standards

et al. 2021

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“…/ = × and a formula proposed in [4] to interpolate numerical values of G P for planar channel leads to is the slip coefficient [24]. The expression (16) has been obtained under the assumption of the diffuse gas-surface interaction that is the complete accommodation. As was shown in [21], the Poiseuille coefficient is affected by the tangential momentum accommodation coefficient (TMAC) t α .…”

Section: Methods Of Calculationmentioning

confidence: 99%

“…At the moment, its relative standard uncertainty is estimated as 3 10 6 × − . The information about this PCA can be found in [3,9,16]. The aim of the present work is to revise the effective area for PG39 applying numerical results of rarefied gas flow [12] obtained previously on the basis of the kinetic Boltzmann equation.…”

Section: Introductionmentioning

confidence: 99%

Primary pressure standard based on piston-cylinder assemblies. Calculation of effective cross sectional area based on rarefied gas dynamics

et al. 2016

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Currently, the piston-cylinder assembly known as PG39 is used as a primary pressure standard at the National Institute of Standards and Technology (NIST) in the range of 20 kPa to 1 MPa with a standard uncertainty of 3 10 6 × − as evaluated in 2006. An approximate model of gas flow through the crevice between the piston and sleeve contributed significantly to this uncertainty. The aim of this work is to revise the previous effective cross sectional area of PG39 and its uncertainty by carrying out more exact calculations that consider the effects of rarefied gas flow. The effective cross sectional area is completely determined by the pressure distribution in the crevice. Once the pressure distribution is known, the elastic deformations of both piston and sleeve are calculated by finite element analysis. Then, the pressure distribution is recalculated iteratively for the new crevice dimension. As a result, a new value of the effective area is obtained with a relative difference of 3 10 6 × − from the previous one. Moreover, this approach allows us to reduce significantly the standard uncertainty related to the gas flow model so that the total uncertainty is decreased by a factor of three.

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“…The pressure stabilization scheme employed in our work exploits a piston gauge in two novel ways. Piston gauges (PGs) are traditionally used as primary and secondary pressure standards in national metrology institutes [12][13][14][15][16][17]. To achieve long-term pressure stability, many researchers first calibrate a pressure transducer using a piston pressure balance, then use the calibrated gauge output as the input for a pressure control feedback loop [18][19][20][21].…”

Section: Introductionmentioning

confidence: 99%

Realization of ppm level pressure stability for primary thermometry using a primary piston gauge

et al. 2020

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To achieve an uncertainty of 0.25 mK in single-pressure refractive-index gas thermometry (SPRIGT), the relative pressure variation of He-4 gas in the range 30 kPa to 90 kPa, should not exceed 4 ppm (k=1). To this end, a novel pressure control system has been developed. It consists of two main parts: a piston gauge to control the pressure, and a home-made gas compensation system to supplement the micro-leak of the piston gauge. In addition, to maintain the piston at constant height, a servo loop is used that automatically determines in real time the amount of extra gas required. At room temperature, the standard deviations of the stabilized pressure are 3.0 mPa at 30 kPa, 4.5 mPa at 60 kPa and 2 mPa at 90 kPa. For the temperature region 5 K-25 K used for SPRIGT in the present work, the relative pressure stability is better than 0.16 ppm i.e. 25 times better than required. Moreover, the same pressure stabilization system is readily transposable to other primary gas thermometers.

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A gas pressure scale based on primary standard piston gauges

Cited by 7 publications

References 10 publications

Transient heating in fixed length optical cavities for use as temperature and pressure standards

Transient heating in fixed length optical cavities for use as temperature and pressure standards

Primary pressure standard based on piston-cylinder assemblies. Calculation of effective cross sectional area based on rarefied gas dynamics

Realization of ppm level pressure stability for primary thermometry using a primary piston gauge

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