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Search Publications by: James W. Schmidt (Assoc)

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Displaying 1 - 25 of 34

Dynamic Measurement of Gas Flow using Acoustic Resonance Tracking

March 21, 2023
Author(s)
Jodie Gail Pope, Keith A. Gillis, James W. Schmidt
We measured gas flows exiting large, un-thermostated, gas-filled, pressure vessels by tracking the time-dependent pressure P(t) and resonance frequency fN(t) of an acoustic mode N of the gas remaining in each vessel. This is a proof-of-principle

CCM Key Comparison in the Pressure Range 0.05 MPa to 1 MPa (Gas Medium, Gauge Mode) - Phase A1: Dimensional Measurements and Calculation of Effective Area

October 12, 2021
Author(s)
G F. Molinar, B Rebaglia, A Sacconi, J C. Legras, G P. Vailleau, James W. Schmidt, John R. Stoup, D R. Flack, Waldimir Sabuga, O Jusko
The results obtained by five laboratories in the determination of the effective areas of two gas-operated 10 cm 2 piston-cylinder assemblies from dimensional measurements carried out as part, called phase A1, of a key comparison in the pressure range 0.05

Reproducibility of Liquid Micro-Flow Measurements

June 26, 2019
Author(s)
John D. Wright, James W. Schmidt
New applications in biology, medicine, and manufacturing require reliable measurements of liquid flows smaller than 100 υL/min. NIST addressed this requirement by improving the reliability and ease of use of NIST’s Dynamic Gravimetric Micro-Flow Standard

Microparticle tracking velocimetry as a tool for microfluidic flow measurements

June 7, 2017
Author(s)
Paul NMN Salipante, Steven D Hudson, James W. Schmidt, John D. Wright
The accurate measurement of flows in microfluidic channels is important for commercial and research applications. We compare the accuracy of flow measurement techniques over a wide range flows. Flow measurements made using holographic microparticle

Measuring collected gas with microwave and acoustic resonances

April 23, 2015
Author(s)
Keith A. Gillis, James W. Schmidt, Michael R. Moldover, James B. Mehl
With calibrations of large flow meters in mind, we established the feasibility of determining the mass M of argon gas contained within a 0.3 m 3 commercially manufactured pressure vessel ("tank") with a relative standard uncertainty of u r(M) = 0.0016 at 0

Micro-Flow Calibration Facility at NIST

April 15, 2015
Author(s)
James W. Schmidt, John D. Wright
The Fluid Metrology Group (FMG) at NIST is developing a primary, dynamic gravimetric liquid flow standard for use in the range 1 mL/min to 100 nL/min (and eventually lower). An elevated reservoir of water with a pressure head of a few centimeters provides

"Weighing" a Gas With Microwave and Acoustic Resonances

March 24, 2015
Author(s)
Keith A. Gillis, James B. Mehl, James W. Schmidt, Michael R. Moldover
With calibrations of large flow meters in mind, we established the feasibility of determining the mass Mof argon gas contained within a 0.3 m 3 commercially manufactured pressure vessel ("tank") with a relative uncertainty of u r(M) = 0.0015 at 0.6 MPa by

Microwave Determination of the Volume of a Pressure Vessel

December 9, 2014
Author(s)
Michael R. Moldover, James W. Schmidt, Keith A. Gillis, James B. Mehl, John D. Wright
Using microwave techniques that are scalable to very large volumes, we measured the interior volume of a 0.3 m 3, commercially-manufactured, pressure vessel with an uncertainty of 0.05 %, as confirmed by independent, more-accurate, gas-expansion

Reference measurements of Hydrogen's Dielectric Permittivity

August 10, 2009
Author(s)
James W. Schmidt, Michael R. Moldover, Eric F. May
We used a quasi-spherical cavity resonator to measure the relative dielectric permittivity ε r of H 2 at frequencies from 2.4 GHz to 7.3 GHz, at pressures up to 6.5 MPa, and at the temperatures 273 K and 293 K. The resonator was calibrated using auxiliary

The Polarizability of Helium and Gas Metrology

June 22, 2007
Author(s)
James W. Schmidt, R Gavioso, E May, Michael R. Moldover
Using a quasi-spherical, microwave cavity resonator, we measured the refractive index of helium to deduce its molar polarizability A ε in the limit of zero density. We obtained (A ε,meas - A ε,theory)/A ε = (-1.8plus or minus} 8.4)× 10 -6, where the

Capacitors and Electromagnetic Resonators for Gas Metrology

May 1, 2007
Author(s)
Michael R. Moldover, James W. Schmidt
Gas-filled capacitors are being used as primary thermometers and they show promise as primary pressure standards and for measuring the Boltzmann constant. With these metrological applications in mind, we discuss the advantages and disadvantages of audio

A Primary Dead-Weight Tester for Pressures (0.05-1.0) MPa

April 1, 2003
Author(s)
K. Jain, Walter J. Bowers Jr., James W. Schmidt
Recent advances in technology on two fronts, 1) the fabrication of large diameter pistons and cylinders with good geometry, and 2) the ability to measure the dimensions of these components with high accuracy, have allowed dead-weight testers at NIST to

Dielectric Permittivity of Eight Gases Measured with Cross Capacitors

March 1, 2003
Author(s)
James W. Schmidt, Michael R. Moldover
A 4-ring, toroidal cross capacitor was used to measure accurately the relative dielectric permittivity ε(p,T) of He, Ar, N 2, O 2, CH 4, C 2H 6, C 3H 8, and CO 2. (ε is often called the dielectric constant. ) The data are in the range from 0 C to 50 C and

A Double-Primary Dead-Weight Tester for Pressures (35-175) kPa in Gage Mode

February 1, 2003
Author(s)
K. Jain, Y Q. Cen, Walter J. Bowers Jr., James W. Schmidt
Primary pressure standards in the atmospheric pressure range are often established using mercury manometers. Less frequently, controlled-clearance dead-weight testers in which one component (normally the piston) has been dimensionally measured have also

NCSL Pressure Comparison At 0.69 Mpa (100 psi) and 1.4 Mpa (200 psi)

July 1, 2000
Author(s)
Robert G. Driver, James W. Schmidt
The pressure and Vacuum Group at NIST has piloted a pressure comparison under the auspices of the Measurement comparison program committee for the NCSL. A 1.4 MPa (~200 psi)transducer package used as a transfer standard was circulated among 20 domestic

A primary pressure standard at 100 kPa

June 1, 1999
Author(s)
James W. Schmidt, Y Q. Cen, Robert G. Driver, Walter J. Bowers Jr., J C. Houck, S A. Tison, Charles D. Ehrlich
Primary pressure standards in the atmospheric pressure range are often established using mercury manometers. To a lesser extent controlled-clearance dead-weight testers in which one component (normally the piston) has been dimensionally measured have also