a primary flow calibration system for the support of high performance gas flow transfer standards
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A PRIMARY FLOW CALIBRATION SYSTEM FOR THE SUPPORT OF HIGH PERFORMANCE GAS FLOW TRANSFER STANDARDS

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A PRIMARY FLOW CALIBRATION SYSTEM FOR THE SUPPORT OF HIGH PERFORMANCE GAS FLOW TRANSFER STANDARDS. P. Delajoud, M. Bair, C. Rombouts, M. Girard. Introduction. Intensive Extensive. Introduction. DHI offers high performance gas flow transfer standards since 1993

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a primary flow calibration system for the support of high performance gas flow transfer standards

A PRIMARY FLOW CALIBRATION SYSTEM FOR THE SUPPORT OF HIGH PERFORMANCE GAS FLOW TRANSFER STANDARDS

P. Delajoud, M. Bair, C. Rombouts,

M. Girard

NCSLI 2007

introduction
Introduction
  • Intensive
  • Extensive

NCSLI 2007

introduction1
Introduction
  • DHI offers high performance gas flow transfer standards since 1993
  • Requires means to efficiently and reliably calibrate them with very low measurement uncertainty

NCSLI 2007

introduction2
Introduction
  • Product line of high accuracy LFEs
    • Range from 0.02 to 2000 mg/s (1 Ncc min-1 to 100 Nl min-1)
    • Supported by static gravimetric reference and calibration chain
    • Calibration chain is difficult to maintain

NCSLI 2007

introduction3
Introduction
  • 2002 introduced compatible sonic nozzles
    • Ranges from 0.2 to 100 g/s (10 to 5000 Nl min-1)
    • Cannot be supported by static gravimetric reference because they cannot start from zero flow state
    • Excellent repeatability

NCSLI 2007

introduction4
Introduction
  • Simultaneously developed dynamic gravimetric flow standard
    • GFS2102: 0.2 to 200 mg/s (10 to 10000 Ncc min-1)
    • Able to take measurements “on the fly” with flow stabilized
    • Allows calibration of sonic nozzles that cannot start from zero flow
    • Fully automated

NCSLI 2007

introduction5
Introduction
  • Developed extensive measurement technique to “build” traceability to higher flows
    • Technique named “successive addition”
    • Uses very low uncertainty contributed by repeatability from sonic nozzles to extend traceability from 0.1 to 100 g/s (5 to 5000 slm) and higher.
    • Technique also used with LFEs below GFS range.

NCSLI 2007

gfs gravimetric flow standard
GFS Gravimetric Flow Standard
  • Objectives of developement
    • Require less mass depletion to reduce the amount of time necessary to take a point
    • Be able to take gravimetric points “on the fly” without having to remove bottles for weighing
    • Reduce the total uncertainty to a level of ± 5 parts in 104 of reading or better.

NCSLI 2007

gfs gravimetric flow standard1
GFS Gravimetric Flow Standard
  • Description of operation
    • More complete description in the paper
      • The Implementation Of Toroidal Throat Venturi Nozzles To Maximize Precision In Gas Flow Transfer Standard Applications, 2005 FLOMEKO

NCSLI 2007

gfs gravimetric flow standard4
GFS Gravimetric Flow Standard
  • Uncertainties
    • Technical Note 6050TN09 - Complete uncertainty analysis on DHI website of the GFS2102.

NCSLI 2007

gfs gravimetric flow standard5
GFS Gravimetric Flow Standard
  • Uncertainties
    • Uncertainties are low due to the fact that the system will start and stop after flow is stabilized
    • Uncertainties and errors that are constants are tared out and only those that have changed from start readings to subsequent readings are relevant

NCSLI 2007

gfs gravimetric flow standard6
GFS Gravimetric Flow Standard
  • Uncertainties
    • Mass
    • Time
    • Air buoyancy (cylinder)
    • Air buoyancy (regulator)
    • Type A – Contributed by the balance
      • Repeatability, linearity, resolution

NCSLI 2007

gfs gravimetric flow standard7
GFS Gravimetric Flow Standard
  • Uncertainties
    • Rate of change of mass
      • Thought of as resolution due to the ability of the balance to read a mass value
      • For example the balance can only update 23 times per second – If the flow rate is low (0.2mg/s or 10 sccm) resolution is good, if flow rate is high, resolution increases
        • 200mg/s / 23 readings per second = resolution of 8.7 mg; 1 std uncertainty = 2.5 mg

NCSLI 2007

gfs gravimetric flow standard8
GFS Gravimetric Flow Standard
  • Uncertainties
    • Combined uncertainties at different flow rates and depletion totals to derive an equation to use as the “typical flow measurement uncertainty”.
    • ± (3 mg + 0.035 mg/g depletion) + 1.25% of change of mass per second.

NCSLI 2007

flow traceability

Sonic Nozzle Calibration Chain

LFE Calibration Chain

SLM

0.001

10

5000

0.01

direct gravimetric

Flow Traceability

NCSLI 2007

successive addition
Successive Addition
  • Technique for “building” traceability to higher flows
    • Works by taking advantage of extensive property of flow and excellent repeatability of sonic nozzles
      • Less than 0.01% of reading under normal laboratory conditions

NCSLI 2007

successive addition1
Successive Addition
  • Technique for “building” traceability to higher flows
    • All data is traceable through precise multiples of the original reference points of 100 and 200 mg/s.
    • Traceability can come from any point in the test.
    • Sonic nozzles are not affected by downstream changes in pressure as long as they are choked.

NCSLI 2007

successive addition4
Successive Addition
  • Picture of successive addition test

NCSLI 2007

successive addition5
Successive Addition
  • Calibration chain
    • Uses two separate “builds” starting from 100 and 200 mg/s (5 and 10 Nl min-1)
    • Ranges are skipped to allow for optimum BPR

NCSLI 2007

successive addition7
Successive Addition
  • Uncertainties
    • Because of the method used there is no uncertainty due to the linearity of the nozzles in the test.
    • Uncertainties for discharge coefficients determined for each nozzle are evaluated by comparing the two separate “builds” in the calibration chain.

NCSLI 2007

successive addition8
Successive Addition
  • Uncertainties
    • Original reference flow from the GFS
    • Transfer point pressure
    • Transfer point temperature
    • Repeatability of the test (Type A)

NCSLI 2007

successive addition9
Successive Addition
  • Uncertainties

NCSLI 2007

successive addition10
Successive Addition
  • Successive addition run backwards
    • Needed method of traceability to cover range below 0.2 mg/s (10 sccm).
    • Used laminar molblocs in one successive addition run to define flows down to 2.5 sccm.
    • More uncertainty because of less repeatability by LFEs.

NCSLI 2007

flow traceability1

Sonic Nozzle Calibration Chain

LFE Calibration Chain

SLM

0.001

5

10

5000

0.01

direct gravimetric

successive addition

Flow Traceability

NCSLI 2007

verification of traceability and uncertainty
Verification of Traceability and Uncertainty
  • GFS evaluated by comparison with existing static gravimetric reference
    • Performed at points for optimum uncertainty for static reference and LFEs used in the test
    • Since they are independent agreement must be inside of RSS of uncertainties

NCSLI 2007

verification of traceability and uncertainty1
Verification of Traceability and Uncertainty
  • Comparisons – 2ea 1E2 LFE’s at 2 mg/s (100 Ncc min-1)

NCSLI 2007

verification of traceability and uncertainty2
Verification of Traceability and Uncertainty
  • Calibration Chain verification
    • Comparison between two separate successive addition builds
    • External verification through calibration of sonic nozzle by DHI and CEESI in May 2005 using 1E4-S at various flows

NCSLI 2007

conclusion
Conclusion
  • With this system of traceability
    • Automation of GFS and ability to perform low mass depletions allows for an abundance of gravimetric data
    • Complete calibrations may be performed hands free for sonic nozzles
    • Uncertainties are low due to ability to measure “on the fly”

NCSLI 2007

conclusion1
Conclusion
  • With this system of traceability
    • Successive addition eliminates uncertainty from the linearity of nozzles and primarily depends on repeatability
    • Range is only limited by support equipment to transport gas and availability of higher ranges of sonic nozzles

NCSLI 2007

slide40

Thank you …

NCSLI 2007

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