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

NCSLI 2007

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

Intensive Extensive

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Introduction

DHI offers high performance gas flow transfer standards since 1993

Requires means to efficiently and reliably calibrate them with very low measurement uncertainty

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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

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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

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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

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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.

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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.

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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

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Uncertainties• Technical Note 6050TN09 - Complete

uncertainty analysis on DHI website of the GFS2102.

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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

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Uncertainties• Mass

• Time

• Air buoyancy (cylinder)

• Air buoyancy (regulator)

• Type A – Contributed by the balance Repeatability, linearity, resolution

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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

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GFS Uncertainties mass flow rate 0.2 mg/s mass flow rate 0.2 mg/s

5 gram depletion 10 gram depletion

Uncertainties Ux - k=1 Sensitivity

Um (correlated)

Um (uncorrelated) Ux - k=1 Sensitivity

Um (correlated)

Um (uncorrelated)

(uncorrelated) [mg/Ux] [mg] [mg] [mg/Ux] [mg] [mg]

Time 0.00005 5000 0.25 0.00005 10000 0.50

Reference cylinder temperature 1.5 0.02 0.03 1.5 0.02 0.03

Ambient temperature reference cylinder 0.11 6.5 0.72 0.11 6.5 0.72

Reference mass buoyancy - temperature 0.05 1.12 0.06 0.05 1.12 0.06

Ambient temperature regulator assembly 0.11 0.46 0.05 0.11 0.46 0.05

Gas properties 0.000006 1559 0.01 0.000006 1559 0.01

Resolution 0.03 1 0.03 0.03 1 0.03

Balance Linearity 0.19 1 0.19 0.19 1 0.19

Repeatability 0.24 1 0.24 0.24 1 0.24

(correlated)

Ambient pressure reference cylinder 29 0.040 1.16 29 0.040 1.16

Ambient pressure regulator assembly 29 0.0012 0.03 29 0.0012 0.03

Reference mass buoyancy - pressure 29 0.0030 0.09 1.28 29 0.0030 0.09 1.28

Ambient humidity reference cylinder 1.7 0.17 0.29 1.7 0.17 0.29

Ambient humidity regulator assembly 1.7 0.020 0.03 1.7 0.020 0.03

Reference mass buoyancy - humidity 1.7 0.026 0.04 0.37 1.7 0.026 0.04 0.37

mass flow rate [mg/s]

Sensitivity [mg/(mg/s)] Um [mg]



Rate of change of mass 0.2 0.0125 0.00 0.2 0.0125 0.00

Combined 0.031% rdg 1.57 mg 0.016% rdg 1.63 mg

Combined and expanded 0.063% rdg 3.13 mg 0.033% rdg 3.25 mg

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GFS Uncertainties mass flow rate 200 mg/s mass flow rate 200 mg/s

20 gram depletion 50 gram depletion

Uncertainties Ux - k=1 SensitivityUm

(correlated)Um

(uncorrelated) Ux - k=1 SensitivityUm

(correlated)Um

(uncorrelated)

(uncorrelated) [mg/Ux] [mg] [mg] [mg/Ux] [mg] [mg]

Time 0.00005 20000 1.00 0.00005 50000 2.50

Reference cylinder temperature 1.5 0.02 0.03 1.5 0.02 0.03

Ambient temperature reference cylinder 0.11 6.5 0.72 0.11 6.5 0.72

Reference mass buoyancy - temperature 0.05 1.12 0.06 0.05 1.12 0.06

Ambient temperature regulator assembly 0.11 0.46 0.05 0.11 0.46 0.05

Gas properties 0.000006 1559 0.01 0.000006 1559 0.01

Resolution 0.03 1 0.03 0.03 1 0.03

Balance Linearity 0.19 1 0.19 0.19 1 0.19

Repeatability 0.24 1 0.24 0.24 1 0.24

(correlated)

Ambient pressure reference cylinder 29 0.040 1.16 29 0.040 1.16

Ambient pressure regulator assembly 29 0.0012 0.03 29 0.0012 0.03

Reference mass buoyancy - pressure 29 0.0030 0.09 1.28 29 0.0030 0.09 1.28

Ambient humidity reference cylinder 1.7 0.17 0.29 1.7 0.17 0.29

Ambient humidity regulator assembly 1.7 0.020 0.03 1.7 0.020 0.03

Reference mass buoyancy - humidity 1.7 0.026 0.04 0.37 1.7 0.026 0.04 0.37





Rate of change of mass 200 0.0125 2.50 200 0.0125 2.50

Combined 0.016% rdg 3.11 mg 0.008% rdg 3.86 mg

Combined and expanded 0.031% rdg 6.21 mg 0.015% rdg 7.72 mg

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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.

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Flow Traceability

LFE Calibration Chain

Sonic Nozzle Calibration Chain

10SLM

0.0010.01

5000

direct gravimetric

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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

Successive Addition

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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.

Successive Addition

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Calchain molbloc-S Working Std molbloc-S

2E1-S (20 sccm/kPa)

1E2-S (100 sccm/kPa) 1E2-S (100 sccm/kPa)

GFS 10 slm point

2E1-S (20 sccm/kPa)

Successive Addition

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2E1-S (20 sccm/kPa)

1E2-S (100 sccm/kPa) 1E2-S (100 sccm/kPa)

GFS 10 slm point

2E1-S (20 sccm/kPa)

Flow Pnt

Comparison (Value is range in

sccm/kPa)

Nom Prs Upstream

(kPa)

Nom Prs Downstream

(kPa)BPR

Upstream5 20(1) + 20(2) = 100(1) 125 50 0.45 20(1) = 100(1) 250 50 0.25 20(2) = 100(1) 250 50 0.210 20(1) + 20(2) = 100(1) 250 100 0.410* 20(1) = 100(1) 500 100 0.210* 20(2) = 100(1) 500 100 0.220 20(1) + 20(2) = 100(1) 500 200 0.4

5 20(1) + 20(2) = 100(2) 125 50 0.45 20(1) = 100(2) 250 50 0.25 20(2) = 100(2) 250 50 0.210 20(1) + 20(2) = 100(2) 250 100 0.410* 20(1) = 100(2) 500 100 0.210* 20(2) = 100(2) 500 100 0.220 20(1) + 20(2) = 100(2) 500 200 0.4

40** 100(1) + 100(2) 200* Transfer point from GFS** Transfer point to next SA transfer

For next SA transfer…

Successive Addition

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Picture of successive addition test

Successive Addition

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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

Successive Addition

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1E1-S 1E1-S

5E1-S 5E1-S

2E2-S 2E2-S

1E3-S 1E3-S

5E3-S

2E1-S


2E1-S

1E2-S 1E2-S

5E2-S 5E2-S

2E3-S 2E3-S

1E4-S

Side 1 Side 2

100 mg/s (5 Nl/min)Gravimetric point

200 mg/s (10 Nl/min)Gravimetric point

10 g/s (500 Nl/min) 20 g/s (1000 Nl/min)

Successive Addition

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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.

Successive Addition

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

Successive Addition

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Uncertainties

1E2-S (1) (% rdg) 1E2-S (2) (% rdg)Ref Uncert 0.0389 Ref Uncert 0.0389Press 0.0030 Press 0.0030Temp 0.0075 Temp 0.0075StdDev 0.0009 StdDev 0.0015Final Uncertainty Final Uncertainty

0.0397 0.0397

Successive Addition

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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.

Successive Addition

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Flow Traceability

LFE Calibration Chain

Sonic Nozzle Calibration Chain

5 10SLM

0.0010.01

5000

direct gravimetric

successive addition

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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

Verification of Traceability and Uncertainty

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Comparisons – 2ea 1E2 LFE’s at 2 mg/s (100 Ncc min-1)

Date Tested GFS Static(% of rdg) (% of rdg)

28-Oct-05 0.095 ---------5-Jan-06 --------- 0.07

31-Oct-05 0.077 ---------18-Jan-06 --------- 0.07


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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


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Calchain agreement between 1E3-S and 5E3-S compared to 2E3-S in Nitrogen and Air Nitrogen Air slm % Rdg Diff. slm % Rdg Diff.

1E3 vs 2E3 144.9381 0.032 1E3 vs 2E3 145.2471 -0.008 1E3 vs 2E3 194.5104 0.048 1E3 vs 2E3 196.3043 0.001 5E3 vs 2E3 297.1305 0.038 1E3 vs 2E3 251.5949 0.010 5E3 vs 2E3 390.7769 0.017 5E3 vs 2E3 301.6717 -0.081

5E3 vs 2E3 501.6168 -0.095

Calchain agreement between 2E3-S and 1E4-S compared to 5E3-S in Nitrogen and Air Nitrogen Air slm % Rdg Diff. slm % Rdg Diff.

2E3 vs 5E3 370.3781 0.004 2E3 vs 5E3 367.0643 0.022 2E3 vs 5E3 504.4662 0.041 2E3 vs 5E3 501.7000 0.086 1E4 vs 5E3 767.1510 -0.042 1E4 vs 5E3 507.8405 0.013 1E4 vs 5E3 1004.858 0.005 1E4 vs 5E3 1006.8670 0.038


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• 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”

Conclusion

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• 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

Conclusion

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Thank you …

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