experiences with novel developed secondary conductivity sensors … · experiences with novel...
TRANSCRIPT
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Experiences with novel developedsecondary conductivity sensors within the
German Calibration Service (DKD)
Ulrich Breuel Ulrich Breuel 11, Barbara Werner , Barbara Werner 22, Petra Spitzer , Petra Spitzer 33, Hans D. Jensen , Hans D. Jensen 44
1,21,2 Zentrum für Messen und Kalibrieren -ANALYTIK- GmbH, D-06766 Wolfen, Germany Zentrum für Messen und Kalibrieren -ANALYTIK- GmbH, D-06766 Wolfen, Germany
33 Physikalisch-Technische Bundesanstalt, D-38116 Braunschweig, Germany Physikalisch-Technische Bundesanstalt, D-38116 Braunschweig, Germany
44 Danish Institute of Fundamental Metrology, DK-2800 Kgs. Lyngby, Denmark Danish Institute of Fundamental Metrology, DK-2800 Kgs. Lyngby, Denmark
230th PTB Seminar Conductivity and salinity - Leitfähigkeit und Salinität PTB Braunschweig, September 13/14 2007
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Agenda Introduction Introduction Measurement quantity Electrolytic ConductivityMeasurement quantity Electrolytic Conductivity Metrological hierarchy for Electrolytic ConductivityMetrological hierarchy for Electrolytic Conductivity NewNew ZMK development in detail ZMK development in detail Measurement of conductance Measurement of conductance GG Determination of the cell constantDetermination of the cell constant The measuring systemThe measuring system Temperature measurementTemperature measurement Cause and effect diagramCause and effect diagram Validation by means of intercomparisonsValidation by means of intercomparisons Summary and acknowledgementsSummary and acknowledgements
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The ZMK group with the calibration laboratory -K-06901
Greatest number of quantities within a calibration laboratory
ZMK -ANALYTIK-
GmbH
Viscosity
Electrolytic conductivity
pH
Liquid density
Volume (Pipettes )
Electricity
Pressure
Mass
Balances
Torque
Time/frequency *
Temperature
Length equipment
Gauge blocks
Humidity
ZMK GmbH Sachsen-Anhalt
Ortsteil WolfenP-D ChemiePark Bitterfeld-WolfenAreal A; Filmstr. 7D-06766 Bitterfeld-WolfenGermany
Phone: +49 (3494) 6973 0Fax: +49 (3494) 6973 34E-Mail: [email protected]* Not accredited yet
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The German Calibration Service (DKD)
Source: www.dkd.eu
Deutscher Kalibrierdienst
The DKD comprises calibration laboratories in industrial enterprises, research institutes, technical authorities, inspection and testing institutes. They are accredited and supervised by the Accreditation Body of the DKD and calibrate measuring instruments and material measures in the range and scope of accreditation.
Location of the ZMK Group
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Quantity electrolytic conductivitywithin the NMI´s
Principle: Measurement of resistances in two different positions realized byPrinciple: Measurement of resistances in two different positions realized by
micropositioner systemmicropositioner system changing of center sectionschanging of center sections
Source: Primary methods for the measurement of electrolytic conductivity;
Accred. Qual. Assur (2003) 8:346-353
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Quantity electrolytic conductivitywithin the DKD
Typical situation in the DKDTypical situation in the DKD
Measurement with commercial instruments and devices using 2- and 4-pole Measurement with commercial instruments and devices using 2- and 4-pole cells (same level as the users in the industry)cells (same level as the users in the industry)
Disadvantages:Disadvantages: Non-linearityNon-linearity Temperature compensationTemperature compensation Measuring uncertainties are too highMeasuring uncertainties are too high Dependence from the manufacturersDependence from the manufacturers
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New standard cells by ZMK
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Metrological hierarchy for electrolytic conductivity
Primary cells
Commercial measuring instruments and devices for
electrolytic conductivity
Reference standards (Standard cells)
Transfer standards:Certified reference solutionsfor electrolytic conductivity
Calibration objects
(of the nationalmetrological institutes )
Realized in the DKD by the results of the development project
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New ZMK development in detail
Temperature independenceTemperature independence
Direct traceability to primary cellsDirect traceability to primary cells
Low measuring uncertaintiesLow measuring uncertainties
Manufacturer independenceManufacturer independence
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New standard cell
Schematic image of a standard cell
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Several types of cells needed?!
1.3 µS/cm 15 µS/cm 100 µS/cm 1 mS/cm 20 mS/cm
Deinionized water(appr. 1 µS/cm)
Rainwater(50 µS/cm)
Drinking water(500 µS/cm)
Industrial wastewater(5 mS/cm)
Seawater(50 mS/cm)
5 µS/cm …lowest value with
available reference solution in the DKD before finishing the
development project
Source of conductivity values: Principles of measuring technique, WTW GmbH
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Extended measuring rangeby several cells
Cell A Cell B Cell E Cell C Cell D
4 mm
Platinization
Measuring Range
1.3 µS/cm 15 µS/cm 100 µS/cm 1 mS/cm 20 mS/cm
6 mm 20 mm 60 mm 60 mm
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Standard cells
5 standard cells for different ranges of 5 standard cells for different ranges of electrolytic conductivity available (identified electrolytic conductivity available (identified with letters A to E)with letters A to E)
4 mm 60 mm
A D
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Measurement of conductance G
BjGY ⋅+=
Real part … needed for determination of electrolytic conductivity
Conductance G in S
Imaginary part … not used
Susceptance B in S
Complex conductance Y in S
(1)
RG /1= (2)Ohmic resistance R in Ω
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Example of G at different frequencies
Frequency range 0.5 to 5 kHz
y = -46.89x + 5.8656R2 = 0.9999
5,76
5,77
5,78
5,79
5,80
5,81
5,82
5,83
5,84
5,85
5,86
5,87
0,0000 0,0005 0,0010 0,0015 0,0020 0,0025
1/f in KHz-1
G in
mS
The conductance as a function of the reciprocal frequency
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Determination of the cell constant
Frequency range 20 to 200 Hz
y = -1.7862x + 28.673R2 = 0.9976
28,57
28,58
28,59
28,60
28,61
28,62
28,63
28,64
28,65
28,66
28,67
0,0000 0,0100 0,0200 0,0300 0,0400 0,0500 0,0600
1/f in KHz-1
G in
µS
Example: determination of the cell constant of cell B
K = 0,1743 cm-1
Reference solution 5 µS/cm (nominal value), Hamilton Bonaduz AG, lot no. WO 12222520, certified by DFM (C0316)
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Complete set-up for electrolytic conductivity determination
5 standard measuring cells5 standard measuring cells LCR-meter (Agilent 4284A)LCR-meter (Agilent 4284A) Precision thermostatic bath (oil bath, Precision thermostatic bath (oil bath,
Lauda Proline PV 36)Lauda Proline PV 36) Temperature measuring device Temperature measuring device
(temperature sensor Pt25 and (temperature sensor Pt25 and temperature indication instrument TTI-2)temperature indication instrument TTI-2)
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Temperature measurement
Measuring electrodes of cell C and cell D
Spatial inhomogenity:
2 mK
Time stability:
3 mK
Temperature sensor:
Calibrated at temperature fixed points
Positions of the temperature sensors for the determination of spatial inhomogenity
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Cause and effect diagram
Electrolytic conductivity
Cell constant
CO2 influence
CO2 Suppression factor
Conductance (LCR-Meter)
Drift of the reference cell
Bath homogenity
Conductivity reference cell
CO2 Equilibrium
CO2 Sensitivity coefficient
Temperature device
LCR-Meter
Conductance (LCR-Meter)
Extrapolation
Temperature coefficient
Temperature device
Temperature coefficient
Thermometer
Bath stability
Extrapolation
Repeatability
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Validation by means of intercomparisons
2006
2005
2007
Intercomparison on electrolytic conductivity 2005 (5 µS/cm)
EUROMET Electrochemical Analysis WG Project 918; Study on the traceability of salinity measurements in seawater
Intercomparison on electrolytic conductivity 2007 (5 µS/cm)
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Summary
Development of several standard cells Development of several standard cells with accommodation to defined with accommodation to defined measuring ranges is an improvement of measuring ranges is an improvement of the metrological traceability of electrolytic the metrological traceability of electrolytic conductivityconductivity
The aim – supply of reference solutions The aim – supply of reference solutions in the range from in the range from 1.3 µS/cm to > 100 1.3 µS/cm to > 100 mS/cmmS/cm is solved; national is solved; national
NewNew metrological metrological procedure is validatedprocedure is validated and active applied by ZMKand active applied by ZMK
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Acknowledgements
We thank theWe thank theLandesförderinstitut Sachsen-AnhaltLandesförderinstitut Sachsen-Anhalt (Germany) (Germany)
for the financial support of the development for the financial support of the development project.project.
The authors would like to acknowledgeThe authors would like to acknowledgeDr. Reinhard LangeDr. Reinhard Lange and Mr. and Mr. Frank SeifertFrank Seifert
from Sensortechnik Meinsberg GmbH for their from Sensortechnik Meinsberg GmbH for their suggestions for the development of thesuggestions for the development of the
standard measuring cells.standard measuring cells.
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Thank you for Thank you for your attention !your attention !
ZMK GmbH Sachsen-AnhaltZMK -ANALYTIK- GmbH
http:// www.zmk-wolfen.de
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References
Guide to the Expression of Uncertainty in Measurement (GUM), 1st edition 1993,revision and restrike print 1995, International Organization for Standardization, Genf
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K. Rommel, Leitfähigkeitsmessungen in Elektrolyten – Die Wahl der richtigen Frequenz, off print from the Fachzeitschrift für Labortechnik vol. 12, 1981
8
H.D. Jensen, N.-E. Dam, DFM measurement capability: Electrolytic conductivity – January 2005, DFM-report DFM-04-R81, Lyngby, 2005, pp. 1-7
7
H.D. Jensen, C. Verdier, Towards an improved primary standard for electrolytic conductivity, presentation of the Danish Institute of Fundamental Metrology at the NCSLI conference 2001
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H.D. Jensen, J. Sørensen, Electrolytic conductivity at DFM – results and experiencesPTB-Bericht PTB-ThEx-15, Braunschweig, 2000, pp. 3-8
5
Y.C. Wu, W.F. Koch, K.W. Pratt, Proposed new electrolytic conductivity primary standards for KCl solutions, J. Res. Natl. Stand. Technol., vol 96, pp. 191-201, 1991
4
R.H. Shreiner, R.H., K.W. Pratt, Standard reference materials: Primary standards and standard reference materials for electrolytic conductivity, National Institute of Standards and Technology Special Publication, 2004, pp. 260-142
3
K.W. Pratt, W.F. Koch, Y.C. Wu, P.A. Berezansky, Molality-based primary standards of electrolytic conductivity, Pure App. Chem., vol. 73, no. 11, pp. 1783-1793, 2001
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P. Spitzer, U. Sudmeier, U., Electrolytic conductivity – a new subject field at PTBPTB-report PTB-ThEx-15, PTB, Braunschweig, 2000, pp. 37-47
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