Experiences with Novel Secondary Conductivity Sensors within the ...

TECHNICAL PAPERS
H
Reference position (Pt 25)
during the determination of
spatial inhomogenity
tions one after another. A spatial inhomogeneity
of 2 mK was determined. Furthermore
a time stability of the
thermostatic bath of 3 mK was found.
An additional temperature control is
given by two calibrated liquid-in-glass
thermometers with a resolution of
0.01 K. The thermometers are positioned
in direct near of the standard measuring
cells (see Fig. 7).
2.5 Metrological Traceability/
Validation of the Calibration
Procedure
The standard measuring cells are traceable
to the primary measuring cells of the
National Institute of Standards and Technology
(NIST), the Physikalisch-Technische
Bundesanstalt (PTB) or the Danish
Institute of Fundamental Metrology
(DFM) by certified reference solutions as
transfer standards. In the frame of validation,
extensive national and international
comparisons were carried out. The
recognition in national and international
comparisons is the highest level of validation
of the developed metrological procedure
and is an important condition for
an international offering of reference
solutions of electrolytic conductivity as
high-quality products.
3. Conclusions
Finally it is possible to say that the conception/creation
of different standard
measuring cells with accommodation to
W
1 2 3 1 2 3
D
Figure 7. Positions of the temperature sensors for the determination of spatial inhomogeneity (H, W, D are dimensions height, width and
depth of the used volume).
H
defined measuring ranges is a new
variant of the metrological trace-ability
of electrolytic conductivity. The aim of
this work is to supply reference solutions
to users in the range from 2 µS/cm to >
100 mS/cm, thereby providing users
metrological traceability to the national
level.” The standard measuring cells represent
the level of reference standard in
the metrological hierarchy of the procedure.
With it the calibration of reference
solutions of electrolytic conductivity is
possible without a break in the given
measuring range. With this development
for the industry/laboratories, there is a
new possibility to purchase reference
solutions for the monitoring of the
processes and to save the accuracy of the
measuring results.
4. Acknowledgments
We thank the Landesförderinstitut
Sachsen-Anhalt (Germany) for the financial
support of the development project.
The authors would like to acknowledge
Dr. Reinhard Lange and Mr. Frank Seifert
from Sensortechnik Meinsberg GmbH
for their suggestions for the development
of the standard measuring cells.
5. References
[1] P. Spitzer and U. Sudmeier, “Electrolytic
conductivity – a new subject field at
PTB,” PTB-report PTB-ThEx-15, PTB,
Braunschweig, pp. 37–47, 2000.
[2] K.W. Pratt, W.F. Koch, Y.C. Wu, and
Position of the electrodes
(cell C and D)
during a measurement
P.A. Berezansky, “Molality-based
[3]
primary standards of electrolytic conductivity,”
Pure App. Chem., vol. 73, no.
11, pp. 1783–1793, 2001.
R.H. Shreiner and K.W. Pratt, “Standard
reference materials: Primary standards
and standard reference materials for
electrolytic conductivity,” NIST Special
Publication 260–142, 2004.
[4] Y.C. Wu, W.F. Koch, and K.W. Pratt,
“Proposed new electrolytic conductivity
primary standards for KCl solutions,” J.
Res. Natl. Stand. Technol., vol 96, pp.
191–201, 1991.
[5] H.D. Jensen and J. Sørensen, “Electrolytic
conductivity at DFM – results
and experiences,” PTB-Bericht PTB-
ThEx-15, Braunschweig, pp. 3–8, 2000.
[6] H.D. Jensen and C. Verdier, “Towards an
improved primary standard for electrolytic
conductivity,” presentation of the
Danish Institute of Fundamental Metrology
at the NCSLI Workshop and Symposium,
2001.
[7] H.D. Jensen and N.-E. Dam, “DFM
measurement capability: Electrolytic
conductivity,” DFM-report DFM-04-
[8]
R81, Lyngby, pp. 1–7, January 2005.
K. Rommel, “Leitfähigkeitsmessungen in
Elektrolyten – Die Wahl der richtigen Frequenz,”
off print from the Fachzeitschrift
für Labortechnik, vol. 12, 1981.
[9] “Guide to the Expression of Uncertainty
in Measurement (GUM),” ISO/IEC
Guide 98, International Organization for
Standardization, Geneva, 1995.
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D