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| Titel |
Extension of the measurement range of electrical conductivity by time-domain reflectometry (TDR) |
| VerfasserIn |
M. A. Mojid, G. C. L. Wyseure, D. A. Rose |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1027-5606
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| Digitales Dokument |
URL |
| Erschienen |
In: Hydrology and Earth System Sciences ; 1, no. 1 ; Nr. 1, no. 1, S.175-183 |
| Datensatznummer |
250000091
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| Publikation (Nr.) |
 copernicus.org/hess-1-175-1997.pdf |
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| Zusammenfassung |
| The electrical conductivity (EC) of a medium invaded
by TDR sensors can be estimated from the impedance of a TDR reflectogram.
Four categories of sensor were tested in salt solutions and the impedances
of the TDR pulse wave were correlated to the EC of the solution. The relation
between the impedance and EC over a wide range of conductivities is non-linear
but stable. Second- to fourth-degree polynomials can extend the measurement
range to
44 dS m-1 (equivalent to a NaCl concentration
of 28 g l-1 or 0.48 N) and result in better
prediction of the conductivities than linear relations. For automatic measurement
of EC with a datalogger, the method of Giese and Tiemann
(1975, Adv. Mol. Rel. Processes, 7: 45-59) gives accurate measurement of conductivities
lower than 10 dS m-1. Polynomial relations
between EC and the datalogger's record provide an accurate estimate of
the conductivity over a wide range. However, for both manual and automatic
measurements, the sensors need to be calibrated individually. In particular,
in the non-linear region, the differences between sensors are larger. Fortunately,
the relation is sufficiently stable to eliminate significant error. |
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