Three-dimensional sensitivity distribution and sample volume of low-induction-number electromagnetic-induction instruments

James B. Callegary, Paul A Ferre, R. W. Groom

Research output: Contribution to journalArticle

18 Citations (Scopus)

Abstract

There is an ongoing effort to improve the understanding of the correlation of soil properties with apparent soil electrical conductivity as measured by low-induction-number electromagnetic-induction (LIN FEM) instruments. At a minimum, the dimensions of LIN FEM instruments' sample volume, the spatial distribution of sensitivity within that volume, and implications for surveying and analyses must be clearly defined and discussed. Therefore, a series of numerical simulations was done in which a conductive perturbation was moved systematically through homogeneous soil to elucidate the three-dimensional sample volume of LIN FEM instruments. For a small perturbation with electrical conductivity similar to that of the soil, instrument response is a measure of local sensitivity (LS). Our results indicate that LS depends strongly on the orientation of the instrument's transmitter and receiver coils and includes regions of both positive and negative LS. Integration of the absolute value of LS from highest to lowest was used to contour cumulative sensitivity (CS). The 90% CS contour was used to define the sample volume. For both horizontal and vertical coplanar coil orientations, the longest dimension of the sample volume was at the surface along the main instrument axis with a length of about four times the intercoil spacing (s) with maximum thicknesses of about 1 and 0.3 s, respectively. The imaged distribution of spatial sensitivity within the sample volume is highly complex and should be considered in conjunction with the expected scale of heterogeneity before the use and interpretation of LIN FEM for mapping and profiling.

Original languageEnglish (US)
Pages (from-to)85-91
Number of pages7
JournalSoil Science Society of America Journal
Volume76
Issue number1
DOIs
StatePublished - Jan 2012

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spatial distribution
sampling
electrical conductivity
perturbation
soil
surveying
distribution
soil properties
soil property
spacing
simulation

ASJC Scopus subject areas

  • Soil Science

Cite this

Three-dimensional sensitivity distribution and sample volume of low-induction-number electromagnetic-induction instruments. / Callegary, James B.; Ferre, Paul A; Groom, R. W.

In: Soil Science Society of America Journal, Vol. 76, No. 1, 01.2012, p. 85-91.

Research output: Contribution to journalArticle

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