We recently derived a very general representation formula
for the boundary voltage perturbations caused by internal
conductivity inhomogeneities of low volume fraction (
cf. Capdeboscq and Vogelius (2003)). In this paper we show how this
representation formula may be used to obtain very
accurate estimates for the size of the inhomogeneities
in terms of multiple boundary measurements. As demonstrated
by our computational experiments, these estimates are significantly
better than previously known (single measurement) estimates,
even for moderate volume fractions.