We have designed a frequency-domain electromagnetic induction sensor for imaging the distribution of electrical conductivity of soils in civil engineering applications. The device implements the ultimate technical feasibility of measuring harmonic signals on the ground surface. Digital recording and narrow bandpass filtering of synchronous detection allows a sufficient measurement accuracy for ˜1 μV signals and suppression of power-line noise of more than 100 dB. We suggest practical methods for investigating the characteristics of the sensor and estimating its measurement accuracy.
