Scale Model Studies of a Transient Electromagnetic Prospecting System Using an Interactive Minicomputer
Scale models have been used for over thirty years in studying the electrical and electromagnetic techniques of geophysical prospecting, and are particularly useful when mathematical or numerical methods are unreasonably difficult. A model study facility has been set up at Macquarie University, Sydney, Australia, to study the transient electromagnetic method of geophysical prospecting. The basic unit in the facility consists of a 35Kword INTERDATA minicomputer which controls the timing and waveform of the transmitted pulse as well as subsequent data collection and processing. A wide-band amplifiler provides an interface between the computer and the small multiturn loops used for model studies. Input and output data are fed via the computer to a teletypewriter. The use of an interactive technique between the computer and operator enables optimum timing and amplifier settings to be easily determined for each model. A model of a uniformly conductive half-space was used to validate the experimental arrangement, and excellent agreement was found between theoretical and model results. A model study of an orebody enabled estimates of bulk conductivity to be made.
A high-bandwidth induction sensor coil
A description is given of an induction sensor coil, the main application of which is in low-level transient electromagnetic detection. The coil is a compact air-cored spiral design of high bandwidth with low distributed winding capacitance. The optimum signal-to-noise ratio is determined by the size of the coil and the noise voltage source of the field effect transistor (FET) used in the input preamplifier.
Mt-field of H-polarization in models with dipping interfaces
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