Electrodes for resistivity tomography in coal mines

摘要

Electrodes forming an array for coal-seam resistivity tomography are constructed from conductive plastic rods 45 and conductive resin 46 so that they can remain in place in the coal seam 41 during the mining operation, whereupon the mined fragments are separated from the coal during the washing process. The electrodes may utilise a conductive disc 43 and compressible conductive foam 42 held in place on the rib-side wall, and may utilise alternating electric current to aid the coupling of the signal. The electrodes may be formed by an adaptation of the rib bolts that are commonly used to stabilise the rib-side walls. A resistivity tomography array utilising such electrodes, together with an electrical bus and a system of addressable switches, utilises control signals that are modulated onto the current-drive or voltage-sense bus wires such as to avoid the need for additional control wires in the bus.