Electrical Techniques
Time Domain Induced Polarisation (TD-IP)
Outline
Time domain IP surveys involve measurement of the magnitude of the polarisation voltage (Vp) that results from the injection of pulsed current into the ground. Polarisation voltages primarily result from electrochemical action (ionic exchange) within the pores and pore fluids of the material being energised. The current is applied in the form of a square waveform, with the polarisation voltage being measured over a series of time intervals after each current cut-off using non-polarising electrodes. The measured value of Vp is divided by the steady voltage (observed whilst the current is on) to give the apparent chargeability of the ground. This provides qualitative information on the subsurface geology. TD-IP is primarily used in mineral exploration surveys.
