Development of Lock-in Resistivimeter for Measuring Resistivity and Induced Polarization under High Electrical Noise

The Cole-Cole RC circuit and the reduced clay models were tested with 3 levels of white noise in order to test a low cost lock-in resistivimeter. The device has maximum power of 60W and showed reliable stability under 67% and 11% of white noise in the previous models. The equipment was made with low cost components and yet can provide a frequency sweep from 13 to 120Hz to the transmitter which allows better signal sampling. The viability of this frequency bandwidth for application in Spectral Induced Polarization (SIP) were also studied. This model was used to find the less time consuming operational settings able to recover the Cole-Cole exponent and relaxation time, in other words, which are the minimum number of frequency samples that is necessary to reconstruct the Cole-Cole curve. An inversion scheme based on the partial sweep of the solution space was implemented. We found that 16 frequency samples are enough to recover the relaxation time with variations below one order of magnitude. Therefore, the results showed good performance for ours resistivimeter. The suggested applications is not only restricted to field measurements but also to lab samples studies related to SIP, resistivity and IP under high electrical noise.