Capacitively-Coupled Electrical Resistivity

(C-CER)

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The C-CER or OhmmMapper method measures the electrical resistivity of the subsurface, both laterally and vertically, to infer rock/soil types, stratigraphy, subsurface infrastructure, voids, etc. Typically, grain-size, porosity, rock-type, temperature, ice content and water saturation are the primary factors controlling resistivity.  Clays and silts are conductive (low resistivity) compared to sands and gravels. In addition, resistivity generally increases as soil grain size and interstitial void space increases.

C-CER instrumentation measures ground resistivity without the use of conventional electrodes that are required for traditional galvanic resistivity surveys. Instead, instrumentation consists of an ungrounded transmitter, a receiver array of up to five receivers and a data logger.  An alternating current is coupled to the ground by the transmitter, inducing a current to flow within the ground.  This resulting secondary current couples a current to the receiver array.  The measured voltage is proportional to the apparent resistivity of the ground between the transmitter and receiver array.