Experimental setup of three-dimensional volume measurement experiments. Frame A shows a CSF-filled three-dimensional cavity molded into agarose gel with conductivity properties similar to the brain. B shows the conceptual circuit diagram and the control scheme for controlling the volume of fluid contained within the cavity. The reading was sent to a Flow Controller, FC, which controlled a micro pump. Feedback control was implemented using an on-off algorithm and a Flow Transmitter, FT.