Collocated Electric and Magnetic Field Sensor and Amplifier Design for Non-Invasive Food Scanning System

This paper presents the design of an array of electromagnetic field detectors for a novel food scanning system to detect foreign objects in processing pipes. Each electromagnetic field detector consists of one magnetic field and one electric field sensor. A 10 kHz excitation is applied along a length of pipe, causing a current to flow with an associated magnetic field that is detected by a search coil. The electric field sensor detects changes in the surface potential of the food by amplifying the displacement current from the food surface onto an electrode. Sudden changes in the surface potential and current density are indicative of changes in the local food impedance. The possibility of combining the two sensors to form one collocated sensor was found to be impractical due to opamp limitations.