Development of instrument detecting nonmetal foreign body in food material

The authors propose a method for detecting nonmetal foreign bodies mixed in minced fish. The phase of the reflected waves from minced fish containing and not containing a few kinds of nonmetal foreign bodies were measured by setting the minced fish between two electrodes with high frequency voltages. The results showed that the optimal frequency of the voltage supplied to the electrodes was 10 MHz and the phase detector needs a precision of 0.1 deg. A high-speed phase degree measuring instrument was developed using an adaptive sampling method and DSP. The instrument made it possible to measure the phase every 5 ms with a precision of 0.1 deg. However, the judgment of the foreign bodies was difficult, because the phases value of the minced fish changes in the floating experimental condition. The problem was solved by using a neural network with a backpropagation learning method. The computer simulation results showed that a glass bead, a styrene foam and paper could be detected