Digital and analog proceeding of signals from grain impact sensors

Abstract Piezoelectric acoustic grain impact sensors were interfaced to an 8-bit microprocessor with the aim of discriminating between grain and non-grain impacts and counting grain impacts. Although impact signals were digitized successfully, the microprocessor was not fast enough to allow discrimination of signals in real time. Analog circuitry was constructed to discriminate between grain and non-grain impacts on the basis of signal amplitude and frequency. This circuitry was used, in conjunction with the microprocessor, in a four-sensor system which, in laboratory tests, gave counts within 10% of true values at impact rates up to 35 kernels per second. This performance was considered to be sufficient to justify further testing of the system in straw walker environments.