Using sensors in agricultural engineering has improved agricultural machines performance and has increased the accuracy, safety and convenience of farm works. One of the complex farm machines is grain harvester and evaluate by measuring grain loss. Piezoelectricity effect refers to a capability some materials enjoy in terms of transforming mechanical energy into electrical energy and vice versa. When subject to an impact, piezoelectric sensors produce a voltage of an amount proportional to the intensity of the impact. Knowing that the corresponding range of voltages to the impacts by wheat grains is different than that of straw, the voltage can be amplified and sent to the processor. In order to measure grain loss incurred by cleaning unit of a combine harvester, five piezoelectric sensors are used at an approximate spacing of 14 cm. TL072 and LM311N were used to amplification of the recorded signal. In order to evaluate the sensor performance, the device was subject to in-lab investigations. The results showed good fitting between the recorded actual data.
