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A seed-counting system was put forward with a cantilever beam detecting the impact of falling seeds, a piezoelectric sensor converting the impact into electrical signals, and a micro-controller counting and displaying seed counts. Based on the classical secondorder transfer function model of the spring-mass-dashpot system, the natural frequency and damping ratio were analyzed. By using appropriate polymer material and signal conditioning, a testing system with proper damping ratio was constructed. The impact of a single seed became a single fast decaying pulse signal so that easy counting could be implemented. The experimental system showed the measurement error was less than 04% in single seed counting tests.