The invention belongs to electronic technology, is applied to the technical field of
aviation electronics, and particularly relates to a frequency
signal acquisition circuit with an adaptive threshold. The acquisition circuit comprises a clamping circuit, a filtering circuit, a comparison circuit, a threshold generation circuit and a digital shaping circuit, one
branch of an inputted engine rotating speed
signal of an input is insulated and clamped and then connected to a negative input end of the comparison circuit, the other
branch is connected on the threshold generation circuit, and an output of the threshold generation circuit is connected at a positive input end of the comparison circuit. The acquisition circuit has the advantages that an acquisition circuit of a traditional engine rotating speed
signal acquires, restrains and interferes signals through a
hysteresis comparator, and the acquisition circuit solves the problems of fixed threshold of the acquisition circuit of the traditional engine rotating speed signal and poor
interference resistance. The acquisition circuit can automatically change a comparison threshold of the
hysteresis comparator according to change of an amplitude of the engine rotating speed signal of the input, and the
interference resistance of an interface circuit is improved.