Device and method for measuring rotational speed of engine based on differential pressure signals of exhaust back pressure

The invention discloses a device and a method for measuring rotational speed of an engine based on differential pressure signals of exhaust back pressure. The device provided by the invention comprises a DPF particle collector, exhaust back pressure difference transducers, a signal transmission cable and a controller, wherein the exhaust back pressure difference transducers are arranged at the front end and the rear end of the particle collector and connected with the controller through the signal transmission cable; and a signal conditioning unit, a signal processing unit, a signal analysis unit and a communication unit are sequentially connected and arranged in the controller. The method provided by the invention includes the steps that pressure difference signals are isolated, filtered and amplified through the signal conditioning unit in the controller; then signal voltage is adjusted to the input range allowable for digital processing, and the digital to analog conversion is performed for sample data; Fourier transform (FFT) is performed for the signals, subjected to conversion, through a digital processing unit, and the impulse frequency is converted into the rotational speed value of the engine taking the revolution/minute (RPM) as the unit through the arranged engine stroke and the amount of cylinders; and finally, the rotational speed is output and displayed through the communication unit in the manner of UART or CAN. The device provided by the invention is not directly contacted with the rotating shaft of the engine, has simple structural form and reasonable design, and is convenient to install and debug.