Design of portable equal-precision frequency meter based on STM32

This         design is an equal - precision frequency meter based on S TM32 . It uses a 18650 lithium battery to power the design . It uses S Providing power, the onboard T P4056 charges the battery. The measured signal is transformed into a square wave identifiable by MCU through high-pass filtering, diode limiting, A D827 amplification, and shaping processing. A D flip-flop is used to realize the transformation from the preset gate to the actual gate. The external microcontroller is used in the actual gate. Counting counts the measured signal after shaping, and the internal 7 2MHZ counter counts to simulate counting the standard frequency, using the principle of equal-precision frequency measurement to achieve equal-precision measurement.

        This design completes a digital frequency meter based on the equal-precision frequency measurement method. It realizes the measurement of sine wave, triangle wave and square wave with amplitude Vpp greater than 200mV and frequency range 1HZ-7MHZ. The measurement accuracy of square wave can reach the power of 10-6 in the whole frequency range. The measurement accuracy of triangle wave and sine wave can reach 10-6 when the measured signal is greater than 10Hz. When the measured signal is between 1Hz and 10Hz, the accuracy is 10-4 to the power.