1. First, the signal is conditioned and shaped, and the amplitude is reduced to 5V peak-to-peak through proportional amplification. After 2.5V adder, it is compared with 2.5V reference voltage (voltage comparator) to form a square wave, and then the signal is shaped by two inverters to make the waveform more ideal.

2. Use the counter 74HC 16 1 pair 16 for modulo counting, and send the output value to the single-chip counter (C/T, external counting mode).

3. The sum of the external values of the counter read from the internal count value of the single chip microcomputer * 16+ is the frequency.

4. The signal frequency should be estimated in advance. If the frequency span is large, two channels, high frequency and low frequency, should be set. The low-frequency channel is calculated by periodic measurement method, and the high-frequency channel needs two or more stages of analog-to-digital 16 conversion when necessary, and then it is sent to the single chip microcomputer. Generally, 5 1 single chip microcomputer can easily measure the frequency range of 0. 1Hz- 10MHz.

The most troublesome thing is that the amplitude range of the waveform is very large, such as 10V to 10V, which is a headache.