capacitance measuring device

The principle of this project is to measure the thickness of paper based on the characteristics of capacitance at frequency. The signal generator emits a positive wave with a specific frequency and then goes through a stabilizing circuit to stabilize the amplitude of the positive wave signal to ensure signal strength. The positive and negative signals pass through the voltage parallel negative feedback composed of capacitors and then are amplified (A=C reference/C measurement) and input into the filter circuit to filter out the 50HZ power frequency signal interference. Finally, the peak value of the output signal is sent to the microcontroller through the peak detection circuit. After detection by the microcontroller AD, the number of papers is calculated. The circuit is mainly composed of a positive wave generating circuit, a signal detection circuit, a filter circuit, a peak detection circuit, a data processing circuit, and an input and output circuit. The detection circuit principle is based on the capacitive reactance characteristics of the capacitor under the positive signal. The data processing circuit is completed using stm32f0 microcontroller, and the display circuit uses 0.96-inch OLED.