Design of Electrical Conductivity Measuring Device Based on STM32

Plant factory is an important development field of modern facility agriculture. The electrical conductivity can indirectly reflect the concentration of soluble salt and thus reflect the concentration of nutrient solution. Conductivity measurement is widely used to detect moisture or nutrient solution in plant plants. Aiming at the low measurement accuracy caused by concentration polarization in the measurement process of nutrient solution conductivity, a platinum electrode conductivity sensor was selected, and a conductivity measuring device was designed based on the embedded system of STM32F429. The AD9850BRS chip was used to generate sinusoidal wave signal to reduce the concentration polarization effect near the electrode, and AD637 chip was used to collect voltage. ADA4817 was used to filter the clutter of acquired signal. In order to improve the measurement accuracy, the temperature sensor data is used to correct the conductivity measurement value. The data is printed through the serial port and recorded by the SD card, and adjusted and displayed through the LCD touch screen. Finally, the fabrication, welding and calibration of the circuit board are carried out. The results showed that the calibrated electrical conductivity measuring system operated stably with high measurement accuracy, and could meet the requirements of electrical conductivity measurement of plant plant cultivation nutrient solution.