Monitoring pH Sensor with Temperature Compensation using MCU 32-bit Equipped with RS-485 Communication Module

Abstract

This study discusses the application of an automatic temperature compensation (ATC) system on pH sensors to improve accuracy to 0.01 pH. The analog values (mV) of pH solutions are very low and susceptible to interference and temperature fluctuations, so an independent pH module was developed with a differential sensor, a DC-to-DC isolator module, and an Op-Amp module as a buffer to stabilize the analog signal. The gradient method was used to manage the slope between temperature and pH, and the ATC formula from Hanna Instruments was applied for temperature compensation. Test results show that pH shifts occur every time the solution temperature decreases, and ATC is able to correct pH measurements. However, the target accuracy of 0.01 pH has not been achieved due to differences in calculation results between manual calculations and the microcontroller. The measurement error percentage of the microcontroller is 0.6%, resulting in an accuracy percentage of 99.4%.