The principle and structure of pH meters
The pH value was first measured using a potentiometer to measure electrode potential, which is a zero indicating instrument that balances unknown potentials with accurately known standard potentials. Due to the sensitivity limitation of potentiometers, ordinary potentiometers are not suitable for potential measurement with thin film systems, and this type of pH measurement is very inconvenient to use. In the 1960s and 1970s, with the development of semiconductor technology, transistors gradually replaced electronic tubes in many electronic technology applications, greatly reducing the size and power consumption of electronic instruments. However, due to the fact that transistors are current control devices, their input impedance is much lower than that of electronic tubes. Therefore, it was only after the emergence of varactor diodes that a full transistor pH potentiometer was developed. In the mid to late 1970s, intelligent pH detectors with microprocessors as the core emerged. Implement the calculation and processing of electrode signals and temperature compensation of pH values using software, and characterize the pH value to overcome the unique nonlinearity of pH measurement. The accuracy of instrument detection has been greatly improved, and the functions are more diverse, which can adapt to a wider temperature range. Currently, almost all industrial pH meters are intelligent. The intelligent pH value detection instrument is based on a microcontroller and uses a large-scale integrated circuit chip to process electrode signals and temperature signals. The processed signals are sent to the microcontroller for calculation and processing. The pH value detection instrument is developed based on the formula of equation 3, and its schematic diagram is shown in Figure 1. Due to the use of microcontrollers as the core, complex calculations can be performed, data processing is very convenient, detection accuracy is greatly improved, instrument volume is smaller, and performance is more reliable.
