Intelligent instrumentation plays a crucial role in industrial applications, with its measurement accuracy and reliability directly influencing operational efficiency. This article presents the integration of the HART communication protocol to enhance data transmission within smart instruments, focusing on internal structure and process control optimization. A HART smart instrument multiplexer system is established, utilizing an analog PID control algorithm for data regulation and optimal control techniques for automatic parameter adjustment. Additionally, the three-parameter Weibull distribution is employed to assess the reliability of smart meters, deriving distribution characteristics and estimating parameters through failure rate analysis. The performance of the designed HART smart meter multiplexer system is thoroughly evaluated, including control performance, reliability, channel function, and measurement accuracy. Notably, the system demonstrates a minimal overshoot in analog PID control at 0.911%, with a steady-state error range of -5°C to 4°C. Furthermore, the implementation of this system significantly reduces the risk of hazardous failures by 41.91%. In conditions of 350°C temperature and 1.2MPa pressure, the system accurately measures superheated steam flow with a relative error of only 0.05%. By optimizing the settings of smart instruments, this system not only enhances measurement accuracy in industrial production but also improves reliability, supporting diverse applications in the chemical industry.