The Design Of Pressure Transmitter Based On C8051F Single Chip

Liquid level apparatus is an important instrument for factories to realize automatic production. Its main purpose is for detection and control of liquid level of various containers. As the electronics develops as well as the demand for automatic production and energy saving and emission reduction grows rapidly, the relevant enterprises'need for liquid level apparatus increases sharply. Meanwhile, the requirement for intelligence of liquid level apparatus improves gradually. Such as the requirement for intelligent multifunction, high-accuracy, low power consumption and bus communication etc.It is a rapidly grown technology to make use of microwave to detect liquid level. This instrument is called radar level meter. For being free of restrictions from bad detective conditions such as high-pressure, high-temperature, high humidity and high volatility, the accuracy of product can reach to 1%. It also has a wide adaptability which can works in variety of real industrial environment. But traditional liquid level apparatus does not be built with the function of measuring the liquid pressure. For many users, the practical need for measuring media pressure exists, especially for the conditions in high–pressure oil container.This paper comes from the project of designing a multifunction radar liquid level apparatus. It makes a research in designing a kind of liquid pressure transmitter of low cost, low power consumption, functioning to transmit analog voltage signal captured from the pressure sensor to digital signal and display it via segment type LCD, meanwhile, the pressure data will be transmitted to communication bus by MODBUS protocol. This paper makes deep research in the theory of expatiating the method and process to develop the hardware and firmware of a practical pressure transmitter.This paper includes five parts. The first part is introduction, describing the history, current situation and the classes of pressure transmitter, narrating in short the meaning and process of this system. In the second part the MODBUS protocol is introduced in brief. The third part is the principal of the system and the hardware design. It mainly introduces the application of C8051F serial single chip, the classification of pressure sensors and characteristics, the design of power circuit, signal conditioning circuit, LCD driver circuit, RS-485 communication circuit. The fourth part is firmware, including the main function, signal-capturing sub program, key scanning sub program, LCD driver sub program, MODBUS driver sub program. The fifth part is summary and long-range perspective.