Analysis And Applied Design Of Intelligent Multimeter Chip

Intelligent multimeter is a kind of high-quality digital meter with microprocessor or microcontroller, which is a new-type instrument of hardware and software integration, and software determining the level of the smart meter equipment. Its main advantage is high accuracy, strong functions, with automatic calibration, automatic measurement, and automatic data processing capabilities. It is available through RS-232 or IEEE-488 standard interface connected with a computer to complete automatic testing and real-time control. It can be used in the field or laboratory, and can also be embedded in measurement and control system.Study object of this topic is the special multimeter chip FS9704, whose internal core component is a high-resolutionΣ-△ADC that completes measurement functions with other function networks. Meanwhile, FS9704 has the microprocessor interface, and can connect with the microprocessor through interface bus to control FS9704 action.This system is mainly composed of measurement module, microcontroller module, memory module, display module, communication module, and power module. Mixed-signal microcontroller, C8051F020, is as the control unit to achieve control of the measurement module, read-write memory modules, display of display module, communication with PC and other functions. Main research work of this paper is outlined an following:On the one hand, the FS9704 chip's internal structure is studied, and its working principle is analyzed from basic composition and the general working principle of intelligent digital multimeterFirstly, the structure and working principle of FS9704's internal ADC are illuminated, and d its transmission characteristics are discussed, and the conversion algorithm of the ADC output voltage equivalent value is also introduced here.Secondly, FS9704's internal function network is analyzed, and the working principles of functional decoder, multiplexer and pre-filters, operational amplifiers and comparators and some other components are indicated. This part focuses on the function network diagram under mV voltage mode of FS9704.Then, FS9704's microprocessor interface is introduced, and read and write methods of its internal control register are indicated, and its interrupt mechanism and the functions of its measurement registers were studied.Finally, the working principle of FS9704's power system is analyzed.On the other hand, the design ideas and implement methods of each functional module in multimeter chip application system are mainly explained.First, the application system is divided into five function modules: the measurement module, microcontroller module, memory module, display module, communication module and power module.Then, the design and implementation methods of each module are introduced, focusing on core technical issues. Measurement module mainly completes the signal under test conditioning and analog-digital conversion, which is controlled by the microprocessor. Microprocessor via the control interface, according to some control timing sequence achieves control over FS9704. It is available reading some configuration information required by control process from external FLASH memory through SPI interface and writing data records in the memory. The measured results can be displayed on liquid crystal display module. In addition, using communication module, the PC can easily communicate with the microcontroller to monitor the measurement process, storage and display measurement data.In the last place, all functional modules are integrated, and the system function is perfected. Furthermore, a comprehensive test is complete and the results show that the application system can measure DC millivolts, and the measurement accuracy meets to the relevant national standards.