Design And Development Of Multi-Channel Intelligent Instrument

With the development of control and microcomputer technology, intelligent instruments have been widely used in industrial automation, and play a more and more important role in this area. In recant years, there is an increasing demand for design of intelligent instruments with higher performance.In this paper, with a brief reviewing of the characteristics of intelligent instruments and the relating design methods, a project of developing a multi-channel intelligent instrument is proposed, to meet the demand in industrial applications. The system structure, function and performance index of the multi-channel intelligent instrument are determined.This instrument is based on a micro-controller unit (MCU), P89C664, produced by Philips, with the supporting periphery such as 8Mbits flash memory, 320×240 LCD graphic displayer and real time clock. It can adapt thermocouples, thermo-resistors, standard voltage or current signals via eight analog channels. The MCU processes data acquired by 16-bit ADC, and accomplishes the paperless recorder functions, such as signal monitoring, recording, curve or bar displaying and over threshold alarming. The instrument can output control signals based on various control methods with the help of expanding bus, and communicate with other systems via RS232 or RS485 communication interface.The modularization and structural strategy are adopted in the instrument software programming. The functional driver modules, such as data acquirement, measuring signal processing, data access, key operation, Chinese-character/curve/bar display and so on, are developed associated with the instrument hardware. So far, the instrument has been equipped as a design platform to accelerate development process in the future. Furthermore, a meter reading system based on personal digital assistant (PDA), which can not only copy recorded data, but also accomplish monitoring operations like upper industrial PC, is developed under Windows CE environment. Finally, a conclusion of this paper and some suggestions on further development are presented.