Study On Coarse Grating Displacement Measuring System Based On Single Chip Microcomputer And CPLD

For half a century, many countries all over the world have been trying to develop displacement sensors and digital measuring systems. Nowadays, the cost for producing a raster displacement measuring system has been sharply reduced because of the advancing technologies of opto-etch, duplication and microelectronics. The up-to-date grating measuring systems can measure with the accuracies of micron, sub-micron or even nanometer. A variety of raster are applied to up to 90% machine tools and meters for displacement measurement and control. The coarse grating measurement systems employ coarse grating with 0.635mm gape, and a Self-Scanning Photo Diode Array Sensor CG200 receives the light signal. The merit of the coarse grating measuring systems includes large gap between the sensor and the grating, easiness to connect and high reliability.In this paper, a coarse grating displacement measuring system based on single chip microcomputer and CPLD is investigated. CPLD is used to realize phase demodulation and high division, while the single chip microcomputer is applied for data sampling, data process and display etc.The included content is as follows:1. The brief presentation of the basic principal, next the analysis of the measuring speed and measuring accuracy, then the conclusion that high speed and accuracy rely mainly on the performance of the sensor.2. The process of the analogue signal. This part includes filtering, waveform conversion and the amplitude monitoring.3. The programming of the CPLD. Including the driving signal generation for sensors, the realization of both the phase demodulation and the division, and the generation of the controlling signals needed for connection between microchip and its peripherals.4. The hardware design of the system. Including the interface to keyboard and liquid crystal displayer power source monitoring and reset circuits, the extended RAM, the connection to CPLD etc.5. The software design of the system. C language is used here to program for measurement, keyboard, liquid crystal displayer, data safety, etc.6. The design of system PCB board and component mounting.