The Research Of Multi-Parameter Measurement Instrument For Sewage Disposal System

As a rising technology, the recycle of the sewage resource catches an increasing attention at home and abroad. It can realize the treatment of the residential sewage ecologically and innocuously. In view of parameters measurement demands of sewage treatment plants, the subject developed a multi-parameter measurement instrument used for sewage disposal system. The hardware platform used ARM9 as the kernel unit and added CAN controller, Ethernet cuntroller, LCD screen, keyboard and so on. The parameters needed to measure are Oxidation-Reduction Potential (ORP), Dissolved Oxygen (DO), content of ammonia nitrogen. The Oxidation-Reduction Potential (ORP) measurement adoped depolarized method; the Dissolved Oxygen (DO) measured by Clark dissolved oxygen electrode; and the content of ammonia nitrogen measured by ammonia gas sensing electrode. In order to enhance the precision and reliability of measurement, the measurement instrument designed a second order active filtering circuit to filter the High-Frequency sharp wave in the signals. In the software, median average filtering method is used to suppress electromagnetic interference (EMI); Kalman flitter algorithm is adoped to reduce ammonia gas measurement noise.The instrument is designed to fulfil different needs in different plants. The instrument can achieve the function for get local measured data and display, storage and playback of the data so that it can use as Single Host Model. Becouse of the CAN and Ethernent interface have designed, users can select the appropriate mode to get data by network transmission, so that it can extend long-range supervisory control and optimizing control functions.The software is based on the embedded Linux operating system. The data acquisition and data processing program are developed after porting the bootlorder program, Linux operating system and the YAFFS root file system to the S3C2410 platform. As the interface of application software for accessing the low level hardware, the hard device drivers play important roles in embedded system. The paper introduce the three levels of CAN device driver design witch is insure the CAN bus communication.