| With the rapid development of economic and social,the number of water meters, electric meters and gas meters has increased rapidly. The traditional way of reading meter due to the shortcomings of high error of reading meters, difficult to unify the operation and delay times, it has been difficult to meet the needs of social development. The traditional meter reading can not meet the needs of today’s society, the automatic meter reading system has instead of traitional way gradually.Concentrator, the bridge of multi object automatic meter reading system, is the most important of components in the system. The function of the concentrator is collect〠storage and manage the data of intelligent meter. Besides, it must transfer the data to the host and execute the command of it efficiently. At present, the key problem to be solved is how to improve the ability of processing multi object concentrator data, and accomplish upstream and downstream communication efficiently.The Meter-Bus technology is a bus technogy applying to the pulic utilities instruments specially. It has been widely used in the automatic meter reading system. The Meter-Bus is supplied by two wire. In the two lines, it can supply the power and transport the demodulation signal of uplink current and uplink voltage.In the traditional scheme, the pre-stage of uplink current demodulation is composed by the RC analog filter and the reference level. The RC filter’s cut-off frequency of this scenario, on the one hand, has brought about baseline drift because of the temperature drift of the capacitance and resistance. On the other hand,it has brought about a large differences because of the errors of the component values.The above shortcomings lead to to the implementation of each program must re-adjust the reference level, it has brought great inconvenience for the production and construction.In this paper, we proposed a digital demodulation scheme of uplink current for the above mentioned problems. The idea is to use the chip of Cortex-M3(LM3S5749). It has the advantage of low-cost and high reliability. It has realized the digital current demodulation using the chip’s high-speed ADC and digital signal processing, it can solve the above problems effectively, and also embeded the last stage of Meter-Bus current demodulation(composed by operational amplifiers and comparators in the traditional concentrator). It enhanced the ability to adapt the different enviroments, and applied to the concentrator in the automatic meter reading system successfully. |
