1 Introduction
Pulse meter is a kind of electronic electricity meter which is more common on the user side of power system. For remote electronic meter reading systems, reliable and accurate metering of the pulse output pulses is required. In this paper, we study the reliable pulse capture and pulse measurement of pulse table, especially the key problems such as wire break alarm and power failure data storage of pulse meter output line, and study the field bus required for regional pulse table group meter reading. A modular solution for pulsed meter clusters using CAN bus for data communication is proposed.
2, pulse acquisition module design
The main task of CH1 pulse acquisition is to calculate the real-time and accurate count of CH2 CH3 pulse meter output pulse. CH4 is the basis of all electricity statistics. The quality of the pulse acquisition module CH5 directly affects the reliability of the whole system and the accuracy of CH6, so it occupies an important position in CH7 throughout the meter reading system.
2.1 The structure of the pulse acquisition board
The specific structure of the acquisition board is shown in Figure 1. Mainly with the single-chip P87C591 as the core, the data acquisition is designed for the 8-channel electric meter, and the data can be stored in the SEEROM, and the module with power-down protection and communication interface is also provided.
The acquisition module is equipped with power-off monitoring and data protection functions. When the power-down condition is detected, data backup is performed in time before power-down to prevent data loss caused by sudden power failure.
2.2 hardware design of pulse acquisition module
According to the design requirements of the system, each acquisition module completes the collection task of 8 electric meters, and needs to occupy 8 I/O interfaces of the single chip microcomputer. A single optically isolated pulse data acquisition circuit is shown in Figure 2.
In the figure, D0 is a VCC protection diode, and R0 is a current limiting resistor to protect the light-emitting diodes in the optocoupler. C10 and R10 form an RC low-pass filter, and D10 is a clamp diode that handles spike-like interference signals. R4 and R5 are voltage dividing resistors. R3 is a pull-up resistor that acts as a current limiter.
The pulse signal output from the meter is 5V DC. After filtering, enter the optocoupler, and then the resistor divides the voltage signal to 4V into the microcontroller. The pulse signal is collected by the P2 port of the single-chip microcomputer P87C591. It can also be seen in Fig. 2 that since the pull-up resistor is connected, the output pulse waveform of the optocoupler is exactly opposite to the output pulse waveform of the meter.
2.3 Software design of pulse acquisition module
The software design of pulse acquisition mainly deals with the accurate sampling of pulses, and performs cumulative processing on the data of the current time period. And the software design includes anti-interference design for repeated detection and anti-jitter. The software flow chart is shown in Figure 3.
2.4 pulse acquisition anti-interference measures
The anti-interference ability of the pulse acquisition circuit determines the accuracy of the system and the reliability of the collected data, and it is necessary to improve the anti-interference ability of the system from various aspects.
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