With the advancement of technology, the way of meter reading has evolved from traditional on-site manual methods to remote automatic systems. Today, several techniques are used for meter reading, such as RS 485 bus, infrared, and power line carrier communication. While these methods are relatively mature, each has its own limitations. For instance, RS 485 requires wiring, which increases costs and restricts transmission distance to under 1,200 meters. Infrared-based meter reading still needs on-site personnel, and power line carrier communication is affected by electromagnetic interference, limiting its effective range. In contrast, GPRS communication technology offers a more flexible and efficient solution. It boasts a wide network coverage, low cost, and the ability to stay online permanently. Its independence from distance and physical space makes it an ideal choice for modern metering systems.
GPRS Network Energy Meter
The GPRS network energy meter integrates GPRS communication technology with traditional metering functions. It combines a three-phase multi-function energy meter with a GPRS communication module, enabling wireless data transmission. This device consists of two main components: the base meter and the GPRS communication module.
1.1 Base Meter
The base meter performs all the standard functions of a conventional three-phase multi-function electric meter. Even without the GPRS module, it can operate independently. It supports real-time sampling and processing of AC analog signals, energy measurement, demand calculation, time-of-use billing, load curve storage, data freezing, event logging, and user prepayment control. It also allows for remote control and local monitoring. The base meter includes interfaces like RS 485, infrared, and GPRS, enabling data retrieval and configuration. It also features a local LCD display for user interaction.
1.2 GPRS Communication Module
The GPRS communication module serves as the key component for transmitting data from the meter to the central system. Designed as a standalone unit, it ensures reliable data transfer without affecting the base meter’s accuracy. The module communicates with the base meter using the DT/L645 protocol and connects to the primary station via the "Power User Information Collection System Communication Protocol" (Q/GDW 376.1-2009). This ensures seamless integration into existing metering infrastructure.
2. GPRS Communication Module Hardware Structure
2.1 System Block Diagram
The GPRS wireless communication module consists of several key components: an ARM microprocessor (LPC2138), a GPRS module, FLASH and ferroelectric memory, an infrared transceiver, RS 232 debugging interface, RS 485 communication port, JTAG simulation interface, LED indicators, and a power conversion unit.
Figure 1: GPRS Network Energy Meter System Block Diagram
2.2 Module Function
2.2.1 Microprocessor
The LPC2138 is a 32-bit ARM7TDMI-S core microcontroller with 512 KB of internal FLASH and 32 KB of RAM. It includes various peripherals such as timers, ADCs, DAC, PWM, GPIOs, interrupts, RTC, and multiple serial interfaces. It also supports ISP/IAP programming, low-power modes, and a PLL for up to 60 MHz operation.
2.2.2 GPRS Module
The M580z module from Shenzhen Youfang Technology is used, featuring a built-in TCP/IP stack, dual communication channels, and a simplified AT command set. It connects to the microcontroller via a TTL-level serial port.
2.2.3 Memory
To store large amounts of data, such as curve data and events, a high-capacity FLASH is used. Ferroelectric memory is employed for real-time data and settings that require frequent updates. The SPI interface connects the memory to the microprocessor.
2.2.4 Serial Interface and JTAG Port
The RS 232 and infrared ports allow local configuration and maintenance. The RS 485 interface enables data access from the master station. The JTAG port is used for debugging and programming the ARM processor.
2.2.5 LED Indication
LEDs indicate the power status, login status, network connectivity, and power-on condition of the module.
2.2.6 Three-Phase Energy Meter
The three-phase energy meter collects and calculates energy, voltage, and current data. It communicates with the microprocessor via a serial port using the DT/L645 protocol. The module periodically reads real-time data like power, demand, voltage, and current, storing it for access by the central system.
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