R/D Of Real-time Subsection Ammeter Based On ATT7022B

This paper around multi-purpose power meter design requirements, from two major aspects—the system hardware design and system software design, stresses the ammeter's real-time subsection detection and measurement,multi-function and network. The purpose is to enable ammeter measure respectively and accurately in both case—ultra-low-load and normal load always, in order to achieve the full range precision balance and accurate measurement. The core and innovation is real-time subsection detection and measurement.In the system-hardware-design, the hardware design to the core—real-time subsection detection and measurement is: When the load current is not more than 20% of rated current, MCU output low level to control simulation-switcher switch to the low-end of current transformer's secondary- change; When the load current is greater than 20% of rated current, MCU output high level to control simulation-switcher switch to the high-end of the current transformer's secondary-change. Then the two cases will be respectively and automatically measure by the measurement-IC and MCU, then storaging and refreshing meter's core datas with memory, then displaying with LCD. The hardware design to multi-function is: With three keys, categorily displaying all kinds of meter's datas; With buzzer, sending alarm of abnormal cases; With memory, storaging and refreshing the data of making meter multi-function; Wih MCU-pin, clearing memory's data; With real-time clock module and back-up batteries, providing real-time clock; With normally-closed switch, connecting and disconnecting backlight of LCD. The hardware design to network is: With communication-IC and convert-interface, transmiting ammeter's data to PC; With memory, providing PC for enquire of all meter's data which has been saved.In the system-software-design, the whole flow chart of ammeter is given firstly, and then respectively broken down the whole flow chart into a number of modules in order to analysis. The software design to the core—real-time subsection detection and measurement is: first read apparent power from communication-IC, then compare with 20% of rated apparent power, when no more than 20% of rated power, implement low-section energy-measure subroutine, or else go to implement high-section energy-measure subroutine, during it, implement storaging-refreshing subroutine at any time, and then implement display subroutine, to this end one time of power measurement, down repeat this time, so that the power of these two sections can respectively cumulate continuously. The software design to multi-function is: Keys used for; Buzzer's stopping and the ringing is controlled by high-low level of MCU-pin; Communication between MCU and communication-IC is based on the SPI serial communication subroutine; Storaging and refreshing is based on the IIC serial communication subroutine, real-time clock also need that real-time clock can be ordered; Clearing is controlled by the high-low level of MCU-pin.At present, the meter test results have indicated that it can complete the requirements of function and achieve the full range precision balance and accurate measurement.