| The precision of power meters is very important. So calibration instrument of power measurement which to test precisions of this kind of instruments emerges as the time require. It's very important for the power test and power supply departments. The calibration instrument of power measurement should have the ability to measure electrical parameters and vefify other power meters. After analyzing the design schemes of this kind of products demestic and abroad, special power chip is adopted to measure electrical parameters and the hardware and software design become compact. Special chip samples voltage and current and calculate electrical parameters. Mcu reads these parameters from it and does data processing. The calibration instrument based on CS5460A can measure the virtual value of voltage and current, active power and power factor. The enganced one based on ADE7758 can measure reactive power, visual power and frequency yet. Through scaning the key state, the program switch to the corresponding subprogram to display and save these parameters, calibrate other power meters and communicate with host computer. We select small real-time operation system μC/OS-Ⅱafter analyzing how to design program in foreground and background system. Firstly, μC/OS-Ⅱis ported to ARM mcu and then driver for each module are designed. At last, prioritiy for each task are confirmed and application programme is designed. After the compare of the two different ways, the task scheduling method of real-time operation system is understood clearly. And advantages of using real-time operation system in design of instruments are summed up. The characteristic of real time and stability of the system is enhanced, and new functions are easily enlarged. At last, error analyses and experiment results are provided. From the results, we can see the system achieve the expected request and have practicality.
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