The Design Of A Portable Multifunction Calibrator Of Electrical Transformer

The electrical transformer used for measurement and protection is an important instrument in the electrical system, and its scheduler calibration cannot be neglected. So the Research of portable transformer calibrator, which used for field calibration, is useful and even significant.This paper mainly deals with the research of a kind of portable on-line calibrator of CT and PT based on MSP430, and which is a kind of ultra low-power mixed signal micro-controller. This calibrator is characterized by high accuracy, low power consumption, and multifunction. The whole paper was divided into hardware section and software section to expound the design principle and implementation in detail.In the hardware section, the paper introduces the whole hardware system briefly at first, which includes MSP430F149 microcontroller, LCD module, real time clock module, EEPROM, keys, power management module, serial communication module and signal regulation module. Functions of the signal regulation module were introduced, and function of auto-range-adjust was analysis specifically. The good performances of the MSP430 would be introduced specifically later, and the process of data acquisition, calculation, message save and result display, which was achieved by the MSP430 and some other relevant circuits, would be analysis. A new power management module of the battery was discussed at last, and charge & discharge circuit, battery gas gauge circuit, and the DC/DC transform circuit in the module was introduced. From the choice to the design of the power management, the ultra-low power consumption of the device was emphasized in this section.In the software fraction, this paper discussed a new method of the programming, which could trace the signal frequency change by the interrupt function of the MCU. And the design of multifunctional matrix keys was introduced, as the hardware resource was saved and the management efficiency rose by this design. The calculation method of the digital signal was deduced later. Then the paper provided a new method of the interface design, which the I/O pins were used to couple the interface bus sequence. Some experiment result were showed at last, and form the result the conclusion could be made that the measurement accuracy level reaches 0.5%, then error sources were analysis based on the results.Finally, in order to get rid of the disadvantages of foreground/background system, another scheme is given. In this scheme, uC/OS-II—a real-time embedded operating system kernel—becomes the core, all the functions of the calibration device system are partitioned into some tasks, and every task would be managed well by the MSP430 well. If the scheme can be applied into the system, the stability and reliability will be enhanced remarkably.