| 摘要 |
PURPOSE:To make it possible to display an integrated amount of power in the case where it is small and display of an integrated power high resolution by a method wherein CPU switches over a display resolution automatically on the basis of an integrated value and time of integration. CONSTITUTION:AC voltage (v) and current (i) are inputted to A/D converters 21 and 22 through input circuits 11 and 12 and converted into digital signals, respectively. DSP(digital signal processor) 30 taking in these signals determines an instantaneous power and an integrated power for a prescribed time on the basis of the two input data and transfers them to CPU 40. The CPU 40 determines the position of a decimal point and others on the basis of data on the integrated power and a time of integration and a display digit of a display device 50 and then displays the value of the integrated power in the display device 50. On the occasion, the CPU 40 changes the digit when the time of integration needs the change of the digit, while it determines the position of the decimal point and unit on the basis of the data on the integration when the time does not yet reach the time of integration necessitating the change of the digit, and makes the display device 50 display them. In other words, the CPU can switch over a display resolution automatically and display an integrated electric energy with a high resolution. |
