| 摘要 |
PURPOSE:To perform more accurate measurements than analog devices, by a tester wherein power of an electric power system is measured in a digital manner and average power measured at the same time by a wattmeter to be tested is calculated by the same device used for the digital measurement, thereby to display a difference between both the results. CONSTITUTION:A microcomputer 8 judges the presence or absence of a level change of a pulse signal from a test pulse detector 6 every when a pulse signal from a reference time generator 5 is input to a parallel data detector 7. When the level change is detected, a sample value is latched from a point between A-D converters 3, 4 and the detector 7. Then the product of voltage and current is calculated, thus obtained products are added and the times of such addings are counted. The measurement is completed after given times of operations are performed. Average power obtained by this measurement within a certain measuring time is calculated on the basis of data stored in the microcomputer 8. The microcomputer 8 displays in a digital manner a difference between thus calculated average power and average power measured by a wattmeter 10 to be tested. By so doing, a reference wattmeter is not required and the more accurate measurement can be performed comparing with the prior device in which power is computed by multiplying in an analog manner. |
