| 摘要 |
PROBLEM TO BE SOLVED: To test the LSI of an electronic watthour meter easily and quickly without requiring any special apparatus, e.g. a high resolution expensive AC signal generator or a V/F converter. SOLUTION: A DC voltage corresponding to the output voltage from a DC power supply circuit 21 to be measured is subjected to pulse width modulation by a modulation circuit 34 in a large scale integrated circuit (LSI) 22 of a watthour meter. An external multiplier 25 multiplies a modulation output by a DC voltage corresponding to an output current from a DC power supply circuit 24 to be measured to produce an electric energy which is outputted in the form of a voltage. DC component is then extracted from the voltage through a DC filter 28 and delivered through an internal multiplier circuit 36 in the watthour meter LSI 22 to the V/F converting section 33. The V/F converting section 33 integrates and converts the DC component into a frequency to produce a power pulse. Pulse width of the power pulse is measured by means of a counter 29 and a conversion frequency is calculated by a controller 27. |
