| 摘要 |
PURPOSE:To reduce the size of the title watt-hour meter by converting an AC voltage and current into quantized digital voltage and current value data and constituting the main body of the meter of a digital circuit. CONSTITUTION:A/D conversion circuits 12 and 13 driven by an oscillator 17 respectively convert an AC voltage (v) and current (i) into quantized digital voltage and current value data and a multiplier 14 finds power value data by performing multiplication on the data. An adder 15 finds an integrated watt-hour value by successively adding the power value data to each other and the watt-hour value is displayed on a watt-hour displaying section 16. A shift register 23, on the other hand, successively stores the power value data outputted from the multiplier 14 and an adder 24 takes the sum of all stored data and outputs the sum to a register 19 for storage. A subtraction counter 20 performs subtraction on the value stored in the register 19 in accordance with the oscillating period of an oscillator 18 while the counter 20 loads the values by inverting the value at every prescribed period and, when the count value becomes '0', inverts its output. The output of the counter 20 becomes a meter constant pulse. Since this electronic watt-hour meter can be constituted of a large-scale IC by using a digital circuit as a main body in such a way, the meter can be reduced in size. |
