| 摘要 |
<p>A signal proportional to the load current is integrated during the positive (or negative) half-cycles of the supply voltage. Whenever the integrator (7) output crosses the boundary of two limits, a reference voltage (with the appropriate polarity) is also integrated to bring the integrator output inside the two limits. During the reference voltage integration time, the pulses generated by a voltage to frequency converter (3) are used to increment or decrement a counter (9) according to the polarity of the reference voltage. The frequency of the voltage to frequency converter is made proportional to the supply voltage. After any period of time, the counter content changes by an amount proportional to the watt-hour consumed during this period.</p> |
