| 摘要 |
PCT No. PCT/GB92/01664 Sec. 371 Date Sep. 28, 1993 Sec. 102(e) Date Sep. 28, 1993 PCT Filed Sep. 11, 1992 PCT Pub. No. WO93/06493 PCT Pub. Date Apr. 1, 1993.A method for generating a product of signals proportional to the voltage of an electrical supply and the current flowing through a load connected thereto, comprises the steps of deriving a first signal proportional to the said supply voltage, deriving a second signal proportional to the load current, frequency modulating two constant frequency carrier signals by the said first and second signals to produce third and fourth signals respectively, normalizing the third and fourth signals with reference to frequencies corresponding to zero voltage and zero current, and multiplying the two normalized third and fourth signals to form a product signal which is proportional to the power being absorbed by the load connected to the electrical supply. The third and fourth signals comprise pulse trains whose instantaneous pulse repetition rate is proportional to the voltage and current. Apparatus is described for performing this method. A 555 timer device is employed for voltage to frequency conversation. A microprocessor is employed for multiplying the fifth and sixth signals and is programmed to compute therefrom not only the apparent power but also the apparent instantaneous power, the real energy and real power and also the reactive energy and reactive power supplied to the load. |
