| 摘要 |
<p>Metering kWh is an electrical system is accomplished by generating pairs of analog signals representing current and voltage variables. A comparator compares an analog signal which is proportional to the voltage in the system with a relatively high frequency triangular waveform. The Output of the comparator, which is a pulse-width modulated signal having a pulse duration proportional to the amplitude of the voltage in the system, is multiplied by a signal which is proportional to the current in the system. The output of the multiplier is integrated to thereby provide a signal which is proportional to the energy consumed in the system. The output of the integrator is converted to a pulse train having each pulse proportional to the kilowatt hours consumed in the electrical system. A mechanical accumulation and display means records the total energy consumed and is driven in response to the output of the analog-to-pulse rate converter. The pulse output of the converter closes a switch which couples a relatively large amount of current to a motor winding which advances the mechanical display. Power for the active elements in the system, including the drive for the mechanical display, is derived from the system being measured by means of an internally provided power supply. Error correction is provided by means of a switching means which reverses the phase of the triangular waveform and the first analog signal by reversing the connections of these signals to the comparator.</p> |
