| 摘要 |
<p>An electronic meter for measuring V2hr in an electrical system includes a center tapped transformer for deriving two analog signals proportional to a detected voltage in the system with the analog signals being 180.degree. out of phase with respect to one another. A comparator compares a relatively high frequency triangular signal with a selected one of the analog signals with the output of the comparator driving a switch which acts as a multiplier. When a comparison exists the switch couples one of the analog signals to an integrator, and when a comparison does not exist, the switch couples the other analog signal to the integrator. The output of the comparator is a pulse width modulated signal having a time duration which is proportional to the amplitude of the detected voltage in the system, and the signal coupled to the integrator is a chopped analog signal having an amplitude proportional to the amplitude of the voltage in the system and a time duration proportional to the magnitude of the voltage. Accordingly, the integrator integrates a signal which is proportional to V2. At the output of the integrator a signal is generated which is proportional to V2hr. This signal is converted to a pulse train having a frequency proportional to amplitude of the output of the integrator. Offset correction is provided by means of up/down integration averaging wherein the input signal to the comparator is switched each time an output pulse is generated.</p> |
