| 摘要 |
An AC analog to digital converter provides a one step conversion of an alternating (AC) analog voltage to a digital number proportional to the amplitude of the input analog voltage. A zero crossing detector responsive to the analog input voltage actuates switching logic to supply one-half cycle of the input voltage to a conventional integrator. Control logic, at the initiation of the next successive half cycle following the half cycle of integration of the AC input, switches a reference voltage of appropriate polarity and predetermined amplitude to the integrator for discharging the integrator to a zero voltage output level. The control logic gates a clock pulse train to a counter during the time interval of discharge of the integrator and inhibits further gating of the clock pulses to the counter upon integration back to zero value. The count accumulated in the counter during the discharge interval is proportional to the input magnitude and affords a direct digital output representing the analog amplitude of the input. The reference voltages comprise absolute DC reference voltages or DC voltages which are compensated for variations in the AC signal source, the latter being provided by an integrate and hold circuit operated by the same switching and control logic outputs as utilized in the converter itself. |
