| 摘要 |
A method and an apparatus are disclosed for converting an analog input signal having either a positive or negative polarity into a digital output signal indicating the magnitude and polarity of the input signal. Amplifier offset voltages and dynamic hysteresis in the comparator are compensated automatically and a zero reference is established automatically to provide a corrected output. A compensation capacitor and an integrating capacitor are selectively charged. A reference signal is integrated to measure the magnitude of the difference between the integrator offset voltage and the comparator threshold. A digital representation of the time required to measure the difference between the integrator offset voltage and the comparator threshold is stored. The compensation capacitor and the integrating capacitor are again selectively charged. The analog input signal is then integrated for a fixed time. The reference signal is integrated for a time equivalent to the digitally stored time. The time required to continue the integration of the reference signal to a predetermined voltage is then measured. The measured time is converted into a digital output signal representative of the magnitude and polarity of the analog input signal.
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