| 摘要 |
<p>An autozeroing apparatus is disclosed for correcting the offset error in a computerized axial tomography (CAT) scanner data acquisition subsystem (DAS). The DAS includes a floating point amplifier for applying discrete amplification factors, or gain range segments, to an analog input before conversion to digital in an A/D converter. A digital autozero circuit is connected to the output of the A/D converter and adds a digital offset value to each A/D converter sample during data acquisition to correct for the net offset errors throughout the DAS. Separate storage latches are included for storing offset values corresponding to each gain range segment, and the offset value used for each sample correction corresponds to the gain range segment used for that sample. During an autozero reference interval, a reference voltage is applied to the DAS and the offset values are updated so as to force the corrected A/D converter output to agree with the reference voltage.</p> |
