IMPROVED AUTOZEROING APPARATUS AND METHOD FOR A COMPUTERIZED TOMOGRAPHY DATA ACQUISITION SYSTEM

摘要

The invention discloses an automatic reset device for correcting a displacement error in a data acquisition subsystem (DAS) scanner computerized axial tomography (CAT). DAS subsystem includes a floating point amplifier for applying discrete amplification factors, or gain range segments, to an analog input before converting them to digital in an analog / digital converter. A digital autozero circuit is connected to the output of the analog / digital converter and adds a digital displacement value to each sample of the analog / digital converter during the acquisition of data for correcting the net displacement errors in the sub DAS system. Separate memory latches are used to memorize the displacement values ​​for each gain range segment, and the displacement value used for correcting each sample corresponds with the range segment gain used for said sample. During a reference interval for automatic reset, a reference voltage is applied to the DAS subsystem, and the displacement values ​​are crumbs modified to force the output of the A / D converter to be in agreement with the reference voltage.