| 摘要 |
PURPOSE:To make it possible to measure the tube current accurately by providing a sample hold circuit to sample and hold the output of the first detecting circuit with the output timing of the pulse voltage of the third detecting circuit. CONSTITUTION:A signal S19 proportional to the tube current is output from a sample hold circuit 10. The signal S19 is converted into a signal of an adequate level responding to the length of a high voltage cable by a signal converting circuit 39, and used for each control circuit as a measurement tube current signal. A feedback is carried out as the practical measurement of the tube current to a filament heating circuit 30, the signal is compared with the tube current set value in the filament heating circuit 30, and the heat value is controlled responding to the error, making the error zero. Then the measurement tube current signal input to an integral circuit 40 is time-integrated into an mAs value, and when the mAs value exceeds the preset mAs value, the X-ray exposure stopping signal is output to an inverter control circuit 9, to finish the exposure of the X rays. In such a way, it is made possible to detect the tube current accurately.
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