| 摘要 |
<p>The system includes a resistance (R) for monitoring the current of the image amplifier (21) for the display of the X-ray installation (19). Alternatively, the output of photo-electric a cell (22) can be used. A pulse, synchronised to the voltage output of the power supply unit (18), triggers a saw-tooth voltage generator (2). When the sawtooth reaches a preset level, a comparator (3) triggers a multivibrator (4) which generates a pulse of fixed duration. This pulse, applied to a switch (1), samples the current waveform at its peak to tive a shaped sample. If the amplified voltage is less than a limit, set by reference voltage generator (11), a comparator (13) causes a servo-motor (17) to drive a variable auto-transformer in the power supply unit (18) so as to increase the X-ray intensity. Conversely, if it is below a limit set by reference generator (12), the motor (17) reduces the intensity. If the X-ray tube itself contains a device for controlling intensity, the limits (12,13) are set so that the servo system operates only outside the range of this device.</p> |
