. The principles and practice of roentgenological technique . desired tap on the autotransformer is selected, the variation beingby two kilovolt steps and continuous, i. e.,the voltage may be changed with the tube inoperation without interrupting the currenteven momentarily. This t3pe of control in-sures practically constant penetration, regard-less of the vacuum of the tube, a feature whoseimportance cannot be overestimated. The po-tential once set, only the time of exposureneed be changed to meet varying tube con-ditions. The switch placed where most accessible tothe right hand, opens automa
. The principles and practice of roentgenological technique . desired tap on the autotransformer is selected, the variation beingby two kilovolt steps and continuous, i. e.,the voltage may be changed with the tube inoperation without interrupting the currenteven momentarily. This t3pe of control in-sures practically constant penetration, regard-less of the vacuum of the tube, a feature whoseimportance cannot be overestimated. The po-tential once set, only the time of exposureneed be changed to meet varying tube con-ditions. The switch placed where most accessible tothe right hand, opens automatically when re-leased. By throwing it clear to the left, how-ever, it catches in the on position. Throw-ing it to the right throws a floor push buttoninto circuit for use in fluoroscopy. Immediately in front of the voltage-controlwheel is a small lever by which resistance inthe circuit may be regulated. The first pointin the extreme left eliminates all the resist-ance, giving the full auto transformer controlcharacteristics. Point two inserts a small pro-. FiG. 52.—Control panel of converter unit. 1. Alilliammeter. 2. Kilovoltmeter and polarit\ indicator. 3. Tube regulating switch. 4. Ammeter switch. 5. Coolidge control switch. 6. Motor switch. 7. Radio flue switch. 8. Auto transformer control switch. 9. Ballast resistance switch. tective or ballast resistance for treatment workwith a Coolidge tube. Point three is intendedprimarily for raising the vacuum of hydrogentubes. Point four is suitable for fluoroscopy, and the resistance inserted is such that it isimpossible to draw more than ten milliamperesthrough the tube. ^ The voltmeter, serves both as an indicatorof penetration and phase, since it reads onlywhen the motor is in step. This meter is soconnected into the circuit that the voltage tobe applied to the tube can be regulated andread before the tube is liarhted.
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectradiogr, bookyear1920
