. Radiography and radio-therapeutics . Fig. 72.—Arrangement of valve tubes in circuit. (A. C. Cossor, Ltd.)Diagram I. shows the correct method of connecting for single valve II. shows the conect method of connecting for two valve tubes in III. shows the correct method of connecting in order to ascertain equivalent sparklength or to work up (to harden) the valve tube. When intensive currents are used it may be necessary to put a valvetube on each pole or even to have 6 or 8 valve tubes in series. By usingvalve tubes the amount of inverse current can be practically ab
. Radiography and radio-therapeutics . Fig. 72.—Arrangement of valve tubes in circuit. (A. C. Cossor, Ltd.)Diagram I. shows the correct method of connecting for single valve II. shows the conect method of connecting for two valve tubes in III. shows the correct method of connecting in order to ascertain equivalent sparklength or to work up (to harden) the valve tube. When intensive currents are used it may be necessary to put a valvetube on each pole or even to have 6 or 8 valve tubes in series. By usingvalve tubes the amount of inverse current can be practically abolished when. -i:2l_ Fig. 73.—Zenith valve tube. (A. E. Dean.) medium currents are employed, but when very heavy currents are used it isnot possible, or hardly ever possible, to abolish it. There are several other varieties of valve tube of more recent construc-tion. The various types described are useful on installations of medium 86 KADIOGRAPHY power, but if they are used on the more powerful iustallations of recent date,thev soon begin to vary in hardness, and add considerably to the difficultiesof the radiographer. This is particularly noticeable when the installation isused alternately for short exposures and long ones. The balance of thevalve tube is disturbed, and it will require almost constant regulation. Itshould be pointed out that when valve tubes are used they require nearly asmuch regulation as the X-ray tube. When the X-ray tube is kno^vn to beright and the results are not satisfactory, attention should be paid to thecondition of the valve tube. Method of Detecting Reverse (Inverse
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