. A text-book of radiology . er one carries the fixed platinumcontact—the other point being mounted on the back ofthe iron block or armature—H. The lower screw is for regulating the tension, and byturning to the left the spring carrying the armature ispulled back, causing the contacts to be more tightlypressed together. When both of the screws are slackened the armatureface is about one-eighth of an inch from the end of thecore of the coil. 73 74 TEXT-BOOK OF RADIOLOGY. The adjustment of this break requires some practice,as some coils require a different adjustment to get thebest result. As go
. A text-book of radiology . er one carries the fixed platinumcontact—the other point being mounted on the back ofthe iron block or armature—H. The lower screw is for regulating the tension, and byturning to the left the spring carrying the armature ispulled back, causing the contacts to be more tightlypressed together. When both of the screws are slackened the armatureface is about one-eighth of an inch from the end of thecore of the coil. 73 74 TEXT-BOOK OF RADIOLOGY. The adjustment of this break requires some practice,as some coils require a different adjustment to get thebest result. As good a method as any is the following : — Both screws being slackened, and the platinum facesC C being nicely smoothed and flattened with a fine file,the upper screw B is turned to the right until theplatinum contacts are almost touching—leaving a spacebetween equal to the thickness of a visiting card. Theclamping nut on B is now run up against the pillar, so asto prevent this screw turning while the coil is in Fig. 30. Apps Contact Breaker (from Wrights Induction Coil). The current being turned on, the lower or tensionscrew T is slowly turned to the left, and the moment thecontacts come together the current flows and the coil isin action, very gently at first. As the tension is increasedthe output of the coil increases, but the interrupter worksmore slowly owing to the fact that the core of the coilmust become more highly magnetised before its pull uponthe armature is sufficient to separate the platinumcontacts. This form of interrupter is used only on portable coilsor those taken abroad on a campaign for which it is very MERCURY INTERRUPTERS. 75 suitable from its simplicity, and the fact that almostevery case can be radiographed by the aid of a coil fittedwith it, but of course in the more difficult cases theexposure has to be inconveniently long. It works at its best with a current of from 12 to 24volts, and the amount of inverse current is so small as tobe qu
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