. The American journal of roentgenology, radium therapy and nuclear medicine . OENT-GENOL., April, 1919, vi, 175. 3-8 Standardization of the Measurement of Tube Potential these tests are illustrated herewith ingraphic form. Figure 10 shows the calibration of thespark gap used. The source of electricalenergy for this experiment was a machinemaking actual metallic contact during 85electrical degrees—in other words, prac-tically a pure pulsating sine wave form. The A. I. E. E. specification spheregaps were used, and the maximum sparkpotential which has been adopted for usewith them was taken as a
. The American journal of roentgenology, radium therapy and nuclear medicine . OENT-GENOL., April, 1919, vi, 175. 3-8 Standardization of the Measurement of Tube Potential these tests are illustrated herewith ingraphic form. Figure 10 shows the calibration of thespark gap used. The source of electricalenergy for this experiment was a machinemaking actual metallic contact during 85electrical degrees—in other words, prac-tically a pure pulsating sine wave form. The A. I. E. E. specification spheregaps were used, and the maximum sparkpotential which has been adopted for usewith them was taken as a standard. The point curve must not be confused inany way with another standard whichis occasionally referred to in the literature,namely, the needle point gap formerlyused by the A. I. E. E. as a standard ofhigh potential. The values given in tablesfor this needle point gap apply only to agap made with needles— and further theyapply only for alternating current. Theycannot be cross applied to pulsating directcurrent without errors which may reach ashigh as 50 per Fig. to. No standard specifications have everbeen worked out for the so-called pointspark gap commonly used in x-ray was therefore assumed that r,s inch rod,beveled to a conical 60 degree point, andslightly blunted, would correspond to therough average of the various spark gaps incommon use. The object in slightly blunting orrounding the point is that no user of x-rayapparatus takes pains to sharpen the pointson his spark gap periodically, and theytherefore become rounded through it seems quite logical to start byslightly rounding such points. Either of the curves given may be used(with appropriate reservations for mac-curacies) for translating spark gap read-ings on x-ray machine into kilovolts ofpotential. A kilovolt is a perfectly definite,measureable quantity. But an inch or acentimeter ol spark gap is emphaticallyriot a definite thing, even when measuredwith all possible precautions.
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