Text extracted from opening pages of book: INTERNATIONAL SERIES IN PHYSICS F. K. RICHTMYER, CONSULTING EDITOR ELECTRICAL MEASUREMENTS INTERNATIONAL SERIES IN PHYSICS F. K. RICHTMYER, Consulting Editor Backer and Goudsmit ATOMIC ENERGY STATES Clark APPLIED X-RAYS Condon and Morse QUANTUM MECHANICS Curtis ELECTRICAL MEASUREMENTS Davey CRYSTAL STRUCTURE AND ITS APPLICATIONS Edwards ANALYTIC AND VECTOR MECHANICS Eldridge THE PHYSICAL BASIS OF THINGS Hardy and Perrin THE PRINCIPLES OP OPTICS HamwellandLimngood EXPERIMENTAL ATOMIC PHYSICS Houston PRINCIPLES OP MATHEMATICAL PHYSICS Hughes and DuBridge PHOTOELECTRIC PHENOMENA Hund HIGH-FREQUENCY MEASUREMENTS PHENOMENA IN HIGH-FREQUENCY SYSTEMS Roller THE PHYSICS OP ELECTRON TUBES Morse VIBRATION AND SOUND Pauling and Goudsmit THE STRUCTURE OF LINE SPECTRA Richtmyer INTRODUCTION TO MODERN PHYSICS Ruark and Urey ATOMS, MOLECULES AND QUANTA Slater and Frank THEORETICAL PHYSICS JFAlte INTRODUCTION TO ATOMIC SPBCTHA Williams MAGNETIC PHENOMENA ELECTRICAL MEASUREMENTS Precise Comparisons of Standards and Absolute Determinations of the Units BY HARVEY L. CITRUS, PH. D. Principal Physicist at ( Ke Bureau of Standards FIRST KDITION McGRAW-HTLL BOOK COMPANY, TNG. NEW Y011K AND LONDON 1937 COPYRIGHT, 1937, BY THE MrGiuw-HiLL BOOK COMPANY, INC PRINTED IN THE UNITED HTATKH <> AMERICA All rights reserved This book, or parts thereof, may not bereptoduced in any form mthout per mi mo n of the publishers THE MAPLE PRBR8 COMPANY, YORK, PA. To MY WIFE PREFACE This book presents those methods which are capable of giving precise results in absolute electrical measurements, and gives the details of methods which permit the accurate comparison of electrical standards. The increasing demand for precision in electrical measurements has emphasized the need for a text that places special emphasis on accuracy of measurement. This is especially the case in regard to those absolute electrical measure ments which are used to establish the values of the electrical units. This book has been prepared to make available the technique that has been developed in this field. The discussion of the methods is based on the assumption that an accuracy of one part in a million is desirable in every type of measurement. This accuracy was selected as the most precise that was demanded in any electrical measurement. However, since the preparation of the manuscript was begun, there has been a pronounced increase in the precision of measurements in several fields. Comparisons of resistance standards are now made to one part in ten million, and the same can be said con cerning standard cells. Standards frequencies are now dissemi nated which have this accuracy. The need for this extreme accuracy is exceptional, but its use indicates the trend in electrical measurements and shows that an accuracy of one part in a million should be the goal in most fields. Moreover the use of the same standard of accuracy in all fields of electrical measurements greatly facilitates comparisons between them. The original plan of the book contemplated including only those methods which are directly concerned with the establishing of the electrical units. However, the desirability of including the comparisons of standards soon became apparent, as there are no texts available which indicate the precautions that must be observed when comparisons are to be made with an accuracy of a part in a million, and such comparisons must frequently be made in the absolute methods. Hence the final plan includes, for each of the electrical quantities, at least one method for vii Vlil PREFACE intercomparing two different values of this quantity. An attempt is made, not to include all the methods that can be used in precise comparisons, but to give, under each heading, one or two methods that will give accurate results. In a few cases, where suitable methods were unknown to me, new methods have been outlined that I believe are capable of giving accurate results. In such ca
