Electrical Measurements in Practice

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Originally published in 1917. PREFACE The subject of electrical measurements has received much attention in the literature of electrical engineering. In general, however, the treatment has been from a theoretical or academic point of view. In this volume the author has endeavored to present the subject in a simple, practical manner and from the standpoint of engineers who are actively engaged in making measurements, tests and investigations in the electrical industry. All classes of measurements that the laboratory and testing engineer is ordinarily called upon to make have been covered. The method of treatment and part of the material is the same as to the Fourth that in the authors contribution on this subject Edition of the Standard Handbook for Electrical Engineers. Instruments must naturally form a prominent part of any discussion of electrical measurements, but detailed descriptive matter pertaining to commercial instruments has been limited to those instruments in most general use and without which the book would be obviously incomplete. Maximum demand meters have, however, been described rather extensively because they are a comparatively recent development. A short chapter has also been devoted to curve-drawing instruments because of their important part in commercial measurements and in laboratory investigations. NEW YORK CITY, June, 1917. Contents include: PAGE PREFACE V CHAPTER I INTRODUCTORY 1 Measurements Units Fundamental or Absolute Electrical Units Practical Units and Standards Relation between Absolute and Practical Units Primary and Secondary Standards Precision Precision of Commercial Measurements General Precautions in Electrical Measurements. CHAPTER II GALVANOMETERS 11 General Mounting CHARACTERISTICS OF GALVANOMETERS Sensitivity and Constants Figure of Merit Factor of Merit Damping Critical Damping Period GALVANOMETER SHUNTS Plain Shunts Universal Shunts SELECTION OF A GALVANOMETER Ruggedness Stability of Zero Resistance Period Damping Magnetic Impurities Sensitivity CONTINU- OUS CURRENT GALVANOMETERS Tangent Galvanometer Sine Galvanometer Kelvin Galvanometer Broca Galvanometer DArsonval Galvanometers Portable DArsonval Galvanometers Einthoven String Galvanometer Ballistic Galvanometers ALTERNATING CURRENT GALVANOMETERS Electrodynamometer Galvanometers Thermal Galvanometers Vibration Galvanometers Rectifiers GALVANOMETER DEFLECTIONS Reflectinggalvanometer Deflections Galvanometers as Detectors Galvanometer Scales. CHAPTER III CONTINUOUS E.M.F. MEASUREMENTS 37 Unit of E.m.f...