x CONTENTS 



I'M.*. 



meters Hot-wire Voltmeters ELECTROSTATIC INSTRUMENTS 

 The Attracted-disc Electrometer The Quadrant Electrometer 

 The Mechanical and Electrical Zeros General Considerations- 

 Electrostatic Voltmeters Use of a False Zero Reading Condenser 

 Multipliers for Extending the Range of Electrostatic Voltmeters 

 THE SPARK-GAP METHOD OF MEASURING HIGH PEAK VOLTAGES 

 POTENTIOMETER ARRANGEMENTS Poggendorf s Method of Com- 

 paring a Potential Difference and an Electromotive Force The 

 Potentiometer Practical Arrangement of the Potentiometer 

 Low-scale Arrangement Wolff Potentiometer The Brooks De- 

 flection Potentiometer The " Thermokraftf rei " Potentiometer 

 Effect of Thermo-electromotive Forces Application of the Poten- 

 tiometer to Alternating-current Measurements The Drysdale 

 Phase Shifter The Drysdale-Tinsley Alternating-current Potenti- 

 ometer STANDARD CELLS The Clark Cell Board of Trade Cell 

 The H Cell Materials Used in Standard Cells The Weston or 

 Cadmium Cell The Weston Secondary Standard Cell Precau- 

 tion in Using Standard Cells. 



CHAPTER VI 



POWER MEASUREMENT 303 



The Electrodynamometer Wattmeter Heating Losses in Watt- 

 meters Compensation for Energy Loss in the Potential Circuit 

 Grouping of Instruments Errors due to Local Fields Voltage 

 between Current and Potential Coils The Effect of Reactance in 

 the Potential Circuit Compensation for the Inductance of the 

 Potential Circuit Effect of Mutual Inductance between Fixed and 

 Movable-coil Circuits Eddy-current Errors OTHER METHODS 

 OP MEASURING POWER The Three Dynamometer Method The 

 Three Voltmeter Method The Split-dynamometer Method 

 Potier Method for Power Measurement The Electrostatic Watt- 

 meterSources of Error Ryan Power Diagram Indicator 

 POWER MEASUREMENT IN POLYPHASE CIRCUITS Blondel's Theo- 

 remDesignation of Wattmeter Terminals Two-phase Three- 

 wire System Two-wattmeter Method The Polyphase Watt- 

 meterThree-phase Power Measurement by Three Wattmeters 

 The Y-box Four-wire Three-phase System. 



CHAPTER VII 



MEASUREMENT OP INDUCTANCE AND CAPACITY 341 



STANDARDS OP INDUCTANCE Standards of Mutual Inductance-^ 



ampbell Fixed Standard of Mutual Inductance Variable 



Mutual Inductances Ayrton and Perry Inductor Brooks Vari- 



* Inductor-STANDARDS OF CAPACITY Secondary Air Conden- 



