528 ELECTRICAL MEASUREMENTS 



The teeth of the escapement wheel are radial, so there is no 

 interchange of power between the two elements. 



When a load is thrown on, the main disc begins to revolve and 

 the auxiliary disc tends to assume its ultimate position at once. 

 However, the escapement mechanism prevents this, and the 

 deflection increases step by step at a rate dependent on the rapid- 

 ity of oscillation of the escapement; that is, on the velocity of the 

 main disc. If the load is doubled the escapement oscillates twice 

 as fast, but as the pointer must move twice as far the ultimate 

 deflection is attained in the same time. By changing the timing 

 gears the maximum deflection may be reached in 1, 2, 5, 15 or 

 30 min. as desired. When the load decreases, the main pawl 

 drags over the ratchet wheel and the driving arm moves away 

 from the dog, leaving the pointer at its maximum deflection. 



By raising the trip, which is protected by a separate seal, the 

 pointer may be set back to zero without opening the meter. 



During calibration the main pawl is raised, thus disconnecting 

 the escapement. The instrument is then calibrated like an ordi- 

 nary wattmeter by altering the length of the spiral spring and the 

 zero adjustment. 



The instrument is reset each month by the meter reader and 

 leaves no record of its former indication, and there is no way of 

 telling the hour of the day when the maximum occurred. 



References 



1. "Electricity Meters," H, G. SOLOMON, Charles Griffin & Co., London, 

 1906. 



2. "Electricity Meters," C. H. W. GERHARDI, Electrician Printing and 

 Publishing Co., London, 1906. 



3. "Electrical Meters," C. M. JANSKY, McGraw-Hill Book Co., 1913. 



4. "Electrical Measurements and Meter Testing," D. P. MORETON, 

 Frederick J. Drake & Co., Chicago, 1915. 



5. "Electrical Meterman's Handbook," published by National Electric 

 Light Association, 1915. "Code for Electricity Meters," Association of 

 Edison 111. Co., Nat. Elect. Light Assoc., second edition, 1912. 



6. "Die Elektrizitatszahler," R. ZIEGENBERG, "Handbuch der Elektro- 

 technik II Sechste Abteiling," Leipzig, 1908, S. HUZEL. 



7. "Electrical Instruments and Meters in Europe," H. B. BROOKS, 

 Department of Commerce and Labor, Washington, D. C., 1913. 



8. "A Comparative Study of American Direct-current Watt-hour 



