526 ELECTRICAL MEASUREMENTS 



The essential portions are : a system of cyclometer type wheels 

 actuated by a solenoid which is controlled by the watt-hour meter ; 

 an arrangement for automatically advancing the paper tape after 

 each record (about % in.), and at the same time moving along 

 the copying ribbon necessary for the printing; an electrically 

 operated platen for taking the impression. The platen is con- 

 trolled by a contact-making clock in a separate case and is 

 operated every half hour. 



In addition, there is a fourth type wheel, in line with the other 

 three, which prints the hours. Every half hour the contact- 

 making clock closes the circuit and causes the printing platen 

 to be drawn up. At the same time it sets in motion a system of 

 levers and gears by which the hour wheel is turned. At down 

 stroke of the armature the paper tape and the copying ribbon are 

 advanced. 



To actuate the printometer, a contact device is placed on one 

 of the shafts of the register of the watt-hour meter so that it 

 closes the circuit to the cyclometer solenoid after the appro- 

 priate number of revolutions of the meter disc. The circuit is 

 so arranged that it is made by the contact device and quickly 

 broken by the plunger in the solenoid at the end of its stroke. 

 The arcing is thus transferred to very substantial contacts and 

 friction is avoided. The current is kept out of the solenoid 

 except when it is actually operating. 



The record obtained is shown in Fig. 312. By subtracting the 

 successive readings the demand during any specified half hour 

 may be obtained. 



Westinghouse R.O. Demand Indicator. This instrument is a 

 combined watt-hour and watt-demand meter for use on alter- 

 nating-current circuits. The kilowatt-hours are registered on 

 four dials, as usual, while the demand is shown by a long pointer 

 which moves over a fifth dial graduated in watts or kilowatts. 



The mechanism is such that when a load is thrown on, the watt- 

 meter attains the corresponding deflection only after a predeter- 

 mined time, for example 15 min., the rate of increase of the 

 deflection being controlled by the watt-hour meter. 



Fig. 313 shows in a diagrammatic form the essential features of 

 the registering mechanism. The main disc is that of an ordinary 

 induction watt-hour meter. By means of the worm it actuates 



