MEASUREMENT OF ENERGY 59 



its pressure coil forms one of the arms of an artificial star (all the 

 arms being of equal resistance), the connections being as shown in 

 Fig. 41.* Again, two meters connected as in the two- wattmeter 

 method of power measurement may be combined into a single 

 instrument, the rotating parts being mounted on a common axis; 

 this has the advantage of compactness as compared with two ordinary 

 single-phase meters. 



* If the meter is arranged to give correct readings on a single-phase circuit, its 

 millings when transferred to u three-phase circuit and connected aa above give one- 

 third of the total energy. 



