GRAPHIC RECORDING INSTRUMENTS 



557 



The large vertical cylinder at the left is a laminated soft iron 

 shield. The working parts consist of two substantial dynamo- 

 meter wattmeters, both movable coils being rigidly attached to 

 the same stem which is suspended by a steel torsion wire. The 

 lower end of the stem is centered by a small steel pin which 



FIG. 340. Curve-drawing polyphase wattmeter and record, General 



Electric Co. 



passes freely through a ring jewel. Magnetic damping is em- 

 ployed, the magnets and damping disc being just below the 

 shield. Strong non-magnetic controlling springs giving a full- 

 load torque of 500 millimeter-grams are used. 



The pen consists of a glass reservoir containing a week's sup- 

 ply of ink; into it dips a capillary tube with an iridium tip. The 



