A BRA UN TUBE HYSTERESIGRAPH 293 



1. The Integrator. 



The integrator unit contains two banks of paper condensers of 

 100 mf. each, variable in steps of 1 mf., 3 mf., 6 mf., and 9 steps of 

 10 mf. The two resistances are each variable by factors of about 

 two from 12,000 ohms to 1,000,000 ohms. These combinations are 

 thought to cover any requirements that are likely to arise. 



2. The Amplifier. 



Four stages of Western Electric 102-D tubes on each side, resistance- 

 capacity coupled, make up the amplifier. The time constant of each 

 coupling unit (stopping condenser and grid leak) is 8 seconds, which 

 is sufficient for frequencies down to 10 p.p.s. or less. The amplifier 

 is suitably shielded against electromagnetic, mechanical and acoustic 

 shocks. 



3. The Oscillograph. 



A box contains the cathode ray oscillograph tube ^ and its controls, 

 except the batteries. The coils // are mounted on a hard rubber 

 holder which can be clamped securely to the tube. A camera attach- 

 ment contains a Dallmeyer F. 1.9 lens with which photographs of the 

 pattern can be made on plates or film pack. 



The oscillograph tube is connected to the amplifier unsymmetrically 

 since one side of the amplifier leads to the common deflector plates 

 and the batteries of the oscillograph tube, the other side only to a 

 deflector plate. The oscillograph and its batteries must, therefore, 

 be so placed that the conductance and capacity to ground and to the 

 rest of the apparatus are small. When this is done no distortion 

 results from the lack of symmetry. 



4. The Calibration Set 



The calibration box contains the apparatus for applying a small 

 sinusoidal voltage of known amplitude to the amplifier and oscillo- 

 graph. The set takes current from the same source that supplies 

 the magnetizing current. A low-pass filter admits only current of 

 the fundamental frequency, and a thermocouple provides for measuring 

 the output current of the filter. This current passes through a 

 potentiometer from which the calibrating voltage is applied to the 

 amplifier. The potentiometer is variable in several steps, each 

 reducing the current amplitude by a factor of about two. 



3 Western Electric 224-B tube. J. B. Johnson, J. 0. S. A. and R. S. I., 4, p. 701, 

 1922. 



