164 



Hartmann & Bratm, Bockenheim- Frankfort o. M. 



17. Silver Voltameter and Copper Voltameter for calibrating 

 industrial galvanometers, the former for a current of 0.25 amp., the 

 latter for currents up to 5 amp. Also Kohlrausch's Water Voltameter. 



Analytical balance for determining the weight of silver or copper 

 deposited by the voltameters. 



18. Direct Reading Aperiodical Torsion Galvanometer, 

 ranging from 1 to 100-fold. Various models 



for current strengths within the limits of 1 milliampere 

 and 10 amp.; 



for E. M. F.'s within the limits of 0.01 and 1000 volts; 

 also combined in one instrument with shunts and addi- 

 tional resistances for 0.1 to 18 amp. and 0.1 to 180 volts. 

 These torsion galvanometers are constructed on the lines of Deprez's 

 galvanometer, but embody a series of very important improvements, the main 

 object of which are to maintain a constant homogeneous magnetic field, to shield 

 the instrument from the influence of the extraneous circuit and to add to the 

 portability of the instrument. 



19. 



19. Torsion Electro dynamometer for continuous and alternating 

 currents. Various models, for use 



as amperemeter for currents up to 50 amp., 

 as voltmeter for E. M. F.'s up to 180 volts, 

 as wattmeter for energy up to 120 voltamp. 



The indications of these instruments are based upon the movements 

 produced by a solenoid acting upon a double rotating solenoid with similar outer 

 and inner poles: NS SN. 



The convenience of direct reading by means of a scale having nearly 

 proportional divisions, the range from 1 to 100 -fold measurement, the damping 

 arrangement, in particular however the absence of magnets or iron render these 

 instruments eminently suitable for calibrating other instruments. 



