Hartmann & Braun, Bockenheim- Frankfort o. M. 



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89. Registering Voltmeters and Amperemeters, on the prin- 

 ciple of Kohlrausch's spring galvanometer, which is particularly adapted 

 for this purpose on account of its relatively powerful action, the recti- 

 linear movement of its iron core suspended by a torsionless spring and 

 its perfect damping. With 24 hours and 8 day clock work for the re- 

 gistering drum. 



90. Wattmeter for direct reading. In circular case. External 

 shunt connection as with the voltmeter and amperemeter; the system is 

 similar to No. 19, but arranged vertically and fitted with horizontal axis 

 pivoted between two points. For purrents up to 30 amperes and for 

 voltages up to 150 volts. With extra shunts and additional resistances 

 for several hundred amperes and several thousand volts. 



91. Ohmmeter in circular case for per- 

 manent connection with the circuit, for taking 

 at any time direct readings of the resistances 

 of insulations in ohms. By means of a com- 

 mutator either the positive or the negative pole 

 may be examined with respect to earth con- 

 nection. The instrument can be made for an}' 

 constant voltage. 



92. New Ohmmeter for taking direct 

 readings of resistances. Astatic magnetic system 

 with differential multiplier, so arranged that the 

 indications of the instrument are affected neither 

 by terrestrial magnetism nor by the magnetic 

 momentum of the needle nor by the voltage 

 of the battery. Range from single to hundredfold 

 reading. 



93. New Volt-Coulombmeter. The current which is to be 

 registered deflects the movable system of a wattmeter; a spring supplies 

 the counterforce and is drawn out at short intervals by a very simple 

 clockwork actuated by the current. The travel of the spring is trans- 

 mitted to a registering set of wheels provided with electro-magnetic 

 coupling which becomes disconnected whenever the strength of the current 

 and the tension of the spring are in equilibrium. This play is repeated 

 every minute. Range from single to 200-fold. 



94. Motor-Coulombmeter. By a peculiar arrangement the velo- 

 city of this motor, which is provided with electrical damping, is rendered 

 proportional to the current. By a special device absolutely certain starting 

 is ensured even with the weakest current. An automatic switch for the 



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