Nil. lil 444. 



String Galvanometers. Shunts. 



893 



61 444. 1 



Shunts for Mirror Galvanometers. 



8. d. 



Galvanometer Shunts, Figure, for varying the sensitivity : 



For 1 Galvanometer with 

 a Kesistance 



61,438. 

 61,439. 

 61,441. 



to 



1 Ohm 

 100 Ohms 



100 



1000 



Eeduction of Maximum 

 Sensitivity to 



0.1 0.01 2. 0.0 



, 

 0.1 0.01 0.001 12. 10. 



0.1 0.01 0.001 0.0001 . 3. 0.0 



Shunt Resistances Nos. 61,438 61,441 have a short circuit plug. The resistance coils are wound 

 on copper and connected up in such manner that 1 / 9 , 1 / 99 , 1 / 99e etc. of its resistance is connected in 

 parallel with the galvanometer. These shunts are therefore chiefly suitable for Moving Needle Galvano- 

 meters, as they do not give constant damping with Moving Coil Galvanometers. When ordering, the 

 resistance of galvanometer should be quoted. 



61,394. Universal Shunt connected up according to Ayrton's method, Figure 61,394, 

 p. 888, for Needle Galvanometers and Moving Coil Galvanometers; damping ratio appro x. 

 constant; suitable for all galvanometer resistances up to 100 ohms; total resistance 

 10,000 ohms; stages, 1, 1 / 10 , Vioo> Viooo? Vioooo! constructed of manganin 



3. 0. 



61.442. --idem, total resistance 100000 ohms, for Galvanometers up to 1000 ohms 

 resistance 



61.443. Power Shunt after Prof. Kommerell, German Design, Figures A and B (Ztschr. 

 f. d. phys. 11. chem. U. 22, 1909, p. 13) 



The object of the power shunt is to enable sensitive Mirror Galvanometers to be used not only 

 for their original purposes demonstrating and measuring very small currents but also for measuring 

 currents to about 15 amperes. Fig. 61,443 B shows the connections of the apparatus. Complete 

 description forwarded if desired. 



Reading Devices for Mirrors Instruments. 



The angle of rotation of Mirror Instruments is measured either in a subjective 

 manner, in accordance with Poggendorff's suggestion, with the aid of a Telescqpe and 

 Scale, or, in an objective manner, by projecting the filament of an electric, glow lamp 

 or the shadow-image given by a wire stretched in front of a brilliantly lighted aperture, 

 on to a scale. In the first case the rotating mirror must be a Plane Mirror; in the second 

 case either a Plane .Mirror with projection lens in front, or a Concave Mirror, is used. 



61.444. Simple Reading Telescope with paper scale, Figure, for" schools and exercises , 



The Telescope is fitted with a 24 mm diameter objective and cross wires; it has a vertical 

 adjustment and can rotate about the horizontal and vertical axis. 



4. 10.0 



9. 0.0 



5.0 



Cl. 239.1. 



