No. 01832. 



Standard Resistance. Petroleum Baths. 



921 



61 932 A. 1:8. 



61 932 B. 1:3. 



one massive binding screw for leading in the current and each a second for the potential lead. In the case of 

 the resistances with special shunt terminals the potential lead is fixed to these. The petroleum bath contains 

 a cooling vessel for water circulation and an efficient turbine for circulating the petroleum. The turbine 

 lias a cord drive, being actuated by a small electric motor or a water motor. 



61,928. Petroleum Bath for 4 Eesistances, with one turbine, 5 short bars with terminals and 

 mercury cups for series connection and 2 long bars for parallel connection of the re- 

 sistances, Figure 



s. d. 



61.929. - - i d e in, without the two paralleling rails 



61.930. - - i d e in, for 5 resistances, with turbine, 6 short and 2 long copper bars 



61.931. - - i d e in, without the 2 copper paralleling bars 



7. 0.0 



6. 0.0 

 9. 0.0 



7. 15. 



61,932. Petroleum Bath, Figs. A and B, own new pattern, for comparing single resistances 

 and two resistances in series and for determining temperature coefficients; with heating 

 and cooling arrangements, Fig. B ; can also be used as it stands for the Thomson 

 method of connecting 



Standard Resistances can be compared both by the Wheatstone and the Thomson method with 

 t lie aid of the shunting resistances Xos. 61,924 61,926. The heating is done by a glow lamp and the 

 cooling by a water jacket and stirring turbine. 



Resistances and Bridges for Scientific and Technical 



Purposes. 



Precision Rheostats of Manganin Wire, impregnated with shellac and heated for 10 hours 

 to 140 C. before calibration. The ends of the resistance coils are silver soldered flush 

 on to copper pieces and the latter can be soldered with tin to the bolts which are used 

 us conductors. The plugs have ebonite grips. 



The plug blocks are provided with special plug-holes for in selling wire connected 

 terminals so as to be able to use each resistance coil singly. The resistance coils to 

 5 ohms are wound bifilar (non-inductive), those above 5 ohms in accordance with 

 Chapron's method (non-inductive and anti-capacity). Each resistance box has openings 

 which may be closed, for steadying the temperature, and opening for taking a thermo- 

 meter. The error of calibration of the precision resistances is within one part in one 

 thousand. The resistances are calibrated in International Ohms. 



The following is the permissible load : 



Resistance in Ohms 0.1 0.4 1 4 

 Permissible Current, Amps. 1 0.4 



100400 

 0.04 



10004000 

 0.015 



10 00040 000 

 0.003 



16. 0. 



Cl. 4968, 4972. 



