BAIRD &. TATLOCK (LONDON) LTD. 



The Stem. The stem which is heated contains two alloys joined together at the sensitive end. The 

 heating of the junction generates an electric current which actuates the indicator or recorder. The more the 





Fig. 2. Practical Pyrometer, Portable Outfit. 



About one-quarter full size. 

 The full length of the Stem is not shown, the tip being cut off for convenience. 



junction is heated, the higher is the current. The Hoskins Patent Alloys enable this current to be large, thus 

 making the whole apparatus robust. 



The internal construction of the stem varies with the maximum temperature it has to withstand, but in 

 all the standard types for shop use the construction embodies a stout steel tube f in. diameter. In the type 

 for use up to 600 C. (nooF.) the steel tube is pierced to allow the heat to reach the sensitive junction, thus 

 securing very rapid action. Up to 1050 C. (1900 F.) the protection is heavier, while for temperatures above 

 this a special refractory protection is used inside the steel tube, so that the burning away of the tube does not 

 put an end to the use of the stem. It should be noted that in none of the stems is there any platinum wire ; 

 nor porcelain, quartz, or other fragile material. 



Cold End Extension. For reasons which are explained on following page, it is desirable that the point 

 where the alloys of the stem join the cable should be at a steady low temperature. In fixed installations this 

 would often necessitate a very long stem. To avoid this we supply a cold end extension with fixed outfits, 

 composed of similar alloys to the stem. This extension, which is twenty-four inches long, adds to the effective 

 length of the stem by that amount, but does not have to be replaced in the case of renewals. 





Fig. 3. Scale of Indicators. 



About full size. 



-CROSS STREET HATTOTST GARDETST, E-C 



980 



