LONG ARM 



Figure F-8. Culbertson Slide Rule. 



Figure F-9. Portion of A-Sheet taken from chapter B. 



NOTE : The average T„ always must be deter- 

 mined before the unprotected thermometer can 

 be corrected. 



Step 5. To calculate Cu, set the arms on the 

 average T,. and the t^, on the linear temperature 

 scale surrounding the striped graph. Set the 

 long arm on the larger value and the short arm 

 on the smaller value, e.g., average T^ (15.12°) 

 and tu (corrected) (18.5°) for unprotected ther- 

 mometer number 196-64 (fig. F-12). 



Step 6. Move the arms until the short arm is 

 atO° (fig. F-13). 



Step 7. Under 159.65° (Vo + T'u) (139.6 + 

 20.05) on the long arm, read .09° (C) on spiral 



stripes. If T'u -\- Vo is off scale on the long arm, 

 take half the value and double C. 



Step 8. To obtain Cu, move the long arm to the 

 left by the amount of C' on the linear scale (fig. 

 F-14). 



Step 9. Under 159.65° (T'u + Vo) on the long 

 arm, read the correction (Cu) .09°. If Tw is 

 less than tu, the correction Cu will be negative. 



Step 10. Enter Cu (-.09°) in CJC^ column 

 of the A-Sheet. 



Footnote: When the word "set" Is used, the arms are set 

 Independently, the long arm always being set first. When the 

 word "move" is used, both arm^ are moved simultaneously, 

 keeping a constant angle between them by moving the long 

 arm. 



F-11 



