534 Wright — Telemeter with Micrometer Screw Adjustment 

 L 3 -Obj. CD 



LxV: I)A 



(l) 



Let distance of object I^-Obj.^y and movement of micro- 

 meter screw AD=x, then 



y_ 



a 



y = 



a 

 2.x 

 a 2 

 2x 



or 



(2)' 



To find the relative accuracy of the instrument for different 



Fig. 3. 



vU/ 



\/ 



M 



C7-o 



^m 



m 



N/ 



o 



distances y for a given small increment of x, equation (3) may 

 be differentiated. 



dy 



a? dx 



2~ c? 



(3) 



Since absolute values only are considered and not the fact that 

 x and y are counted in opposite directions, the negative sign of 

 equation (3) may be disregarded. On substituting the value 

 of x from (2) in this equation, we obtain 



dx (4) 



U « 2 



which states that the sensitiveness of the instrument decreases 

 with the square of the distance and increases with the square 

 of its length. . . 



In the trial telemeter of fig. 1, the distance L x L 2 ~a is 

 93-5 cm or about 1 meter. The micrometer screw reads to 



