Analysis of the 



THE EFFECT OF THE ANEMOMETER ARMS 



Deviations from the general law are shown by the dotted lines (Fig. 5) and represent the 

 effect of the anemometer arms. For the smaller cup sizes the arms were of relatively greater thick- 

 ness and presented a larger resistance (cf. also Patterson 1 ) so that h will increase with a non- 

 dimensional parameter involving the arm thickness (<5 = diam. for cylindrical arms) and of the 



Fig. 5 



form b/d{D/d— 1). This simple parameter is chosen as the ratio of the area of the arms exposed 

 to the wind, 8(D — d), to the area of the cup face Kd 2 . In Fig. 6 the deviation Ah of the value of h 

 from the general law is shown as a function of S/d(D/d— 1) where Ah is the effect of the anemom- 

 eter arms on the factor /;. 



