ON A NEW VELOCITY RECORDER. 281 



On a New VELOCITY RECORDER and its Application to 



Anemometry and other Purposes. 



By J. Alfred Griffiths, b.Sc, wh.Sch., M.i.Mech.E. 



[With Plate XLL] 



[Bead before the Royal Society of N. S. Wales, November 7, 1894.~\ 



(Abridged for Publication.) 

 In recording a continuously growing function on a travelling 

 band of paper by a pen moving at right angles to the paper, the 

 inconvenience arises when the experiment is continued for extended 

 periods, of the pen travelling far beyond the limits of any reason- 

 ably sized sheet. This has hitherto been obviated, either, (1) by 

 limiting the experiment or record to the extent of the sheets of 

 paper which are changed frequently ; (2) by recording some 

 derived function of more limited range or periodic character, from 

 which the original functions may be deduced ; or (3) by various 

 devices for causing the pen to periodically return to zero and 

 commence a fresh portion of record on a band of paper of limited 

 width. 



Many devices* have been used in previous recording meters, and 

 (notably for anemometers) it has been the practice for the rotating 

 wind-vane to move the pen by continuous motion which is inter- 

 rupted at the end of fixed periods of space when the pen returns to 

 the zero line, producing a saw-tooth diagram, each tooth of 

 which indicates the passage of so many miles of wind. When 

 the space interval is made sufficiently small with respect to the 

 extent of speed variation, the pitch of adjoining teeth is fairly 

 constant over short intervals, and the average speed may be 

 measured by counting the number of teeth between each time 

 vertical. 



* See Prof. H. S.H. Shaw, on " Measurement of Velocity "— Proc. Inst. 

 C.E., Vol. lxix., page 369. 



Tylor on "Recording Water Meters,"— Proc. Inst. M. E., 1886. 



