CURRENT METERS 21 



SI 1 KCTINC THE PROPER TYPE OF CURRENT METER 



Ih. .-\priirnee of many years ha* shown that only two 

 p.iii.-m- ..I ih. <.mle\ in.* needed to adrquat'-lx meet 



ih. i ni- .'I j.i.., h. .illx all enquirer* engaged in meaur- 



the tlo of water, namely the Acoustic type. No. 616, and 

 ill. I I., in. type, represented by No*. 617, 621 and 623. 

 According. tli- l-trge model formerlx lifted as No. 600, and 



the -in. ill. T p.m. in-. No. 618, have been discount 

 No. 617 an have been -i.md.irdi/.-d h\ ..pupping 



ih* in \Mth the Covert \<>k . as described on page 24, thus mak- 

 ing them corre*|< No. 623 * \. pt th.it .nl\ one commuta- 



tor box is supplied, single count \%ith No. 617, and penta count 

 No. 621, whereas No. 62 > In- Uth itures. 



Thus, if Meter No. 617 or No. 621 is selected and the 



deer tm.1- ih.it both commutator boxes are required. h- 

 ran pin. ha-e the . \tra single count or penta count head and i!n-n 

 have Meter No. 62 



Tin- M-lrrtinn {' a nn'tT -hmiM he mal.- aftiT r,,n-i.!.Tati..n 

 has been gi\-n ! th- following factors: 



i I ) The purpose lor \\hi.-h th- iii-tniim-nt is to be used. 

 'Hi.- m.imi.-i in \\hi.h il i- supported. 



(3) The amount of weight to be used. 



(4) The frequency of the resolutions to be indicated. 



\\ li.-n it is possible for tin r to approach the stream 



closely, and to hold the mrtrr in position |,\ nn-an- of it- -u-p.-n- 

 sion rod, eJ|--iall\ in .-hanneU of -inall depth, the \eouMie 



Current Meter No. 6)6 is very useful. Tlii- meter indicate* 

 each tenth rexolnii.m. See page 22. 



No. 616, the Acousti. ( unrnt M.-t.-r. is so called because 



ih. revolutions of th I.IM k.-t \\herl are imlieatetl h\ the sound 

 of a hamm< i -triking atiainst a diaphragm, one Now for every 



revolution-. Th- imlieatint: meehani-m is coinpleteU 

 em -losed and thoroughly protect etl from injurx. \\hen in u-e 

 the ineirr i- held 1.x a de,-\,-.j..mted wading nnl. whieh -erews 

 int> ih.- 1 1. mi.- .in.l in e..nne. ti.n \\ith a rubber tube and ear 



' attached to it. forms a passage through which the sound 



