CURRENT METERS 17 



\\li.-n the acousiK i nil mil ing device is used, the contact 

 chamber (lOb) is closed with a cap i 1 1 In iitt.,1 with a metal 

 hum (49), and, in place of the com .. t -j.i .!./ - I 1 i and plug 

 (16), there is a small hammer (50) which is caused by the pin* 

 ..U til*- M.|. <*t id. /. ..i uli. . 1 i 13a) to strike the drum at each 

 truth iv\,.luhon ..t iln- . tips. In order to keep the wat r : 

 <li M< lining the sound by rising into the contact chamber (lOb), 

 n i raised al-m ! MI above the yoke (la) by inserting 



the tulie (59) and lengthening tin- upper part ..i the shaft (4a). 

 The acoiMie in. i. i is always supported on a rod (51 ) attached 

 t" thr contact chaml 



2. THE TAIL. The tail is used when the meter is suspended 

 by a cable, or on a sliding hanger rod. It balances the head, 

 and also keeps the axis of the meter parallel to tin .Im-.-ti,,,, of 

 tin 'Mir. ni. It consists of a stem (17 \%lm-li in held In a 

 didini: fit into a socket in the M.-III of the yoke, in whieh it is 

 clamped by a set-screw. On this stem there are two vanes ( 18 

 and 19) Ml .n right angles. One of the vanes is rigidly attached 

 I-- tin M< m; the other fits into grooves on the first and may be 

 }. nlled out readiK when the key (20) that holds it in place is 

 turned. On one of the vanes there is a slot carrying a weight 

 (21) that can be adjusted to balance the meter. 



3. I Hi HANGER AND WEIGHTS. When suspended by a 

 eal.le. the meter is hung by a screw-bolt (22) on a steel stem 

 (23) that passes through a slot in the stem of the yoke. The -lot 

 in the >tem of the yoke is wide enough to allow the meter to 



4 freely in a vertical plane, and the bolt passes through the 

 ! a little above the nt. r of ura\ily of the meter, so that 

 the latter will readily adjust it-elf t< a horizontal position. In 

 the upper end of the hanger there i> a hole |,, r alt aehing the 

 -u-pended cable, and at int. -r\als along the Mem then- arc other 

 holes by \\hieh the meter and lead weights may be hung. The 

 \M -ii:ht- (24) are of torpedo shape, a design which offers the 

 least resistance to the eurn-nt. -and are made in two sixes 

 weighing, respectively, 10 and 15 pounds. They are atta 

 to the stem by a screw bolt. The order in whieh the weights 

 and meter are plaeed on the >tem. de|>ends on the conditions 

 under whieh the measurements are to be made. 



When the meter is used on a rod, the hanger, the weights, 

 and sometimes the tail are dispensed with. 



