PCWA-L 467.pdf - PCWA Middle Fork American River Project ...

28 MEASUREMENT OF STAGE AND DISCHARGE
large to be accommodated by the adjustable index. A 10-;n (0.25 m)diameter
copper float and a 2-lb (0.9 kg) lead counterweight are normally
used. The float-type gage is used chiefly in stilling weHs as an
inside reference or auxiliary gage.
ELECTRIC-TAPE GAGE
The electric-tape gage consists of a steel tape graduated in feet and
hundredths of a foot, to which is fastened a cylindrical weight, a reel
in a frame for the tape, a 414-volt battery, and a voltmeter. (See fig.
12'> One terminal of the battery is attached to a ground connection,
and the other to one terminal ofthe voltmeter. Tbe other terminal of
the voltmeter is connected through the frame, reel, and tape, to the
weight. The weight is lowered until it contacts the water surface; this
contact completes the electric circuit and produces a signal on the
voltmeter. With the weight held in the position of first contact, the
tape reading is observed at the index provided on the reel mounting.
The electric-tape gage is used as an inside reference gage and occasionaHy
as an outside gage. If oil is floating on the water surface, the
gage will give the gage height of the interface, because oil is a dielectric.
In some electric-tape gages a liRht or audible signal is substituted
for the voltmeter.
FIGURE 10.-Type A wire-weight gage.