USGS TYPE AA MODEL 6200
The USGS Type AA
current meter is commonly known as the Price-type current meter. This
current meter is suspended in the water using a cable with sounding
weight or wading rod (taking the tail section off) and will accurately
measure streamflow velocities from 0.1 to 25 feet per second (0.025 to
7.6 meters per second). The main features of this meter are the
uniquely designed bucket wheel shaft bearings and the two post contact
chamber. The bucket wheel has six conical shaped cups, is five inches
(12.7 cm) in diameter and rotates on a vertical axis inside the yoke.
The tungsten carbide bearings for the bucket wheel shaft are located
in deeply recessed inverted cups. When the meter is in use, these cups
become air chambers and the entrapped air effectively excludes water
and silt from the bearing surfaces giving extremely low starting
velocities and minimal friction in the bearings.
The contact chamber
houses a penta gear and two binding posts, each having a fine platinum
alloy contact wire. One wire makes contact with the bucket wheel shaft
once during every revolution; the other is used when fast velocities
are encountered, and makes contact with the penta gear once during
every five revolutions of the bucket wheel.
Each current meter is
provided with a U.S. Geological Survey approved standard rating table
to convert bucket revolutions to stream velocity in either English
units (feet per second) or metric units (meters per second), spare
parts, instrument oil, cleaning cloth, screwdriver and an instrument
case with a water tight o-ring seal that floats if dropped in the
water and provides proper protection of the meter during
transportation and storage.
The meter is made from
brass and stainless steel and all exposed surfaces are chrome plated
for corrosion-free service. The standard Type AA was designed for use
with all of the counters as well as the AquaCalc 5000 Digital Flow
Computer. No conversion kits or replacement contact chambers are
necessary to use the latest digital technology with this meter.
