Swoffer Instruments 2200-3000 Instruction Manual

MODEL 2200-3000 RETROFIT OPEN STREAM CURRENT METER / PAGE 1 of 7
Supplement to Model 3000 Instruction Manual
DESCRIPTION AND INSTRUCTIONS FOR INSTALLATION OF METER HARDWARE
Although titled both a "current meter and a flowmeter", the Model 2200-3000 is actually a retrofit sensing and
readout device that is designed to be used with existing Price Type AA and Pygmy current meters. These
meters, developed by the U.S. Geological Survey, have been in use for over ninety years yielding reasonably
accurate current velocity data by timed counting of "bucket wheel" revolutions. Meter construction is closely
controlled and "standard rating tables" of velocity as a function of revolutions and time are published by the
USGS. The original method of counting bucket wheel revolutions is by counting "clicks" generated in a
headset by the bucketwheel-driven contactor. The interval over which the clicks are counted is determined by
use of a stop watch. The stream velocity is then taken from the rating tables provided by the manufacturers
and the USGS. Users not familiar with the Price Meters are referred to the WATER MEASUREMENT
MANUAL and other publications prepared by the USGS.
Price Type Meters have been mechanically reliable for many years; however accuracy has been a function of
careful maintenance and adjustment of the delicate "cats-whisker" contactors and proper lubrication of bearings
and penta gears. Even with regular maintenance and the proper adjustments and operating procedures the Price
Meters are not considered accurate below 0.2 feet per second. The inherent levels of friction caused by the
cats-whisker contactors and the worm gears (AA Meter) inhibit bucket wheel turning at these velocities.
The optic sensor for the Model 2200-3000 is designed to eliminate as much friction as possible. The output
signal of the sensor is produced by a non-contacting PHOTO-FIBER-OPTIC device that completely replaces
the contact chamber assembly (AA Meter) and the cats-whisker contactor (Pygmy meter). Rotational friction
is brought to minimum and accurate readings down to and below 0.1 foot per second are attainable under ideal
conditions.
Once the sensor adapter parts are installed on the AA and Pygmy meters the 2200-A, photo-optic sensor can
easily be placed on either meter as desired. The 3000 Indicator will then provide stream velocity readings and
flow rates in any of several modes. This manual describes the installation of the optical retrofit sensor and
adapters to AA and Pygmy type meters.
Fig. 1