Mounted above the water surface the Teledyne Isco LaserFlow™ measures point velocity at up to fifteen different points at three different depths below the water’s surface using a laser diode that transmits and receives a focused laser light beam. Velocity is calculated from the Doppler-shifted signal frequency that is returned. This evaluation test was conducted by Environment Agency (Sept. 2014).
Main objectives of the evaluation were to:
- Evaluate performance of the LaserFlow™ meter against an existing flow gauge.
- Assess the potential for non-contact LaserFlow™ technology to be used in the Environment Agency flow monitoring network.
- Determine the installation requirements and operating range of the instrument.
A field test was undertaken to evaluate the performance of the Isco LaserFlow™ in open channel river systems. The accuracy of the flow data has been assessed to determine the potential of using a laser velocimeter in the Environment Agency’s hydrometric network. This report details some results of the evaluation process, testing the instrument under ideal flow measurement conditions. Results show the LaserFlow™ measures discharge to within the measurement uncertainty of the reference flows. Test results indicate the unit would be suitable at locations similar to bed and wall-mounted hydro-acoustics. Its ability to measure velocity in weedy channels also needs investigation. The Laser is a class 3R beam (same classification as a laser pointer in the USA), so installation at sites where the instrument can be accessed by the public should be avoided.
Field Tests: This test report details the performance of the TIENet™ 360 LaserFlow™ compared against a Sarasota 2000 ultrasonic time-of-flight flow meter and lowTracker spot gaugings. The test site was at the Environment Agency’s stream flow gauging station on the River Leen in Nottingham. The measuring reach has a long straight approach with a symmetrical velocity profile, which limits other sources of error such as skew flow and eddying.
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