ABSTRACT
This chapter describes most of the instruments with the exception of instruments based on the quantification of other variables, such as pressure. It also describes the various field instrumentation used for measuring water velocity at a point in the field. Flow velocity measurements are an essential component of experimental hydraulics and hydraulic model validation. The chapter presents the background of Acoustic Doppler Velocimeters, Ultrasonic Velocity Profilers and Acoustic Doppler Velocity Profilers. It also presents the system configurations that are most often used in geophysical and laboratory flow studies: monostatic instruments and multistatic instruments. Multistatic acoustic backscattering instruments that have been developed and are commercialized as point measurement instruments measuring in a single gate volume, are called acoustic doppler velocimeters (ADVs). There are several ADVs on the market with different configurations: three-receiver configuration and four-receiver configuration. Velocity from the Doppler frequency does not require calibration since Acoustic Backscattering Instruments remain calibrated throughout their lifetime.
