An Area-Velocity Flow Meter continuously measures both Level and Velocity to calculate flow volume in an open channel or pipe.

The ultrasonic sensor is installed at the bottom of a pipe or channel. To measure water level the sensor transmits ultrasonic pulses that travel through the water and reflect off the liquid surface. The instrument precisely measures the time it takes for echoes to return to the sensor. Based on the speed of sound in water, the level is measured with accuracy of ±0.25%.

Flow velocity is measured with an ultrasonic Doppler signal continuously injected into the water. This high frequency sound (640 KHz) is reflected back to the sensor from particles or bubbles suspended in the liquid. If the fluid is in motion, the echoes return at an altered frequency proportionate to flow velocity. With this technique the instrument measures flow velocity with accuracy of ±2%.

Greyline Area-Velocity Flow Meters work in partially full and surcharged pipes, rectangular, trapezoid and egg-shaped channels.

Greyline Area-Velocity models and specifications:

	For semi-permanent installations... Check out the AVFM 5.0 Area-Velocity Flow Meter for applications in partially filled pipes and channels. It displays and transmits flow, level and velocity with three 4-20mA outputs.
	Portable data logging model... Check out the portable, battery-powered Stingray Level-Velocity Logger for flow surveys and I&I studies. It runs for up to 4 years on a set of standard D-Cell Alkaline batteries.