ADS Environmental Services FlowShark QR 775002 A4 - Manual (Page 32)

System Overview 2-19
reading the difference in pressures. Temperature compensation
occurs through a temperature sensor located within the pressure
depth sensor housing.
Doppler Velocity Sensor
The Doppler velocity sensor (ADS p/n 103260A-35) mounts at the
bottom of the pipe. It emits a wide, omnidirectional sound wave at a
specific frequency upward into the flow. The sound wave bounces
off particles in the flow and returns to the sensor. The velocity
sensor measures the change in the sound wave's frequency from
transmission to reception. This change is used to determine the
velocity of the flow based on the Doppler effect.
The Doppler effect describes the shift in frequency of a sound wave
emitted by a moving object in relation to a stationary point. In this
case, the moving objects are particles in the flow, the stationary
point is the velocity sensor, and the received signal is the reflection
of the sound wave (emitted by the velocity sensor) off the particles.
Doppler velocity sensor sending signals reflecting off particles in the flow