User Manual

System Overview 2-17
board and the value is sent to the monitor processor board. A vent
tube on the b ack of the d iaphragm equalizes for atmospheric
pressure. Three versions of pressure transd ucers are available with
this combo sensor: 0 - 5 PSI (0 - 0.34 Bar), 0 - 15 PSI (0 - 1.03
Bar), and 0 - 30 PSI (0 - 2.07 Bar).
Peak Velocity Sensor
To obtain peak velocity, this sensor sends an ultrasonic signal at a n
angle up through the velo city layers in the onco ming flow. It emits
a wide, omni-di rectional so und wave at a specific freq uency 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 so und wave's frequency from transmissi on to r ecept ion. This
change is used to determine the peak velocity of the flow based on
the Doppler effect.
FLOW
PARTICLES
Peak Combo Sensor peak velocity transducer
The Doppler effect describes the shift in frequency of a sound wave
emitted by a moving object in relation to a sta tionary point. The
moving ob ject s represent particles in the flow, the stationary point is
the vel ocity sensor, and the signal received is the reflection of the
sound wave (emitted by the velocity sensor) off the particles.