AG-AeroCross-00
March 4, 2002
2
Introduction
Accuracy of airflow control is critical to terminal unit performance, because of its impact on many
important aspects ranging from acoustics to occupant comfort. The key to accurate flow control from
a terminal unit is well-designed and repeatable airflow sensor. While there have been many
improvements to both flow transducers and controller software/algorithms from the HVAC controls
industry, all are dependent on an accurate flow signal from a flow sensor. A flow sensor that can
measure accurately regardless of inlet conditions simplifies and takes much of the guesswork out of
the balancing and commissioning process.
The Titus multi-point center averaging flow sensor is the number one sensor on the market because it
is accurate regardless of inlet conditions. A flow sensor should provide flow signal amplification and
immunity from poor inlet conditions, while keeping pressure drop and sound levels to a minimum. In
addition, a flow sensor should have a high degree of repeatability and sturdy construction.
The original flow sensor design required a trade-off between amplification (accuracy) and pressure
drop (sound), resulting in a very accurate sensor that was occasionally louder than the competitions’
sensors. Using Computational Fluid Dynamics (CFD) software, we were able to design a new flow
sensor that maximized amplification and minimized pressure drop.
We are happy to introduce the AeroCrossäflow sensor.
Description
The flow sensor is the most important component of a VAV terminal. The flow sensor measures the
total and static pressure in a terminal so that a controller can calculate the cfm through the unit. If the
flow sensor does not provide accurate information to the controller, the controller cannot determine
actual cfm, and therefore cannot maintain comfort in the space.
The AeroCrossäis a multi-point center averaging flow sensor. The new sensor has a narrower profile
than the original sensor. To visibly differentiate the new sensor, the AeroCrossäwill be blue. The
flow label on the terminal will also be blue to allow for easy identification from the outside of the
unit. Like the original Titus flow sensor, the AeroCrossäis injection molded out of a high impact
plastic material.
Performance
Amplification:
Amplification is the ability of a flow sensor to produce a signal greater than the velocity pressure.
Pitot tubes read true velocity pressure, which requires 4005 FPM to produce a 1” wg signal. Velocity
pressure is the difference between total pressure (taken from the tip of the probe) and static pressure
taken from the side of the probe). Amplified flow sensors improve upon this signal by taking the
difference between total pressure (from the front of the probe) and a reduced static pressure (from the
rear of the probe). Amplification is critical to accurate control of minimum flow rates. While many
