AG-AeroCross-00
March 4, 2002
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Figure 2. Linear Averaging Flow Sensor
Inlet Sensitivity:
Inlet sensitivity is a measure of flow sensing accuracy that can be lost to ‘less than ideal’ inlet
conditions. Although SMACNA recommends a minimum of three duct diameters of straight duct in
front of any flow-measuring device, this is often not the case. Obstructions such as plumbing, conduit,
and structural members result in jogs and turns in both rigid and flexible supply ductwork. Real world
conditions require that a good flow sensor is able to read air volume to a +/-5% accuracy, no matter
what the inlet conditions may be. This is critical to guarantee the accuracy of factory calibrated
controls, that would otherwise require a field calibration. It be noted that if excessive inlet sensitivity
results in a reduced flow signal for a given flow volume, the benefit of amplification has been lost.
No controller, regardless of its sophistication, can overcome less than adequate accuracy from a flow
sensor under common field conditions.
The AeroCross
ä
has less inlet sensitivity than any flow probe on the market, with no more than +/-
5% error regardless of inlet condition. While other center-averaging designs are capable of +/-10%
error, linear averaging designs can range from +/-10% to 35% depending upon the exact condition
and angle of approach.
Sound Performance:
The greatest impact of the AeroCross
ä
flow sensor is the effect on sound performance of the terminal
units. The narrower profiles resulted in a reduced pressure drop for the flow sensor. This resulted in
significant sound reductions in the many of the terminals.
The greatest effect is in the ESV product line. Table 1 shows the comparison between the NC values
for the original flow sensor and the new AeroCross
ä
sensor for the ESV.
Total pressure sensing
ports on front
Static pressure sensing ports on
back (not visible in figure)
Pressure reading is taken
at end of sensor
