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Thermal Dispersion Airflow Measurement Technology
Thermal dispersion technology relates the velocity of the air
to the power and rise in temperature of a heated element in a
moving airstream. A precise bead-in glass thermistor probes
the airflow rate and air temperature. Multiple sensing points are
used to produce an average velocity for true volumetric airflow
(CFM/LPS). Each individual sensor node is calibrated to NIST
traceable airflow standards at 16 points, resulting in a accuracy
of 2% of the reading.
Figure 45: Bead-in-Glass Thermistor
Figure 46: Bead-in-Glass Thermistor Probe
Connecting to MicroTech III Controllers
Wiring
1 .
Connect analog control wires from the MicroTech III
Controller to the outdoor air monitor controller.
a .
MicroTech III controller (X1 on the MCB or X11
on the EXP_D) to the controller's analog output
terminal 1 .
b .
MicroTech III controller (M on the MCB or M on the
EXP_D) to the controller's analog output terminal
COM.
2 .
Power Wires (24 VAC) to the outdoor air monitor
controller.
a .
24VAC from the unit control panel to the controller
terminals L1 and L2.
Outdoor Air Monitor Controller Settings
1 .
Set Controller SW1 switch to Vdc.
2 .
Set power switch to ON.
Outdoor Air Monitor Controller Configuration/
Set Up
Appendix, Figure 102 on page 129
Controller keypad)
1 .
Set LCD1 U/M to "CFM"
2 .
Set AR1 (see
3 .
Set OUT1 U/M =CFM
4 .
Set OUT1 =0–10V
5 .
)
Table 24: Settings by Cabinet Size
Unit size
Economizer and
0–100%
0–30%
Area sq .ft . (AR1)
Full scale output
CFM (FS1)
Small cabinet
7 .3
4 .75
10,000
Medium cabinet
10 .0
9 .5
10,000
Large cabinet
14 .5
10 .0
10,000
Thermistor material
designed for self-heat
applications is fused
to dumet wire leads
Dumet wire ensures
hermetically sealed
glass encapsulation
Kynar
®
coated wires are
welded to dumet leads
Thermistor aging
process ensures
long term stability
Waterproof potting
compound protects
assembly from the
environment
Zero Power Thermistor
Approaching
Airstream
Self-heated Thermistor
Heat transferred to
the airstream is
proportional to the
airflow rate
IM 1058-8 • MAVERICK II ROOFTOP SYSTEMS
48
www.DaikinApplied.com
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