Part Two
Figure 7: Pressure sensor door slid open.
Sensor span
NOTE: Always take a sensor zero prior to adjusting the sensor span. A smoke
test and a comparison measurement by an air velocity meter are
required to calibrate the pressure sensor. The air velocity meter only
gives a velocity reading, so a smoke test must be performed to
determine pressure direction.
WARNING: The span can only be adjusted in the same pressure direction.
Adjusting span cannot cross zero pressure. Example: If unit
displays +0.0001 and actual pressure is -0.0001 do not make any
adjustments. Manually change the air balance, close or open
dampers, or open door slightly to get both unit and actual pressure
to read in same direction (both reads positive or negative). This
problem can only occur at very low pressures so slightly changing
the balance should eliminate the problem.
Perform a smoke test to determine pressure direction.
Select SENSOR SPAN item (2SENSOR SPAN item if second sensor).
Position the thermal air velocity meter in door opening to obtain velocity reading.
Press / keys until pressure direction (±) and sensor span match thermal air
velocity meter, and smoke test.
Press SELECT key to save sensor span.
Exit menu, calibration is complete.
Flow station pressure transducer zero (Premium units only)
Disconnect tubing between pressure transducer and flow station.
Enter calibration menu. Access code is required.
Select FLOW ZERO to take flow zero.
Press SELECT key. Flow zero procedure, which takes 10 seconds, is automatic.
Press SELECT key to save data.
Connect tubing between pressure transducer and flow station.
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