Data Aire dap4 User Manual page 40

MENU J – FACTORY SETTINGS (factory level) continued
Note: The Fan Air Flow screen is only displayed when CW or DX fan mode is set
to modulate to maintain Air Flow.
The dap4 uses a proportional integral derivative algorithm (PID) to maintain air
flow. The description of the settings offered below is only a guide. The difference
between the set point and the actual measured air flow is called the error.
Status: This is the display of the current airflow in cubic feet per minute.
Setpoint: This is the airflow set point in cubic feet per minute.
Integration Time: Used to slowly shift the fan speed level as a result of an error
between set point and t h e measured a i r f lo w. The h ighe r Integral time
setting, the slower the f an speed level will be shifted. If the Integral time is set
too low the f a n sp e e d level could ch a n g e quickly, causing oscillation. If
Integral time setting is too long, fan speed may become sluggish to change.
A setting of 0s (default) puts the algorithm in a proportional only mode. Range of
adjustment is 0 to 999s.
Band Per Fan: This setting is effectively the "sensitivity" of the algorithm. The
smaller the band, the more the algorithm will try to correct the error. If the band
setting is too low, the system will oscillate by being over-responsive. If the band
setting is too high, fan speed may lack responsiveness. Ideally, the band
setting should be as low as possible without causing oscillation. Range of
adjustment is 0 to 32767cfm with a default of 666cfm.
Derivative Time: Causes a sudden change in fan speed to correct the error as a
result of a quick change in measured air flow. Typically, the derivative setting is
about a sixth of the Integral time setting.
Current Demand: This indicates what percentage of the maximum speed that fan
is currently being driven.
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