Azbil SDC36 - Page 90

5-30
Chapter 5. DETAILED DESCRIPTION OF EACH FUNCTION
PV
SP
2/3
1/3
Insucient
stability
AT start
Time
Normal end
Stable
cycle
In the Heat/Cool control, the AT function is run in the status that both the heat MV
and cool MV are operated.
In the first half, the MV is changed to the MV low limit/MV high limit. In the
latter half, the MV is changed in a slightly narrow range.
The following Figure shows an example of the AT execution when the Heat/Cool
control deadband is 0.0%, Heat/Cool control change point is 50.0%, MV low limit
is 0.0%, and MV high limit is 100.0%:
MV (%)
100.0
Time
50.0
0.0
Heat MV (%)
100.0
Time
50.0
0.0
Cool MV (%)
100.0
Time
50.0
0.0
PV
Time
SP change
point
AT is running.
Handling Precautions
• Before starting the AT function, put the PV input and/or actuator (heater
power, etc.) in the controllable status.
• When the control method is set at “ON/OFF control” ([
CtrL
] = 0), the AT
function cannot be started. To operate the AT function, set the control
method to “Fixed PID” ([
CtrL
] = 1).
• To start the AT, it is absolutely necessary that the operation is in the
READY mode and AUTO mode, and no PV input errors occur.
• If the mode is changed to the READY mode or MANUAL mode or if the PV
input error or power failure occurs during execution of the AT function,
the AT function is stopped without changing of the PID constants.