Azbil SDC36 User Manual

5-31
Chapter 5. DETAILED DESCRIPTION OF EACH FUNCTION
• On position proportional control models (with code R1 in the control output
segment of the model No.), the factory setting for
At-d
(AT derivative time
adjust) in the Extended tuning bank is 0.00, and therefore the derivative
time is 0 seconds when AT is complete. To have the AT result affect control,
change the
At-d
setting to 1.00 and re-execute AT. For details,


Auto tuning (AT) (p.5-26).
• When the Heat/Cool control is not used, the MV becomes a value limited
by both ranges, one range is between the MV low limit at AT (
AT.OL
) and
MV high limit at AT (
AT.OH
), and the other is between the MV low limit
(
OL-
_) and MV high limit (
OH-
_) of the PID constant. When there are no
common portions in two ranges, the AT function is stopped automatically.
• When the Heat/Cool control is used, the MV becomes a value limited by
the MV low limit at AT (
At.OL
)/MV high limit at AT (
At.OH
), the heat MV
becomes a value limited by the MV low limit (
OL-
_)/MV high limit (
OH-
_)
of the PID constant, and the cool MV becomes a value limited by the Cool-
side MV low limit (
OL.
_
C
)/Cool-side MV high limit (
OH.
_
C
) of the PID
constant.
• When the MV low limit at AT (
AT.OL
)/high limit (
AT.OH
), MV low limit
(
OL-
_)/high limit (
OH-
_), Cool-side MV low limit (
OL.
_
C
)/Cool-side MV
high limit (
OH.
_
C
) of the PID constant are set unevenly, the PV may not be
changed up or down even though the MV is changed by the AT. In this case,
the AT is kept continued. Then, stop the AT manually, set the high limit and
low limit of the manipulated variable again, and restart the AT.
• The number of limit cycles and period of time from the AT start to AT end
may vary depending on the control subject.
• The MV ON and OFF are repeated several times during execution of the
AT function to perform the limit cycle. (The OFF operation described here
means MV limited by the MV low limit at AT ([
At.OL
]) or MV high limit
at AT ([
OL
]). The default setting before shipment is “0%”. Additionally,
the ON operation described here means MV limited by the MV high limit
at AT ([
At.OH
]) or MV high limit at AT ([
OH
]). The default setting before
shipment is “100%”. If this AT operation does not function correctly, take
either of the following measures:
(1) Change the MV low limit at AT ([
At.OL
]) or MV high limit at AT
([
At.OH
]) to an appropriate value, and then start the AT function.
(2) Set the PID constants manually without use of AT.
• The AT progress value can be seen in the operation display mode.
For details,


Operation displays in section 6 - 1 List of Operation Displays
(p.6-1).
When the Heat/Cool control is not used, the AT progress value
decrements from [4] during execution of the AT function and becomes [0]
at completion of the AT function.
When the Heat/Cool control is used, the AT progress value decrements
from [8] during execution of the AT function and becomes [0] at
completion of the AT function.
In both cases, the AT progress value may be “1” or “0” when the AT process
is in the transient status.
• Appropriate PID constants cannot be obtained depending on the control
subject. If this happens, set the PID constants manually.
• The MV ON/OFF change point determined when the AT function is
started does not change even though the SP is changed while the AT is
running. For details about AT function,


Auto tuning (AT) stop/start (p.5-11) and

Auto tuning (AT)
(p.5-26).

Azbil SDC36 Specifications

General

Brand	Azbil
Model	SDC36
Category	Controller
Language	English