ABB C300, Operating Manual

Page: 22 / 36

20
6.3 Self-tune Diagnostic Messages
…6 TUNING LEVEL
Table 6.1 Self-tune Error/Diagnostic Messages
Pb–INt
HI–LMt
SP tOO
CLOSE
INCrSE
StEP
SLO
PrCESS
NOISY
CLOSE
SP tOO
PrCESS
INPUt
LIMItS
S–tUNE
CAUtN
S–tUNE
FAIL
Flashing
with
or
or
Flashing
with
or
or
or
Message
Explanation Action
The process is too slow for the
self-tuning to work correctly.
The input failure level has been
exceeded, possibly due to a
broken sensors or the process
has exceeded one of the self-
tune limits.
With
'At Set Point'
tuning, the
ratio of process oscillation to
hysteresis value is too small for
best results.
The self-tune process has
selected a proportional band or
integral action time above the
high limits of these parameters
so the high limit has been used. B e c a u s e o f t h e p r o c e s s
characteristics, re-trying the self-
tuning process is unlikley to
improve the calculated control
parameters.
Restart self-tune with a larger
output step size or a smaller
hysteresis value. Hysteresis
must be at least equal to and
preferably greater than process
noise.
If possible, use a larger output
step value.
Check input wiring to find the
cause of the failure or restart self-
tuning with a smaller output step
size.
The process variable signal is
excessively 'noisy'. Check input wiring to try and find
the source of the problem. If the
process is changing rapidly then
allow it to settle before re-trying
the self-tuning process.
With
'Start-up'
tuning, the
process variable is <10% of the
display range, below the control
set point.
Allow the process variable to
move further below the control
set point before re-trying the
'Start-up'
self-tuning facility.
Alternatively, use the
'At Set
Point'
self-tune facility.
With
'Start-up'
tuning, although
the control set point was >10%
of the display range above the
process variable, it may still be
too close to allow the self-tune
facility to determine the process
characteristics accurately.
If desired, allow the process
variable to move further below the
control set point (by changing the
control output in the manual
control mode) before re-trying
'Start-up'
self-tuning. Alternatively,
use the
'At Set Point'
self-tune
facility.