Super Systems 3 Series - Manual (Page 55)

Series 3 Operations Manual
55
11.3.6 Autotune From Below SP – Heat Only
The sequence of operation for a heat only loop is the same as that previously described for a heat/cool loop except that the
sequence ends at ‘F’ since there is no need to calculate ‘R2G’.
At ‘F’ autotune is turned off and the process is allowed to control using the new control terms.
Relative cool gain, ‘R2G’, is set to 1.0 for heat only processes.
For a tune from below setpoint ‘CBLO’ is calculated on the basis of the size of the overshoot (assuming it was not set to Auto in
the initial conditions). CBHI is then set to the same value as CBLO.
Note: As with the heat/cool case, Autotune can also occur when the initial PV is above SP. The sequence is the same as tuning
from below setpoint except that the sequence starts with natural cooling applied at ‘B’ after the first one minute settling time.
In this case CBHI is calculated – CBLO is then set to the same value as CBHI.
E
A – B = 1 min.
C D F
First
overshoot
Target Setpoint
PV
Tune Control Point
High Output
Zero Output
Peak to
Peak
Hysteresis
F - End of
Autotune
D to F -
calculate
PID
C to D -
calculate CBL
A - Start of
Autotune
B