7
5
OPERATING LEVEL
5.1
Operating Page Introduction
5.1.1
Set Point Tracking
With
set point tracking
enabled (in the
Set Points Page
), the Local set point value tracks the
process variable when the controller is in Manual control mode. In this mode of operation the
set point limits do not apply. If the set point value is outside its limits when Automatic control
mode is selected, the local set point remains outside its limits and can only be adjusted in one
direction, towards its limits. Once inside the limits they apply as normal.
With
remote set point tracking
enabled, the Local set point tracks the remote set point value
when in the remote set point mode. In this mode of operation the Local set point limits do not
apply. If the set point value is outside its limits when the Local set point value is selected, the
Local set point remains outside its limits and can only be adjusted in one direction, towards its
limits. Once inside the limits they apply as normal.
5.1.2
Auto/Manual Transfer
All auto-to-manual transfers are bumpless. If the Local set point is used and set point tracking
is enabled, all manual-to-auto transfers are bumpless, since the set point is always at the same
value as the process variable. Without set point tracking enabled, the response following a
manual-to-auto transfer depends on the control settings. With an integral action setting the
output is ramped up or down to remove any process variable offset from the set point (providing
the process variable is within the proportional band). If the integral action is off, the output may
step to a new value when the controller is transferred back to Automatic control mode.
With remote set point tracking enabled, the control set point switches automatically from
Remote to Local when Manual mode is selected.
5.1.3
Heat/Cool Control – Fig. 6.3
When in Automatic control mode both the heat and cool outputs are turned off when in the
Output Off Hysteresis Band. In Manual control mode the Output Off Hysteresis Band has no
effect. If the PID output is within the Off Hysteresis Band when the controller is returned to auto
control mode, the Off Hysteresis Band has no effect until either the PID output goes outside the
band or becomes equal to the Crossover Value.
Fig. 5.1 Set Point Type Selection Facility (see Section 5.2 overleaf)
100.3
110.5
LOCAL
110.5
LOCAL
bALNCE
rEMOtE
dUAL
or
Control Set Point frame
Balance Set Point – shows the difference
between the Local and Second Set Point values
(remote or dual), i.e.
Balance = Second set point – Local set point
To adjust Local or Dual Set Point value
