Emerson Rosemount OCX8800 Instruction Manual page 162

Section 7: Foundation
Fieldbus
April 2017
Tracking
You enable the use of output tracking through the control options. You can set control options
in Manual or Out of Service mode only.
The Track Enable control option must be set to True for the track function to operate. When the
Track in Manual control option is set to True, tracking can be activated and maintained only
when the block is in Manual mode. When Track in Manual is False, the operator can override the
tracking function when the block is in Manual mode. Activating the track function causes the
block's actual mode to revert to Local Override.
The TRK_VAL parameter specifies the value to be converted and tracked into the output when
the track function is operating. The TRK_SCALE parameter specifies the range of TRK_VAL.
When the TRK_IN_D parameter is True and the Track Enable control option is True, the TRK_VAL
input is converted to the appropriate value and output in units of OUT_SCALE.
Output Selection and Limiting
Output selection is determined by the mode and the setpoint. In Automatic, Cascade, or
RemoteCascade mode, the output is computed by the PID control equation. In Manual and
RemoteOutput mode, the output may be entered manually. You can limit the output by
configuring the OUT_HI_LIM and OUT_LO_LIM parameters.
Bumpless Transfer and Setpoint Tracking
You can configure the method for tracking the setpoint by configuring the following control
options (CONTROL_OPTS):
•
•
When one of these options is set, the SP value is set to the PV value while in the specified mode.
You can select the value that a master controller uses for tracking by configuring the Use PV for
BKCAL_OUT control option. The BKCAL_OUT value tracks the PV value. BKCAL_IN on a master
controller connected to BKCAL_OUT on the PID block in an open cascade strategy forces its OUT
to match BKCAL_IN, thus tracking the PV from the slave PID block into its cascade input
connection (CAS_IN). If the Use PV for BKCAL_OUT option is not selected, the working setpoint
(SP_WRK) is used for BKCAL_OUT.
You can set control options in Manual or Out of Service mode only. When the mode is set to
Auto, the SP will remain at the last value (it will no longer follow the PV.
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SP-PV Track in Man — Permits the SP to track the PV when the target mode of the block
is Man.
SP-PV Track in LO or IMan — Permits the SP to track the PV when the actual mode of the
block is Local Override (LO) or Initialization Manual (IMan).
Instruction Manual
IM-106-880C, OI
Setpoint Selection and
Limiting