Owner's manual

FOUNDATION
TM
Fieldbus Blocks Manual
9-6
Figure 9-2. PID Function Block
Setpoint Selection
Filtering The filtering feature changes the response time of the device to smooth
variations in output readings caused by rapid changes in input. You can
configure the filtering feature with the FILTER_TYPE parameter, and
you can adjust the filter time constant (in seconds) using the
PV_FTIME or SP_FTIME parameters. Set the filter time constant to
zero to disable the filter feature.
Feedforward Calculation The feedforward value (FF_VAL) is scaled (FF_SCALE) to a common
range for compatibility with the output scale (OUT_SCALE). A gain
value (FF_GAIN) is applied to achieve the total
feedforward contribution.
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.
Operator
Setpoint
SP_HI_LIM
SP_LO_LIM
SP_RATE_UP
SP_RATE_DN
Setpoint
Limiting
Rate
Limiting
Auto
Man
Auto
Man
Cas
Cas
FIELDBUS-FBUS_01A