4.6 PID Block
The PID Function Block contains the logic necessary to per-
form Proportional/Integral/Derivative (PID) control. The block
provides filtering, set point limits and rate limits, feedforward
support, output limits, error alarms, and mode shedding.
Although most other function blocks perform functions specific
to the associated device, the PID block may reside in any device
on the network. This includes a valve, a transmitter, or the host
itself.
The Enhanced Model 705 3X PID Block implementation fol-
lows the specifications documented by the Fieldbus Foundation.
ACK_OPTION: Used to set auto acknowledgement of
alarms.
ALARM_HYS: The amount the alarm value must return to
before the associated active alarm condition clears.
ALARM_SUM: The summary alarm is used for all process
alarms in the block.
ALERT_KEY: The identification number of the plant unit.
ALG_TYPE: Selects filtering algorithm as Backward or
Bi-linear.
BAL_TIME: The specified time for the internal working
value of bias to return to the operator set bias.
BKCAL_IN: The analog input value and status for another
blocks BKCAL_OUT output.
BKCAL_HYS: The amount the output must change away
from its output limit before the limit status is turned off,
expressed as a percent of the span of the output.
BKCAL_OUT: The value and status required by the
BKCAL_IN input for another block.
BLOCK_ALM: Used for all configuration, hardware, con-
nection failure, or system problems in the block.
BLOCK_ERR: Reflects the error status associated with the
hardware or software components associated with a block.
BYPASS: Used to override the calculation of the block.
CAS_IN: The remote setpoint value from another block.
CONTROL_OPTS: Allows one to specify control strategy
options.
DV_HI_ALM: The DV HI alarm data.
DV_HI_LIM: The setting for the alarm limit used to
detect the deviation high alarm condition.
DV_HI_PRI: The priority of the deviation high alarm.
DV_LO_ALM: The DV LO alarm data.
32
57-640 Eclipse Guided Wave Radar Transmitter - FOUNDATION fieldbus
™
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