Rockwell Automation 1771-PD PID MODULE (+DU) - Manual (Page 5)

Introduction
Chapter 1
1Ć2
Capabilities
The PID module can control one or two PID closed loops. The two loops
can be independent or linked together by and advanced control function
such as cascade or decoupling. Expanded loop features can be chosen in
addition to standard features to suite the application. All features are
software selectable with the exception of the I/O range, the source of +5V
DC, and the fault response to a hardware failure (which are selected using
internal programming plugs). Write block transfers to the module allow
program logic to enable the following features:
Standard features for input conditioning
detect the loss of process variable input
read the process variable at the PC processor
substitute a value from the PC processor for the process variable
take the square root of the process variable
\\digitally filter the process variable
Standard control features
select direct or reverse acting control
download a set point from the PC processor
limit and/or set an alarm on the error signal
download a dead band value from the PC processor
perform error dead band (zero crossing)
set an alarm when the error exceeds the dead band
select the control mode: proportional only, integral only, proportional
and integral, proportional and derivative, or all three
select error or error squared conditioning of the proportional and/or
integral error
select whether the derivative function operates on the error or the
process variable
set an alarm on the proportional term
limit and/or set an alarm on the integral term
limit and/or set an alarm on the derivative term
Standard features for output conditioning
limit and/or set an alarm on the PID algorithm output
read the PID algorithm output at the PC processor
download an output value from the PC processor
interface directly with a manual control station (bumpless transfer)
hold the PID algorithm output for independent loop tuning
hold the bias/feed forward term for independent loop tuning