Rockwell Automation 1771-QC , D17716.5.25 SER/B SERVO POS - Manual (Page 226)

Glossary
Appendix A
AĆ2
Closed-Loop: A signal path in which results are fed back for comparison
with desired values to regulate system behavior.
Current Sink: A signal sending device that shunts current to ground.
Current Source: A signal sending device that generates positive current.
Data Table: The part of processor memory that contains I/O values and
files, where data is monitored, manipulated, and changed for control
purposes.
Digital: Representation of data in discrete numerical form.
Digital-to-Analog (D/A) Conversion: Production of an analog signal,
whose instantaneous magnitude is proportional to the value of the digital
input.
Encoder (Incremental): A rotary device that transmits a fixed number
of pulses per revolution.
Feedback: The signal or data transmitted to the PC from a controlled
machine to denote its response to the command signal.
Feedback Device: An element of a control system that converts linear or
rotary motion to an electrical signal for comparison to the command
signal, e. g., encoder.
Feedback Loop: A closed signal path, in which feedback is compared
with the commanded value to obtain a corrective error signal.
Feedback Resolution: The smallest increment of dimension that the
feedback device can distinguish and reproduce as an electrical output.
Feedback Signal: The measurement signal indicating the value of a
directly controlled variable, which is compared to the commanded value
to obtain the corrective error signal.
Feedforward Control: Action in which information concerning
upstream conditions is converted into corrective commands to minimize
the effect of the disturbances.