Glossary
NI 7350 User Manual G-6 ni.com
O
open collector A method of output capable of sinking current, but not sourcing current.
open-loop A motion control system where no external sensors (feedback devices) are
used to provide position or velocity correction signals.
P
PCI peripheral component interconnect—A high-performance expansion bus
architecture originally developed by Intel to replace ISA and EISA. PCI is
achieving widespread acceptance as a standard for PCs and workstations;
it offers a theoretical maximum transfer rate of 132 MB/s.
PID control loop proportional-integral-derivative control loop—A control method in which
the controller output is proportional to the error, the error time history, and
the rate at which the error is changing. The error is the difference between
the observed and the commanded values of a variable that is under control
action.
PIVff control loop proportional-integral-velocity feed forward control loop—A control
method that operates with zero derivative gain and either velocity feedback
or a velocity block amplifier.
port (1) A communications connection on a computer or a remote controller;
(2) A digital port, consisting of eight lines of digital input and/or output.
position breakpoint Position breakpoint for an encoder can be set in absolute or relative
quadrature counts. When the encoder reaches a position breakpoint, the
associated breakpoint (position compare) output immediately transitions.
power cycling Turning the host computer off and then back on, which causes a reset of
the motion control board.
PWM pulse width modulation—A method of controlling the average current in a
motor phase winding by varying the on-time (duty cycle) of transistor
switches.
PXI PCI eXtensions for Instrumentation—A rugged, open system for modular
instrumentation based on CompactPCI, with special mechanical, electrical,
and software features. The PXIbus standard was originally developed by
National Instruments in 1997, and is now managed by the PXIbus Systems
Alliance.