Technical information

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Glossary
Motor, DC Brushless
A type of direct current motor that utilizes electronic commutation rather than brushes to transfer current.
Usually refers to a motor commutated with hall effect sensors which results in trapezoidal commutation
current signals.
Motor, DC Permanent Magnet
A DC motor utilizing permanent magnets to produce a magnetic field and a commutator on the stator. Has
linear torque speed characteristics.
Motor, Stepping
A specialized AC motor that allows discrete position steps without feedback. Normally used for non-
critical, low power applications, since positional information is easily lost if acceleration or velocity limits
are exceeded. Load variations can also cause loss of position. If encoders are used, these limitations can
sometimes be overcome.
Motor Torque Constant (Kt)
The ratio of the motor torque to motor input current.
NC, Numerical Control
Usually refers to any type of automated equipment or process used for multiple axis contouring or
positioning.
Negative Feedback
The type of feedback used in a closed loop system where the output value is inverted and combined with the
input to be used to stabilize or improve system characteristics.
No Load Speed
Maximum motor speed with no external load.
Open Collector
A term used to describe a signal output from a transistor. An NPN (Negative-Positive-Negative) type open
collector output grounds the output point when active. A PNP (Positive-Negative-Positive) open collector
output supplies positive voltage to the output when active.
Open-Loop System
A system where the command signal results in actuator movement but, because the movement is not sensed,
there is no way to correct for error. Open loop means no feedback. Typically refers to stepping motor
systems or velocity only systems.
Operator Interface
A device that allows the operator to communicate with a machine. This device typically has a keyboard or
thumbwheel to enter instructions into the machine. It also has a display device that allows the machine to
display messages.
Opto-isolated
A method of sending a signal from one piece of equipment to another without the usual requirement of
common ground potentials. The signal is transmitted optically with a light source (usually a Light Emitting
Diode) and a light sensor (usually a photosensitive transistor). These optical components provide electrical
isolation.