Industrial Electronics Glossary

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CAD Computer-aided design (also known as computer-aided drafting). A system developed to create drawings on a computer.

CD-ROM Read-only memory on a compact disk.

central processing unit (CPU) The microprocessor that is the main controller for a PLC system or other computer controlled system.

centrifugal switch A switch that is connected in series with the start winding of a single-phase ac motor and is mounted in its end plate. The purpose of this switch is to open its contacts at approximately 90 percent of full rpm to disconnect the start winding of the motor from the source of voltage. The switch will close when the motor is de-energized and slows to a stop.

circuit breaker An electrical device specifically designed to protect against overcurrent. The circuit breaker is similar to a fuse in that it protects, but it is different in that it can be reset.

closed-loop system A control system that uses a feedback signal. CMOS Complementary metal-oxide semiconductor.

CNC Computerized numerical control. A control system where a computer guides a machine like a mill or lathe to various mathematical points in a two- or three-dimensional plane.

cogging A condition in which a motor does not rotate smoothly, but "steps" or "jerks" from one position to another during shaft revolution.

cold-junction compensation An electronic circuit that is used with a thermocouple to simulate the value of a reference signal of 32°F or 0°C.

common-mode rejection The ability of a differential analog input to cancel a common-mode signal expressed in 3B.

common-mode voltage A voltage that appears in common with both input terminals of a differential analog input with respect to ground.

commutator A cylindrically shaped assembly that is fastened to the shaft of a motor or generator and is considered part of the armature assembly. It consists of segments of "bars" that are electrically connected to the two ends of one or more armature coils.

contactor One or more sets of contacts that are opened or closed by a magnetic coil. The contactor is similar to a relay but normally larger. By definition, the contactor is rated for more than 15 A.

converter A device or circuit for changing ac to dc. This is accomplished through a diode rectifier or thryristor rectifier circuit.

counter emf The induced voltage in an ac or dc motor that opposes the applied voltage.

CPU Central processing unit (see central processing unit).

CRT terminal A display terminal containing a cathode ray tube.

CTS Clear-to-send. A signal that tells the transmitting device to start transmitting data.

current limiting An electronic method of limiting the maximum current available to the motor.

current transformer A transformer that is used primarily as a step-down transformer to indicate the amount of current flowing in a motor drive or other large-current application.

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