March/April 2014
Certification Review

ISA Certified Control Systems Technician (CCST) Program

CCST

Certified Control System Technicians (CCSTs) calibrate, document, troubleshoot, and repair/replace instrumentation for systems that measure and control level, temperature, pressure, flow, and other process variables.

CCST question

A switch placed to sense when a mechanism has reached the end of its travel is called:

A. a limit switch
B. a terminator
C. a solenoid
D. Form C contacts

CCST Answer

The correct answer is A, “a limit switch.” Limit switch is a general term to describe the class of devices that are used to detect the end of travel of a valve, louver, or any other item that may be in motion. Limit switches are now also commonly used to detect jams in conveyor systems or to prove the position of a device or component (such as a gate or lane rail).

Answer B is not correct; a terminator is an electrical device that is placed at the end of a fieldbus trunk line to prevent reflections of electrical signals back through the cable.
Answer C is not correct; a solenoid is an electrical inductive device that converts energy into linear motion.

Answer D is not correct; Form C contacts refer to a type of electrical contact that is composed of a normally closed and a normally open contact operated by the same device, with a common electrical connection.

Reference: Goettsche, L. D. (Editor), Maintenance of Instruments and Systems, Second Edition, ISA, 2005.