ISA Certified Control Systems Technician (CCST) program


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

Which troubleshooting technique replaces suspected bad components until the problem is found?
A. Substitution method
B. Consultation method
C. "Remove and conquer" method
D. Fault insertion method

CCST Answer

The correct answer is A, substitution method. The substitution method substitutes a known good component for a suspected bad component. Substitution may reveal the component that is the cause of the problem.

Consultation (answer B), also known as the “third head” technique, means you use a third person who has advanced knowledge about the system or the principles (perhaps someone from another department or an outside consultant) to help troubleshoot the problem.

The “remove and conquer” method (answer C) involves removing devices one at a time, which may help find certain types of problems, like overcapacity on an instrument bus.

The fault insertion method (answer D) is usually used during system testing, where faults are inserted into the system, so that system response can be observed.

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