This automation industry quiz question comes from the ISA Certified Control Systems Technician (CCST) program. Certified Control System Technicians calibrate, document, troubleshoot, and repair/replace instrumentation for systems that measure and control level, temperature, pressure, flow, and other process variables. Click this link for more information about the CCST program.
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
e) none of the above
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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.
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.
Reference: Goettsche, L.D. (Editor), Maintenance of Instruments and Systems, 2nd Edition