The post AutoQuiz: Characteristics of an Industrial Controller first appeared on the ISA Interchange blog site.
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.
a) reverse acting
b) direct acting
d) fail safe
e) none of the above
The correct answer is B, direct acting. For a direct-acting controller, the resulting output movement is in the same direction as the movement of the process variable.
Here is an example of a direct-acting controller. If we have an air-to-open tank outlet valve, as the level rises (PV) in the tank, we would want the outlet valve to open (controller output increases).
Reference: Goettsche, L.D. (Editor), Maintenance of Instruments and Systems, 2nd Edition
Source: ISA News