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

If the proportional band on a controller is 100 percent, then the controller gain is equal to:

A. 0.50
B. 0.20
C. 1
D. 100

CCST Answer

The correct answer is C, "1." The proportional band is defined as the amount of change in input (or deviation), as a percent of span, required to cause the control output to change from 0 percent to 100 percent.

Gain is a unitless number that defines the ratio of the change in output, due to proportional control action, to the change in input, in percent of span.

CCST fig 1

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

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