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

You have a standard pneumatic instrument loop with a span of 200 units. What is the steady state gain?  

A. 0.06 psig/unit
B. 0.07 psig/unit
C. 0.08 psig/unit
D. 0.12 psig/unit

 

CCST Answer

The correct answer is A, 0.06 psig/unit.

Gain is defined in control theory as the change in input divided by the change in output. In this case, the gain can be calculated as follows:

Gain = (full range change in input) / (full range change in output)

= (15 psig - 3 psig, for a pneumatic loop) / 200 units of change

= (15 - 3) / 200

= 12 / 200

= 0.06 psig/unit

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