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.
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
e) none of the above
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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, 2nd Edition