January 2008

Documenting skills is value-add

ISA certification provides an objective, third-party assessment, and confirmation of a person's skills. It gives manufacturing and factory staff the opportunity to differentiate themselves from their peers and gain recognition. InTech covers two certification areas in its monthly certification review.

ISA Certified Automation Professional (CAP) program

Certified Automation Professionals (CAPs) are responsible for the direction, design, and deployment of systems and equipment for manufacturing and control systems.

The following question comes from the CAP study guide, Performance Domain I, Feasibility Study: Identify, scope, and justify the automation project 
CAP question

Given the following diagram, what is the transfer function for C(s)/R(s)?




CAP answer

The correct answer is A, jan8

The numerator is the product of the transfer functions between the input and output, which are "R" and "C," respectively in this case. The denominator is one plus the product of all the transfer functions.

Reference: George Ellis; Control System Design Guide; Academic Press, 2000.

A transfer function is a mathematical representation of the relationship between the input and output of a system. In control engineering and control theory, one derives the transfer function using the Laplace transform.

The transfer function was the primary tool used in classical control engineering. However, it has proven to be unwieldy for the analysis of multiple-input multiple-output (MIMO) systems.

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.

This question comes from the Level I study guide, Domain 3, Troubleshooting. Level I represents a professional who has a five-year total of education, training, and/or experience. 

CCST question

Which orifice plate is used to eliminate damming of material at the top or bottom of the pipe?

A. Concentric
B. Round-edged
C. Quadrant-edged
D. Segmental

CCST answer

An orifice plate is a flow-path restriction that we use in flow detection. They are in a straight run of smooth pipe away from valves and fittings so they do not interfere with the restrictor and readings.

The pressures on opposite sides of the plate are different, and the difference in pressures is proportional to the flow rate.

Segmental and eccentric plates have many similarities as to function. The segmental portion of the orifice mitigates the damming of foreign materials on the upstream side of the orifice.

Eccentric orifice plates work to stop damming as well. The best answer to this question is D, segmental. 


Nicholas Sheble (nsheble@isa.org) writes and edits Certification Review.