CCST Instrumentation & Process Control 2

Question 1

A thermocouple produces a millivolt output that drifts with ambient temperature changes. Which correction method is most commonly used to compensate for this error?

Accepted Answer

Cold junction compensation

Answer

Cold junction compensation corrects for the reference junction temperature, which fluctuates with ambient conditions and introduces measurement error.

Question 2

In a pneumatic control system, what does an I/P transducer convert?

Accepted Answer

Current (4-20 mA) to pneumatic pressure signal (3-15 psi)

Answer

An I/P (current-to-pressure) transducer converts a 4-20 mA electrical signal into a 3-15 psi pneumatic output to drive control valves.

Question 3

Which type of control valve trim is specifically designed to provide equal percentage flow characteristics?

Accepted Answer

Parabolic or characterized cam trim

Answer

Parabolic or characterized cam trim shapes the relationship between valve travel and flow so that each equal increment of travel produces an equal percentage increase in flow.

Question 4

A differential pressure transmitter installed on an orifice plate reads higher than actual flow. What is the most likely cause?

Accepted Answer

The orifice plate is installed backwards

Answer

An orifice plate installed backwards reverses the high/low pressure taps, causing the transmitter to sense incorrect differential pressure and over-read.

Question 5

In ISA S5.1 symbology, a circle on a process flow diagram with the letter 'FIC' indicates which instrument function?

Accepted Answer

Flow indicating controller

Answer

Per ISA S5.1, 'F' = flow, 'I' = indicating, 'C' = controller, so FIC denotes a flow indicating controller.

(CCST) Certified Control Systems Technician Practice Test

(CCST) Certified Control Systems Technician Practice Test

CCST Instrumentation & Process Control 2