FE Mechanical Measurements, Instrumentation, and Controls

Knowledge area 13 of the FE Mechanical exam: 5–8 of the 110 questions. The subtopics NCEES lists, how they are tested and worked practice problems with solutions.

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110 questions on the real 5 hours 20 minutes clock, weighted to the NCEES specifications, with a score by knowledge area and a worked solution for every answer.

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What the specification lists

Sensors and transducers
Control systems (e.g., feedback, block diagrams)
Dynamic system response
Measurement uncertainty (e.g., error propagation, accuracy, precision, significant figures)

From the NCEES FE Mechanical CBT exam specifications, knowledge area 13.

Line drawing of a control panel with dial gauges, a thermocouple probe and a data logger

How Measurements, Instrumentation, and Controls is tested

Instrumentation questions cover sensors (thermocouples, RTDs, strain gauges and bridges), sampling and A/D resolution, block diagrams and closed-loop transfer functions, first- and second-order response and error propagation. The Reference Handbook section on instrumentation, measurement, and control has the relationships you need.

On exam day the relationships you need are in the Reference Handbook section on Instrumentation, Measurement, and Control. The handbook is the only reference allowed, so practice finding each formula in it rather than memorizing a separate sheet.

Start the free Measurements, Instrumentation, and Controls drill

FE Mechanical Measurements, Instrumentation, and Controls practice problems

Work each problem with your calculator and the handbook, then open the solution.

Problem 1 · Sensors and transducers

A type K thermocouple has an average sensitivity of 41 μV/°C over the range of interest; treat its output as linear. With the reference junction at 25°C, the voltmeter reads 12.3 mV. The measuring-junction temperature is most nearly:

A.25.3°C
B.275°C
C.300°C
D.325°C

Show the answer and solution

Answer: D: 325°C

A thermocouple measures the temperature difference between its junctions: ΔT = 12.3 mV/0.041 mV/°C = 300°C. The measuring junction is 300°C above the 25°C reference, so T = 325°C. Ignoring the reference junction (300°C) is the most common error.

Sensors and transducers · Reference Handbook: Instrumentation, Measurement, and Control

Problem 2 · Dynamic system response

A first-order pressure transducer starts at steady state and is subjected to a step change in pressure. Its output reaches 50% of the final change 2.10 s after the step. Enter the time constant in seconds to two decimal places.

Fill in the blank: answer in s.

Show the answer and solution

Answer: 3.03 s (accepted 2.98 to 3.08)

For a first-order step response, the fraction completed is 1 − e^(−t/τ). Setting it to 0.50 gives t = τ ln 2, so τ = 2.10/0.6931 = 3.03 s.

Dynamic system response · Reference Handbook: Instrumentation, Measurement, and Control

Problem 3 · Control systems

A unity negative-feedback system has the forward-path transfer function G(s) = 20/[(s + 1)(s + 4)]. For a unit step input, the steady-state error is most nearly:

A.0.0476
B.0.167
C.0.200
D.0.833

Show the answer and solution

Answer: B: 0.167

The position error constant is K_p = G(0) = 20/(1 × 4) = 5. For a type-0 system with a unit step, e_ss = 1/(1 + K_p) = 1/6 = 0.167. The output settles at 5/6 = 0.833.

Control systems · Reference Handbook: Instrumentation, Measurement, and Control

Problem 4 · Measurement uncertainty

Select all that apply.

A pressure gauge is checked against a 500.0 kPa reference standard. Five readings are 512.1, 511.8, 512.0, 512.2 and 511.9 kPa. Which statements are true? Select all that apply.

A.The gauge is precise: the readings agree closely with one another.
B.The gauge is inaccurate: the readings show a systematic error of about +12 kPa.
C.The error is mainly random.
D.Averaging a larger number of readings would remove the error.
E.A calibration offset correction would address most of the error.

Show the answer and solution

Answer: A: The gauge is precise: the readings agree closely with one another.; B: The gauge is inaccurate: the readings show a systematic error of about +12 kPa.; E: A calibration offset correction would address most of the error.

The readings span only 0.4 kPa (high precision), but their mean, 512.0 kPa, is 12 kPa above the standard (poor accuracy). That bias is systematic: averaging reduces random scatter but leaves a constant offset unchanged, while a calibration correction of about −12 kPa removes it.

Measurement uncertainty · Reference Handbook: Instrumentation, Measurement, and Control

More FE Mechanical practice problems from every knowledge area

Sit the full exam under the real clock

Take a full timed FE Mechanical practice exam

110 questions on the real 5 hours 20 minutes clock, weighted to the NCEES specifications, with a score by knowledge area and a worked solution for every answer.

Or start the free Measurements, Instrumentation, and Controls drill

Common questions

How many Measurements, Instrumentation, and Controls questions are on the FE Mechanical exam?

The NCEES FE Mechanical specification lists 5–8 questions on Measurements, Instrumentation, and Controls, out of 110. Every examinee gets the same number per knowledge area.

What does Measurements, Instrumentation, and Controls cover on the FE Mechanical exam?

Sensors and transducers; Control systems (e.g., feedback, block diagrams); Dynamic system response; Measurement uncertainty (e.g., error propagation, accuracy, precision, significant figures).

Where are the Measurements, Instrumentation, and Controls formulas on exam day?

In the NCEES FE Reference Handbook, which appears on screen during the exam: the Instrumentation, Measurement, and Control section. Practice with your free copy from MyNCEES so you know where each relationship sits.

Original independent practice questions written to the published NCEES exam specifications. Not affiliated with or endorsed by NCEES (National Council of Examiners for Engineering and Surveying).