Instrument Technician Practice Exam Flashcards

A collection of practice questions and answers for Instrument Technician certification, covering loop checks, electrical troubleshooting, valve mechanics, and piping standards, and safety procedures.

In commissioning, when is the BEST time to document each loop check?

At the time each test is completed

On which type of service must Teflon paste NEVER be used?

Oxygen service

If a 120VAC input measures 120V between hot and ground but 72V between hot and neutral, what is the most likely cause of the 24VDC power supply failure?

Lost the neutral

Under what condition does tube gain increase?

When the bend radius increases

What temperature measuring device produces a voltage as the temperature changes?

Thermocouple

In which document can a pressure piping code be found?

ANSI B 31.1

What is the preferred method for marking tubing before cutting?

Mark the tube with a felt tip pen

Which of the following is an example of a direct measurement indicator?

Sight glass

Which activity is NOT typically performed during loop checks?

Proving

If a $75V$ DC potential is applied to a $25\text{ ohm}$ load, what is the circuit current?

$$3.0\text{ amps}$$

When does a valve exhibit linear-flow characteristics?

When the flow corresponds directly to the valve stem position

What is the circuit current if $45\text{ VDC}$ is applied to a $250\text{ ohm}$ load?

$$0.18\text{ amp}$$

Which of these valves is NOT used to regulate flow?

Gate

What is the term for the desired value of a dynamic variable in a process?

Set point

What is an acceptable tool for marking 360 degrees around the outside of tubing?

Rubber band

What process variable is defined as the amount of force exerted by a substance over a given unit of measure?

Pressure

Storage of steel wool is considered a fire hazard when kept near which items?

Batteries

What is considered the MINIMUM value of the measured process range?

Zero input value

What does a bubbler system measure?

Head pressure

What should be used to prevent travel damage to a limit switch?

Mechanical stop

In a controller, what does automatic control describe?

The final control element responding to the error signal or change in process

How must soft rolled tubing be unrolled and straightened?

By hand

Where can an instrument fitter find the proper method to connect an instrument to a process tap?

On an installation detail

Which part of a control valve controls the plug proportionally to the controller's output?

Valve positioner

What should workers always assume regarding electrical equipment and lines?

They are energized until proven otherwise

What is the main function of a transducer?

To convert one signal form into another signal form

What type of liquid is used for degreasing electronic equipment?

Isopropyl alcohol

If a large self-operated regulator is sluggish during load changes, what is the first step to improve operation?

Raise the outlet pressure

What is a critical step during acid cleaning a tubing run after installation?

Drain low points

How is the setpoint changed on a field mounted controller?

Manually

When using a multimeter to drive loop current, what should the meter be set to?

Output mA

Why might a multimeter read voltage correctly but fail to read milliamp current even when leads are correct?

The meter's current fuse is blown

How much should the cut ends of packing rings be staggered during installation?

90 Degrees

As a rule of thumb, how much will $1/2\text{ inch}$ tubing gain for every 90-degree bend?

$$3/8\text{ inch}$$

What does NOT need to be checked when receiving an instrument?

The shipping date from the manufacturer

Where are rubber gaskets typically used?

In low pressure/low temperature systems

What is the purpose of an instrument index?

To list every instrument used on a project

What are the two common types of material used for shielding?

Foil and braided

What type of control does an employee have over energy potential if they hold the power plug after removing it from the outlet?

Exclusive control

In relation to valve actuators, what does the term "fail open" mean?

When the actuator power is lost, the valve will open

What should be done if Hastelloy "B" tubing is mixed with 316 SS tubing and neither is labeled?

Report the problem to the supervisor and have the tubing PMI'd (Positive Material Identification)

What two factors determine the static head pressure near the bottom of a tank?

The height of the level and the specific gravity

Which two parameters are best for troubleshooting a transmitter with a non-working RTD?

DC voltage and resistance

Which part of an instrumentation installation drawing lists the required fittings?

Materials list

Using the equation $Absolute\text{ vacuum pressure} = barometric\text{ pressure} - vacuum\text{ gauge reading}$, find the absolute pressure if the gauge reads $22.2\text{ inHg}$ and barometric pressure is $27.68\text{ inHg}$.

$$5.48\text{ inHg}$$

What is the primary factor affecting the severity of an electrical shock?

Amount of current in the body

If a sump pump motor continues to run after the tank is empty, what is the likely cause in the float switch?

Contacts are welded closed

Where are the specific types of gaskets and gasket materials for a project listed?

A section of the specifications

What is the preferred medium to remove debris from a new instrument air line prior to service?

Air

A strain gauge measures external force by detecting a change in which property?

Resistance