This document appears to be a practice exam for an instrumentation and process control course. It contains 34 multiple choice or short answer questions covering various process control and instrumentation topics, including control system objectives, process variables, transfer functions, thermocouples, strain gauges, PID control, and programmable logic controllers. The questions require knowledge of concepts like control loops, signal conditioning, analog to digital conversion, and developing equations to interface different input and output signals.

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EE372 FinalExam
1. In process control the desired value of a system is referred to as
the__________?
A) Process variable
B) Controlled variable
C) The controller
D) The setpoint
2. In process control, the term the “process”, whatever it may be, may also be
referred to as the ______________.
A) Objective
B) Goal
C) Plant
D) Output
3. The device that exerts a direct influence on the process is called the
_____________.
A) Final control element
B) Basic element
C) The controller
D) The output
4. Control system objectives should include:
A) The system should be stable
B) The system should provide the best steady?state regulation.
C) The system should provide the best transient regulation
D) None of the above
E) All of the above
5. The response criterion that specifies that the amplitude of each peak of
each cyclic response be a quarter of the preceding peak is called_________.
A) Half wave
B) Full wave
C) Quarter ?amplitude
D) None of the above
6. The mathematical relationship between the input of a block and the output
of that block is known as the __________ __________.

2. A) Sine function
B) Log function
C) Transfer function
D) Algebraic function
7. The equation below describes the response of a __________________
order system.
A) First
B) Second
C) Last
D) Harmonic
8. The current through a RTD can cause the RTD to heat up. This factor is
accounted for by use of the ____________________.
A) Plank’s constant
B) Boltzman’s constant
C) Hooke’s Law
D) The dissipation constant
E) None of the above
9. Type J, T, K, E, S, and R are all thermocouple types. The letter
designates_______________.
A) the quality
B) the sensitivity
C) the temperature range
D) the corrosive specifications
10. Since Thermocouple voltages are small, great care should be taken to
protect against electrical noise by_________________.
A) Shielding
B) twisting the conductors
C) differential amplification
D) All of the above
E) None of the above
11. Strain gauges operate based on the change in ___________________ of
a metal under stress.
A) Capacitance
B) Inductance
C) Resistance
D) Impedance
12. The primary form of ____________ sensor is the accelerometer.
A) Temperature
B) Solar
C) Motion

3. D) ph
13. Flow across an orifice plate varies proportionally with the ___________ of
the differential pressure.
A) Square
B) Cube
C) Square root
D) Exponential
14. A rotameter, a moving vane flow meter and a turbine flow meter all place
________________ in the flow of the material.
A) An obstruction
B) An orifice
C) A Piezoelectric crystal
D) A Magnetic pickup
15. Elements of final control are:_______________.
A) Signal conversion
B) Actuator
C) Final control element
D) None of the above
E) All of the above
16. A _________________ is required to condition the signal from a
computer so that it might interact with process control equipment.
A) Stand by power source
B) Crowbar circuit
C) Analog to digital converter
D) Digital to analog converter
17. A simple device that can convert mechanical motion to pneumatic
pressure levels is the __________________.
A) Pump
B) Generator
C) Nozzle?flapper system
D) Wheatstone bridge
18. Control valve sizing is done by choosing the valve size with the
appropriate ___________________.
A) Metallic characteristics
B) Valve flow coefficient
C) Flange
D) Orifice plate
19. A process that can be controlled by reading on or off conditions and
responding with other on or off conditions is called a _____________ state
system.

4. A) Analog
B) Continuous control
C) Discrete
D) PID
20. Alarm conditions can best be described
by_________________________.
A) Loop equations
B) Simultaneous equations
C) Boolean equations
D) None of the above
21. Programmable logic controllers can replace electromagnetic relays in
control systems.
A) True
B) False
22. The below schematic symbol is a _________________.
A) Normally closed limit switch
B) A normally open momentary pushbutton
C) A pressure switch
D) A level switch
E) A normally closed temperature switch
23. Could the below circuit be used to control a motor starter?
A) Yes
B) No
24. The process the PLC uses to read the inputs, solve the ladder logic, and
drive the outputs is the PLC_____________ for that specific application.
A) State table
B) Memory
C) Throughput time
D) Application
25. In order for the PLC to interact with the process inputs and outputs the
I?O must be compatible with the input signal and output signal __________.
A) Capacity
B) Voltages and currents
C) Scan time
D) Memory

5. 26. Sensor resistance varies from 25 to 1.5 kΩ as a variable changes from
cmin to cmax. Design a signal-conditioning system that provides an output
varying from –2 to +2 V as the variable changes from min to max. Power
dissipation in the sensor must be kept below 2.5 mW.
Solution:
The circuit could be implemented as under:
27. A 10-bit unipolar ADC with a reference of 5.00 F and a 44-μs conversion
time will be used to collect data on time constant measurement. Thus, the
input will be of the form V (t) = 4(1− et/τ ) . What is the minimum value of τ for
which reliable data samples can be taken if no Sample-and-Hold circuit is
used?
Solution;
28. A type K thermocouple with a 0°C reference will be used to measure
temperature between 200°C and 350°C . Devise a system that will convert
this temperature range into an 8-bit digital word with conversion from 00H to
01H at 200°C and from FEH to FFH at 350°C . An ADC is available with a
2.500-V internal reference. At 200°C a type K TC produces 8.13 mV. At 350
°C a type K TC produces 14.29 mV.
29. A strain gauge has a and a nominal resistance of 120 Ω . Calculate the
resistance change resulting from a strain of 144μin / in .
Solution:
30. Consider the phototransistor with IV curves below left and used in the
circuit below right. Calculate the output voltage when the light intensity is
equal to 20 W /m2 .
Solution:
31. A 4- to 20-mA control signal is loaded by a 100-Ω resistor and must
produce a 20- to 40-V motor drive signal. Develop the equation relating the
input current to the output voltage. Implement the equation if a power amplifier
is available that can output 0 to 100V and has a gain of 10.
32. It is desired to control the batch below process with a programmable logic
controller. All of the sensors and control devices are discrete devices
operating at 120 vac. List which signals are inputs and which are outputs.

6. What is the complete I/O count that should be specified for the programmable
logic controller? How would you recommend starting and stopping this
system?
33. Consider the drawing below and answer each of the following questions
with one or more complete sentences:
a. What kind of drawing is represented above?
b. What is driving the setpoint for the pressure of ingredient “A”?
c. What kind of signal is driving the setpoint for ingredient “A”?
d. What is controlling the flow of ingredient “B”?
e. What is driving the setpoint of the flow of product leaving at “C”?
34. Consider the logic diagram below. Convert this logic diagram to ladder
logic.