CAMBRIAN COLLEGE
ELECTRICAL ENGINEERING
TECHNOLOGY
INSTRUMENTATION (III)
INT_3505
TEST #1
Student Name:_______________________
Student ID#:________________________
1
CRN #:___________________________
Q1: (3 marks)
Explain the difference system capacity and system capacitance?
Q2: (4 marks)
Give names for eight process variables:
1. 2. 3. 4.
5. 6. 7. 8.
Q3 : ( 2 marks)
In your home, if a light automatically turns on and off by the use of a timer, is this a form of
on / off control?
a) Yes
b) No
Q4: ( 3 marks)
Which of the listed process variables are suitable for on / off control?
a. Flow of air through heating duct
work
b. Pressure in an air conditioning
system
c. Temperature of a gas stove
d. Toilet tank level control
e. home temperature
2
Q5: ( 2 marks)
The possible adjustments found on On / Off control systems can include
a. hysteresis compensation
b. deadband adjustment
c. selection between additive and subtractive
deadband
d. setpoint adjustment
Q6: ( 4 marks)
Why is ON/OFF control so popular. Choose ALL the correct answers
a. Inexpensive
b. Works well on systems with large system
capacitance.
c. Works well on systems with large system capacity.
d. Easy to install
e. Easy to troubleshoot
f. Better accuracy that other types
g. Always used in low voltage applications
Q7: ( 2 marks)
Where is on off control not suitable?
a. sump pump level
control
b. flow rate of fluids
c. pressure control
d. temperature control
Q8: ( 2 marks)
You open a temperature switch and you examine the switch mechanism. It has 3 terminal
3
screws. This means it's a:
a. SPDT
b. SPST
c.
DPDT
d. DPST
Q9: ( 2 marks)
On off control is best described by:
a. Traffic lights
b. Alarm clock used each
morning
c. PRV diaphragm operation
d. Fridge cooling system
e. Remote TV controller
Q10: ( 3 marks)
When ordering a replacement temperature switch what items are required. (Choose ALL that
apply).
a. temperature range
b. deadband
c. contact ratings
d. switch type
e. type of temperature sensor, ie)
bimetal
Q11: ( 3 marks)
On / Off control is widely used because: ( choose all correct answers)
a. It is inexpensive as compared to other systems due to the system needing few parts
b. The process control is close enough for most applications
c. The deadband can always be adjusted if it is too wide to get better control
d. Many applications have a large system capacitance that works well with this type of
control
e. The setpoint, in most systems, doesn't have to be exact to accomplish the control
required
4
Q12: (2 marks)
Short cycling is a term used to describe:
a. the number of ON/OFF conditions in a period of time
b. the ON time of a heating element
c. the number of times a control goes from ON to OFF and back
ON
d. the surge current in solenoid valves
e. the ratio of ON time to the OFF time for the device
Q13: ( 2 marks)
A 3 way solenoid valve in an ON/OFF control loop is used with pneumatically operated valve
to:
a. vent air from the actuator
b. reverse the process fluid flow
c. activate an alarm
d. reverse the action of the pneumatic
valve
Q14: ( 4 marks)
One of the objectives of a control system is environment protection. Explain how that is
achieved.
Q15: ( 5 marks)
State five control systems objectives other than that mentioned in Q14:
1.
5
2.
3.
4.
5.
Q16: (6 marks)
Draw the P & I diagram for the following process:
“Wild out” controlled input of a pressure tank using a pressure switch and a solenoid valve.
Q17: (4 marks)
For which process variables the ON/OFF control is mostly used? Explain why.
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Q18: (4 marks)
The following applies to an ON/OFF pressure control loop…
* It has a controlled feed ( wild output)
* The process variable has greatly exceeded the set point
*The final control element is NC, rated for 120 Vac and is energized
*The final control element is in the open position.
Determine the possible fault(s).
Q19: (5 marks)
Any closed loop control system can be represented by four blocks as shown below. Put an
arrow on the dotted lines to show the flow of information and give the name of each block i,e:
” What does each block represent in the closed loop control system”.
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Q20: (5 marks)
In Lab#1, you controlled pressure inside a tank, fill out the blocks in the following figure that
represents a closed loop pressure control system, and don’t forget the arrows on the dotted
lines.
Q21: (3 marks)
What is the difference between a closed loop and an open loop control system?
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Q22: (5 marks)
From the above figure fill out the following block diagram that represents a closed loop
control system.
Q23: (4 marks)
EX#1: ( 4 marks)
For the P & I diagram below, draw the electrical wiring diagram. Use the terminal block
given for connections.
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Q24: (6 marks)
a) Is the control loop in the following system a closed or open loop?
Answer:______________________
b) From the above system fill out the following four control blocks.
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Q#2: (6 marks)
A pneumatic differential pressure transmitter has a calibrated range of -100 to
+100 inches of water column (” W.C.), and its output signal range is 3 to 15 PSI.
Complete the following table of values for this transmitter, assuming perfect
calibration (zero error).
Input Pressure (“WC) Percent of span (%) Output signal (PSI)
0
-30
8
13
65
10
Show one example of your calculations for each column.
Input Pressure (“WC)
11
Percent of span %
Output signal (PSI)
12
