Pneumatic Signal , Pneumatic Systems, Pneumatic Control Mechanisms Questions and Answers

 Pneumatic Signal , Pneumatic Systems, Pneumatic Control Mechanisms Questions and Answers

Pneumatic Signal 

1. The standard range for pneumatically transmitted signals is
a) 3-15 psig
b) 5-20 psig
c) 1-10 psig
d) 4-20 psig
Answer: 3-15 psig
 2.  pneumatic signal are the signals produced by changing the air pressure in the signal pipe in proportion to the measured change in a process variable. 
a) True
b) False
Answer: True

Pneumatic Systems

1. Hydraulic and pneumatic circuits
a) Perform the same way for all functions
b) Perform differently for all functions
c) Perform the same with some exceptions
d) Does not perform all the functions
Answer: Perform the same with some exceptions
2. Fluid power circuits use schematic drawings to
a) Simplify component function details
b) Make it so only trained persons can understand the functions
c) Make the drawing look impressive
d) Make untrained person to understand
Answer: Simplify component function details
3. The most common hydraulic fluid is
a) Mineral oil
b) Synthetic fluid
c) Water
d) Gel
Answer: Water
4. Pneumatic systems usually do not exceed
a) 1 hp
b) 1 to 2 hp
c) 2 to 3 hp
d) 4 to 5 hp
Answer: 1 hp
5. Series circuits work on both hydraulic and pneumatic actuators.
a) True
b) False
Answer: False
6. Most hydraulic circuits
a) Operate from a central hydraulic power unit
b) Use air-over-oil power units
c) Have a dedicated power unit
d) Does not have dedicated power unit
Answer: Operate from a central hydraulic power unit
7. The lubricator in a pneumatic circuit is the
a) First element in line
b) Second element in line
c) Last element in line
d) Third element in line
Answer: Last element in line
8. When comparing first cost of hydraulic systems to pneumatic systems, generally they are
a) More expensive to purchase
b) Less expensive to purchase
c) Cost is same
d) Cost is not required
Answer: Less expensive to purchase
9. When comparing operating cost of hydraulic systems to pneumatic systems, generally they are.
a) More expensive to operate
b) Less expensive to operate
c) Cost is same to operate
d) Cost is not required
Answer: Less expensive to operate
10. A pneumatic symbol is
a) Different from a hydraulic symbol used for the same function
b) The same as a hydraulic symbol used for the same function
c) Not to be compared to a hydraulic symbol used for the same function
d) None of the mentioned
Answer: Different from a hydraulic symbol used for the same function
11. In pneumatic systems time lags are obtained by
a) Pneumatic-electric elements
b) Making the air to fill a volume after passing  through a restriction
c) Elongating the path of air
d) None of the mentioned
Answer: Making the air to fill a volume after passing  through a restriction
12. In pneumatic control systems compensation is provided by which of the following ?
a) Bimetal strips
b) Extension tubes
c) Flapper nozzle mechanism
d) Restriction volume combinations
Answer: Flapper nozzle mechanism
13. In pneumatic control systems the control panel used as final control element converts
a) Pressure signal to electric signal
b) Pressure signal to position change
c) Electric signals to be sure signal
d) Position change to pressure signal
Answer: Pressure signal to position change
14. The compressed air, in pneumatic control systems, is not
a) Lubricatedated
b) Filtered
c) Regulated
d) All of the above
Answer: Lubricated
15. A pneumatic amplifie
a) Amplifiers flow
b) Amplifiers differential pressure
c) Amplifiers change in air volume
d) All of the above
Answer: Amplifiers differential pressure
16. In pneumatic instrumentation systems the pressure of compressed air used is around
a) 1 bar
b) 2.5 bar
c) 5.5 bar
d) 3.4 bar
Answer: 1 bar
17. In pneumatic systems the medium used is
a) Air
b) Liquid
c) Hydrogen
d) Oil
Answer: Air
18. In pneumatic systems a restriction-volume combination is equivalent to
a) R.L. circuit
b) R.C. circuit
c) Rectifier
d) Resonant circuit
Answer: R.C. circuit
19. _____ cannot be the final control element
a) Potentiometer
b) Electro-pneumatic converter
c) Servomotor
d) All of the above
Answer: Potentiometer
20. In pneumatic-electrical analogy, the electrical resistance is analogous to
a) Field helical tube
b) Volume of air
c) Restriction to flow
d) None of the above
Answer: Restriction to flow

Pneumatic Control Mechanisms

1. If the distance between loop components in the all pneumatic control system must be increased it will require
a) A pneumatic volume booster
b) Larger sized tubing
c) Smaller sized tubing
d) Conversion to an electrical signal
Answer: Conversion to an electrical signal
2. With a proportional-plus-integral controller, a sustained error will result in
a) Windup
b) A fixed offset
c) A temporary narrowing of the proportional band
d) A delay in the process
Answer: Windup
3. For fail-safe action the control valve should, upon energy (air) failure
a) Open
b) Close
c) Move in such direction as to make the process nonhazardous
d) Stay in its previous position
Answer: Move in such direction as to make the process nonhazardous
4. By locating the derivative function in the input measurement circuit, which of the following advantages can be realized?
a) Smooth bump-less transfer
b) No derivative bump with a set-point change
c) No proportional response to a set-point change
d) Integral adjustment is isolated from response
Answer: No derivative bump with a set-point change
5. The advantage of adding derivative to a controller is always
a) Increased stability
b) The ability to overcome a big pure dead time lag
c) The ability to react more quickly to measurement change
d) A decrease in the pure dead time of the process
Answer: The ability to react more quickly to measurement change
6. If the closed-loop control system has too much gain, it will cycle. The only loop component that has conveniently adjustable gain is the
a) Measuring transmitter
b) Valve operator
c) Process
d) Controller
Answer: Controller
7. A process is to be controlled using an all pneumatic system. The maximum distance between loop components will be
a) 1,000 feet
b) 500 feet
c) 200 feet
d) 20 feet
Answer: 200 feet
8. If the span of a measuring transmitter in a control system is made one-half of its value, the proportional-band adjustment in the controller must be -to maintain the same quality of control.
a) Cut in half
b) Doubled
c) Squared
d) Narrowed
Answer: Doubled
9. Pneumatic signals travel through the signal tubing at
a) 100 feet per second
b) Approximately the speed of sound
c) A rate that depends on tubing size
d) Approximately the speed of light
Answer: Approximately the speed of sound
10. In a proportional-only controller, if the measurement equals the set point the output will equal the bias. True or False ?
a) True
b) False
Answer: True
11. In an integral controller, the rate of change of the output is proportional to the error. True or False ?
a) True
b) False
Answer: True
12. The larger the number on the integral dial the greater the effect of the integral action. True or False ?
a) True
b) False
Answer: False
13. In a batch operation, if a controller has wound up, it is quite possible that the valve may stay in an extreme position until the measurement actually goes beyond the set point before the valve begins to change its position. True or False ?
a) True
b) False
Answer: True
14. What some manufacturers call rate others call derivative. True or False ?
a) True
b) False
Answer: True
15. If proportional-plus-integral control is good, the addition of derivative
a) Will anticipate changes and speed up corrections
b) Will always improve control
c) Will make the controller adjustments easier to accomplish
d) May create stability problems in some system
Answer: May create stability problems in some system
16. In a process controlled by a proportional-plus-integral controller, the measurement was at the set point and the output was 9 psi (60 kPa). The measurement then quickly decreased to a certain value below the set point and leveled out there. The output responded by changing to 8 psi (55 kPa). As time progresses, what would you expect from the output pressure?
a) Increase to 9 psi (60 kPa) to bring the measurement back to the set point
b) Remain at 8 psi (55 kPa) as long as the measurement stays where it is.
c) Decrease and continue to decrease to 3 psi (20 kPa).
d) Continue to decrease until the measurement reaches the set point, or if it does not return to the set point, decrease to 0 psi.
Answer: Continue to decrease until the measurement reaches the set point, or if it does not return to the set point, decrease to 0 psi.
17. Adjusting the controller for optimum performance
a) Is not required, because it adjusts itself
b) Requires a special tool
c) Is usually done by trial and error
d) Always requires a very involved mathematical analysis of the process
Answer: Is usually done by trial and error
18. The range of the temperature measuring system used in conjunction with a Model 130 proportional-only controller is 0 to 150°f (66°C). The output is 9 psi (60 kPa) when the set point and indicator are both at 75°f (24°C). If proportional band is 200 percent, what is the output when the measurement is 150°f (66°C)?
a) 9 psi (60 kPa)
b) 3 psi (20 kPa)
c) 12 psi (83 kPa)
d) 15 psi (100 kPa)
Answer: 12 psi (83 kPa)
19. The integral dial in a pneumatic controller is calibrated in
a) Minutes or repeats
b) Integral units
c) Gain
d) Percentage
e) Offset
Answer: Minutes or repeats

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