COMPRE REVIEWERS Flashcards
Response of a system to a sinusoidal input is called
___________ response.
(a) impulse
(b) unit step
(c) frequency
(d) none of these
(c) frequency
Dead zone is the
(a) same as time constant.
(b) same as transportation lag.
(c) maximum change in the variable that does
not change the reading of the instrument.
(d) none of these
(c) maximum change in the variable that does
not change the reading of the instrument
When the damping co-efficient is unity, the system is
(a) overdamped.
(b) critically damped.
(c) underdamped.
(d) highly fluctuating
(b) critically damped
Pick out the first order system from among the
following.
(a) Damped vibrator.
(b) Mercury in glass thermometer kept in boiling
water.
(c) Interacting system of two tanks in series.
(d) Non-interacting system of two tanks in series.
(b) Mercury in glass thermometer kept in boiling
water.
For two non-interacting first order systems connected
in series, the overall transfer function is the
__________ of the individual transfer functions.
(a) product
(b) ratio
(c) sum
(d) difference
(a) product
Transfer function of a first order system is
(a) 1 / Ts+1
(b) 1 / Ts
(c) s / Ts+1
(d) none of these
(a) 1 / Ts+1
Response of a linear control system for a change in set
point is called
(a) frequency response
(b) transient response
(c) servo problem
(d) regulator problem
(c) servo problem
A stable system is the one
(a) for which the output response is bounded for all bounded input.
(b) which exhibits an unbounded response to a bounded input
(c) which satisfies the conditions for a servo
problem.
(d) none of these.
(a) for which the output response is bounded for all bounded input.
If response of a control system is to be free of offset
and oscillation, the most suitable controller is
(a) proportional controller.
(b) proportional-derivative (PD) controller.
(c) proportional-integral (PI) controller.
(d) proportional-integral-derivative (PID) controller.
(d) proportional-integral-derivative (PID) controller
For measuring the temperature of a red hot furnace,
which is the most suitable instrument?
(a) Platinum resistance thermometer
(b) Thermocouple
(c) Optical pyrometer
(d) Bimetallic thermometer
(c) Optical pyrometer
A negative gain margin expressed in decibels means
a/an ____________ system.
(a) stable
(b) unstable
(c) critically damped
(d) none of these
(b) unstable
Degree to which an instrument indicates the changes in measured variable without dynamic error is called its
(a) speed of response
(b) reproducibility
(c) fidelity
(d) static characteristics
(d) static characteristics
Degree to which an instrument indicates the changes in measured variable without dynamic error is called its
(a) speed of response
(b) reproducibility
(c) fidelity
(d) static characteristics
(c) fidelity
Which of the following controllers has maximum
offset?
(a) P-controller
(b) P-I controller
(c) P-D controller
(d) P-I-D controller
(a) P-controller
Cascade control means
(a) feed forward control.
(b) more than one feed-back loop.
(c) on-off control.
(d) one feed-back loop
(b) more than one feed-back loop.
In an exothermic chemical reactor, the manipulated variable is the flow rate of
(a) coolant
(b) reactants
(c) product
(d) none of these
(a) coolant
E.m.f. generated by thermocouples is of the order of
(a) millivolts
(b) microvolts
(c) volts
(d) kilovolts
(a) millivolts
Instrumentation in a plant offers the advantage of
(a) greater safety of operation
(b) better quality of product
(c) greater operation economy
(d) all (a), (b) and (c)
(d) all (a), (b) and (c)
Laplace transform method is used for _______ behavior
(a) linear
(b) non-linear
(c) both (a) and (b)
(d) neither (a) nor (b)
(a) linear
A controller action in which, there is a continuous
linear relation between value of the controlled
variable and rate of change of controlled output signal
is called the _____________ action.
(a) proportional
(b) integral
(c) derivative
(d) none of these
(c) derivative
Steady state deviation resulting from a change in the value of the load variable is called the
(a) offset
(b) error ratio
(c) deviation
(d) static error
(a) offset
Time required for the output of a first order system to change from a given value to within 36.8% of the final
value, when a step change of input is made, is called the
(a) time constant
(b) settling time
(c) rise time
(d) derivative time
(a) time constant
A controller action in which there is a continuous relation between value of the controlled variable and
the value of the output signal of the controller is called the action.
(a) proportional
(b) derivative
(c) integral
(d) none of these
(a) proportional
On-off control
(a) fully opens the final control element when the measured variable is below the set point.
(b) fully closes the final control element when the measured variable is above the set point.
(c) is a two position (fully open or fully closed)
control adequate to control a process with slow reaction rate and minimum dead time or transfer lag.
(d) none of these
(c) is a two position (fully open or fully closed)
control adequate to control a process with slow reaction rate and minimum dead time or transfer lag
Standard air pressure range for pneumatic controller
is between _________ psi.
(a) 0 to 12
(b) 5 to 25
(c) 4 to 30
(d) 3 to 15
(d) 3 to 15
On-off control is a special case of ___________
control.
(a) proportional (P)
(b) proportional-In tegral-eriva tive(PID)
(c) proportional-derivative (PD)
(d) proportional-integral (PI)
(a) proportional (P)
Which one is a controlled variable in a heat
exchanger?
(a) Flow rate of cooling fluid
(b) Outlet temperature of cooling fluid
(c) Inlet temperature of cooling fluid
(d) Inlet temperature of heating fluid
(b) Outlet temperature of cooling fluid
Thermocouple in a temperature recorder is an example of ____________ element.
(a) functioning
(b) manipulating
(c) secondary
(d) primary
(d) primary
Laplace transform of impulse input of magnitude ‘A’ is
(a) A
(b) A^2
(c) 1/A
(d) 0
(a) A
Laplacian form of measuring lag is
(a) e^-LS
(b) e^LS
(c) e^-L^2s
(d) e^L^2s
where, L = Lag time
(a) e^-LS
Laplace transform of unit step change is
(a) 1
(b) 1/s
(c) 1/s^2
(d) 0
(b) 1/s
Which of the following controllers is used for level control in industries?
(a) P
(b) PI
(c) PD
(d) PID
(a) P
Derivative control is used
(a) alone
(b) along with proportional control
(c) along with integral control
(d) none of these
(b) along with proportional control
If, L(Y) = Laplace transform of output variable and
L(X) = Laplace transform of input variable, then
transfer function is defined as
(a) L(Y) / L(X)
(b) L(X) / L(Y)
(c) L(X) L(Y)
(d) L(X) – L(Y)
(a) L(Y) / L(X)
The time constant of a first order system is defined as
the time for system to reach following a step input
change ______ % of its final value.
(a) 63.2
(b) 99.8
(c) 85.4
(d) 18.8
(a) 63.2
The mechanism which changes the value of the
manipulated variable in response to the output signal from the control unit is called the
(a) final control element
(b) on-off control
(c) floating control action
(d) none of these
(a) final control element
Open loop gain is obtained by substituting
(a) s = 0
(b) s = infinity
(c) s = 1
(d) s= -1
(a) s = 0
Describing functions can be used up to _______
variables.
(a) one
(b) three
(c) five
(d) any number of
(d) any number of
Temperature in °F and °C are the same at
(a) 320°
(b) 0°
(c) 212°
(d) -40°
(d) -40°
A non-linear system will have ______ steady state
values.
(a) 2
(b) 3
(c) 5
(d) many (>1)
(d) many (>1)
______________ input increases linearly with time.
(a) Step
(b) Ramp
(c) Impulse
(d) Sinusoidal
(b) Ramp
Characteristic equation is the denominator of
_________ loop transfer function.
(a) open
(b) closed
(c) both (a)and (b)
(d) neither (a) nor (b)
(b) closed
The function of a transducer is to
(a) modify the input signal.
(b) amplify the input signal.
(c) convert the primary signal into a more useful
quantity, usually an electric impulse.
(d) codify/decodify the input signal.
(c) convert the primary signal into a more useful
quantity, usually an electric impulse.
On-off control which is a special case of proportional
control, has a band width of about _______ percent.
(a) 100
(b) 75
(c) 25
(d) 0
(d) 0
A proportional controller has a proportional band of 380%. The gain will be
(a) 7.60
(b) 0.263
(c) 3.80
(d) 0.132
(b) 0.263
Automatic controllers operate on the difference
between set point and measurement, which is called:
(a) feedback
(b) bias
(c) error
(d) offset.
(c) error
Response due to a sinusoidal input is:
(a) exponentially increasing
(b) exponentially decreasing
(c) sinusoidal
(d) an impulse function
(c) sinusoidal
The response of derivative action to a step input is a
(a) step
(b) sinewave
(c) ramp
(d) spike
(d) spike
Transfer function is defined as the ratio of Laplace transforms of
(a) output deviation variable to input deviation
variable
(b) controlled variable deviation to forcing function
(c) controller output deviation to disturbance
deviation
(d) none of these
(a) output deviation variable to input deviation
variable
Which of the following is an undesirable dynamic
characteristic of an instrument ?
(a) Reproducibility
(b) Dead zone
(c) Time lag
(d) Static error
(c) Time lag
The unit of ‘time constant’ of a system is the same as
that of
(a) velocity
(b) time
(c) (time)-1
(d) none of these
(b) time
Transfer function of a system is used to calculate which of the following ?
(a) The order of the system
(b) The time constant
(c) The output for any given input
(d) The steady state gain
(c) The output for any given input
A controller, essentially, is a
(a) sensor
(b) clipper
(c) comparator
(d) amplifier
(c) comparator
The transient response of a system is mainly due to
(a) inertia forces
(b) internal forces
(c) stored energy
(d) friction
(c) stored energy
A signal other than the reference input that tends to
affect the value of controlled variable is known as
(a) disturbance
(b) command
(c) control element
(d) reference input
(a) disturbance
Which of the following operates on an open loop
control system?
(a) Hot water dispenser
(b) Toaster
(c) Flat iron
(d) None of these
(b) Toaster
A thermometer having a time constant of 10 seconds
is initially at 30°C. It is suddenly immersed in a bath
maintained at 100°C. How long will it take for the
thermometer reading to reach 90°C?
(a) 19.5 seconds
(b) 10.5 seconds
(c) 15.9 seconds
(d) 25.0 seconds
(a) 19.5 seconds
The simplest mode. of control which is characteristic of a two-position control
commonly utilized in a thermostat for controlling the temperature of heaters, air conditioners, refrigerators,. etc.
a. proportional control
c. on-off control
b. derivative control
d. programmable logic control
c. on-off control
It is a control system in which the control action is independent of the output.
a. closed-loop system
c. open-loop system
b. feedback control system
d. cascade control system
c. open-loop system
An arrangement of physical components connected or related in such a manner as to
command, direct or regulate itself or another system.
a. stimulus
c. control system
b. unit process
d. unit operation
c. control system
It is the actual response obtained from the control system. It may or may not be equal
to the specified response implied by the input.
a. input
b. output
c. answer
d. result
b. output
The response of two tanks in series is
a. overdamped
c. critically damped
b. underdamped
d. oscillating
a. overdamped
A control system in which the control action is somehow dependent on the output.
a. closed-loop control system
c. feedforward control system
b. open-loop control system
d. deadtime compensator
a. closed-loop control system
A property of a closed-loop system which- permits the output (or some other controlled
variable) to be compared with the input to the system (or the input to some other
internally situated component or subsystem) so that the appropriate control action may
be formed as some fraction of the output and input.
a. feedback control system
c. continuous time
b. control system
d. bandwidth
d. bandwidth
A signal dependent on continuum of values of the independent variable.
a. continuous time signal c. AM signal
b. discrete time signal
d. SOS signal
a. continuous time signal
It is used to convert one signal or energy form into another.
a. transducer
c. detector
b. amplifier
d. resistor
a. transducer
The part of the deviation of the response which approaches zero as ·time approaches
infinity.
a. steady state response c. transient response
b. output
d. frequency response
a. steady state response
The integral of a unit step function is also known as
a. unit ramp function
c. unit impulse function
b. sinusoidal function
d. transcendental function
a. unit ramp function
A control structure with two feedback controllers with the output of the primary controller changing the set-point of the secondary controller whose output goes to the
final controller.
a. feedforward control
c. cascade control
b. ratio control
d. override control
c. cascade control
A sensor usually made of a semiconductor that utilizes the effect of temperature on the
resistance to current is called a
a. thermocouple
b. thermistor
c. resistor
d. capacitor
b. thermistor
If a step function is applied to the input of a system and the output remains below
a certain level for all time~ is the system necessarily stable?
a. true
b. false
c. cannot be determined
b. false
A proportional controller exhibits a large offset. This offset can be eliminated without
altering the proportional constant Kc by
a. adding another proportional control
c. adding an integral control
b. adding an on-off control
d. adding a derivative control
c. adding an integral control
A PI controller of a first order process is subjected to a unit step input. If the integral
constant is fixed, decreasing the proportional gain will
a. increase the overshoot c. decrease the overshoot
b. increase the oscillation d. decrease the offset
a. increase the overshoot
The integral of a Dirac function is a
a. ramp function
b. step function
c. impulse function
d. pulse function
b. step function
A PID controlled process has a highly oscillating response. The process can be stabilized by
a. increasing proportional gain
c. increasing derivative time constant
b. decreasing proportional gain
d. decreasing derivative time constant
b. decreasing proportional gain
A PI controller of a first order process is subjected to a unit step input. If the integral
constant is fixed, increasing the proportional gain will
a. increase the overshoot c. decrease the offset
b. increase the oscillation d. decrease the overshoot
d. decrease the overshoot
