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# Multiple choice question for engineering

## Set 1

1. A single channel data system consists of a signal conditioner, A/D converter and a buffer.
a) True
b) False

Answer: a [Reason:] The single channel data acquisition system consists of a signal conditioner, an analog to digital converter and a buffer circuitry.

2. A/D conversion rate is __________
a) variable
b) predefined
c) zero
d) constant

Answer: b [Reason:] In a single channel data acquisition system, the conversion rate of an analog to digital converter is predefined. A/D converter performs the conversions at a pre-determined rate.

3. The buffer output is ________
a) analog
b) zero
c) digital
d) mixed mode

Answer: c [Reason:] In a single channel data acquisition system, the output of the buffer circuitry is digital in nature. It is stored in a digital computer or a storage device or sometimes even a printer.

4. The best example for a single channel data acquisition system is
a) CPM
b) BPM
c) APM
d) DPM

Answer: d [Reason:] A digital panel meter usually abbreviated as DPM is the best example for a single channel data acquisition system.

5. Digital outputs are obtained from
a) A/D converter
b) D/A converter
c) Oscilloscope
d) Voltage source

Answer: a [Reason:] An analog to digital converter provides digital outputs. The A/D converters are designed in such a way that they accept external commands in order to convert and hold the operations.

6. A/D converters can’t be used for low frequency ranges.
a) True
b) False

Answer: b [Reason:] Analog to digital converters based on the dual slope techniques are usually used in the conversion of low frequency data coming from the thermocouples.

7. Which technique is most widely used in the single channel data acquisition system?
a) Counter type approximation
b) Flash approximation
c) Successive approximation
d) Delta Sigma approximation

Answer: c [Reason:] The successive approximation technique is most widely used in a single channel data acquisition system. This is due to the fact that it has a high value of resolution and a high speed.

8. What is pre-amplification?
a) reducing the magnitude of a signal
b) making the magnitude of a signal zero
c) reducing the noise
d) boosting the signal

Answer: d [Reason:] To match the input needs, the level of an input signal is boosted. This is done as the magnitude of the input signal is sometimes very low. This is known as pre-amplification.

9. How can the input be isolated from the system?
a) using optocouplers
b) using op-amps
c) using a capacitor
d) using rectifiers

Answer: a [Reason:] By making use of an optocoupler, we can isolate the input signal from the system. Before processing the data, pre-amplifiers are fitted with active filters so as to eliminate the noise and boost the signal.

## Set 2

1. At very low frequencies in a AC bridge, the source is _________
a) power line
b) e.m.f
c) galvanometer
d) tuned circuit

Answer: a [Reason:] Galvanometer is used for detecting the balance condition. The power line acts as a source of supply for bridge measurements in an AC bridge circuit at very low frequencies.

2. At high frequencies in a AC bridge, the source is _______
a) tuned amplifiers
b) oscillators
c) vibration galvanometer
d) high voltage source

Answer: b [Reason:] Tuned amplifiers are used as a source of voltage in AC bridges. Electronic oscillators are used as a source of supply for bridge measurements in an AC bridge circuit at high frequencies.

3. The frequency range of a typical oscillator is _______
a) 1 Hz to 50 Hz
b) 1 kHz to 100 KHz
c) 40 Hz to 125 kHz
d) 1 MHz to 150 MHz

Answer: c [Reason:] An oscillator has a frequency range slightly above the audio frequency. A typical oscillator has a frequency range of 40 Hz to 125 kHz.

4. The power output for a typical oscillator is _______
a) 1 kW
b) 1 MW
c) 1 mW
d) 7 W

Answer: d [Reason:] Oscillator usually has a low power output. A typical oscillator has a power output of around 7 W.

5. The output waveform in a oscillator is _______
a) sinusoidal
b) cosinusoidal
c) tangential
d) logarithmic

Answer: a [Reason:] AC supply is generally in the form of sinusoidal signal. In an electronic oscillator, output waveform is very close to sinusoidal.

6. The output frequency of an oscillator is _______
a) unstable and fixed
b) stable and adjustable
c) stable and fixed
d) unstable and variable

Answer: b [Reason:] In an electronic oscillator, the output frequency is stable. It can be determined accurately and is also adjustable.

7. The output power of an oscillator is not enough to drive power circuits.
a) True
b) False

Answer: b [Reason:] Power circuits generally require a low output in order to function. An electronic oscillator provides sufficient output power to drive power circuits.

8. Tuned amplifiers can be set to _______
a) low frequencies
b) high frequencies
c) any frequency
d) audio frequencies

Answer: c [Reason:] Tuning refers to varying a parameter. Tuned amplifier circuits can be set to any desired frequency.

9. Tuned amplifier circuits respond to broad bandwidth at bridge frequency.
a) True
b) False

Answer: b [Reason:] Amplifiers can be used to detect the balance condition in AC bridges. Tuned amplifier circuits consist of transistors that respond to a narrow bandwidth at the bridge frequency.

## Set 3

1. Strain gauge measurement involves __________
a) Wheatstone bridge
b) Kelvin bridge
c) De Sauty’s bridge
d) Anderson bridge

Answer: a [Reason:] Strain gauge makes use of the practical form of Wheatstone’s bridge to measure the strain developed by an element.

2. Load cell is used for the measurement of _______
a) area
b) force
c) mass
d) length

Answer: b [Reason:] The load cell is used in a semiconductor strain gauge for the measurement of force. Load cells measure the deformation that is produced by force or weight.

3. Strain is a _______
a) fractional change in volume
b) fractional change in area
c) fractional change in length
d) fractional change in height

Answer: c [Reason:] Strain is defined as the fractional change in length of a body. A change in resistance of the element is reflected in the form of strain of the gauge as well as the element.

4. Semiconductor strain gauge uses _______
a) rectifier circuitry
b) power electronics circuitry
c) ordinary bridge circuit
d) bridge circuit with temperature compensation

Answer: d [Reason:] The semiconductor strain gauge makes use of a Wheatstone practical bridge circuit along with temperature compensation. Output is made linear as the resistance characteristics with respect to strain are non-linear.

5. A semiconductor strain gauge consists of how many dummy gauges?
a) 2
b) 4
c) 6
d) 10

Answer: a [Reason:] The semiconductor strain gauge consists of two dummy gauges in the form of two arms of the Wheatstone bridge circuit. Dummy gauges are used for temperature compensation.

6. Metals in strain gauge construction have _______
a) non-linear temperature coefficient
b) linear temperature coefficient
c) tangential temperature coefficient
d) exponential temperature coefficient

Answer: b [Reason:] The metals used in a strain gauge construction have a linear temperature coefficient. A change in the temperature affects the resistance and varies the value of strain.

7. A Wheatstone bridge has _______
a) low sensitivity
b) zero sensitivity
c) high sensitivity
d) infinite sensitivity

Answer: c [Reason:] A Wheatstone bridge circuit has a high sensitivity for detecting very small variation in the values of resistance. We can connect the strain gauge in one of the arms of a Wheatstone bridge and measure the strain in terms of variation in resistance.

8. Load cells are calibrated such that _______
a) force varies inversely with resistance
b) force varies as the square of resistance
c) force remains constant with resistance
d) force varies directly with resistance

Answer: d [Reason:] The load cells in a semiconductor strain gauge are calibrated in such a way that the force or weight varies directly as the resistance. The strain gauge is arranged in the form of a bridge.

9. Load cell is sensitive to minute strains.
a) True
b) False

Answer: a [Reason:] A load cell responds to very minute variation in the value of strain. It is sensitive to high values of load.

10. Mass of only about 20 kg can be measured by a load cell.
a) True
b) False

Answer: b [Reason:] Using a load cell a mass or weight of the order of 20 kg to 20,000 kg can be measured. By making use of appropriate load cells we can measure forces as high as 5 MN.

## Set 4

1. What is a data acquisition system?
a) system used for data processing, conversion and transmission
b) accepts data as an input
c) removes noise
d) boosts the signal

Answer: a [Reason:] A data acquisition system basically is used for the processing of data. It is also used for data conversion, data transmission and storage of data.

2. A typical data acquisition system consists of __________
a) op amps
b) sensors
c) rectifiers
d) transistors

Answer: b [Reason:] Data acquisition system consists of sensors. It also consists of suitable signal conditioners, data converters, data processors, data handlers, storage and display systems.

3. The data acquisition system implies input data collection.
a) in mixed signal form
b) in analog form
c) in digital form
d) in the form of binary codes

Answer: c [Reason:] In a data acquisition system, input data is collected in the form of digital signals. The digital signals are collected in a fast, economic, reliable and accurate manner.

4. Data measurement systems are __________
a) not flexible
b) rigid
c) less flexible
d) more flexible

Answer: d [Reason:] The data acquisition system are more flexible and easily programmable nowadays as a result of development in the automation field.

5. Modern electronic instrumentation system is not complex.
a) True
b) False

Answer: a [Reason:] Inspite of significant development in the field of electronic instrumentation systems with the advent of op amps, data converters, multiplexers, microprocessors and microcontrollers, they are not complicated.

6. The data acquisition system can have any speed.
a) True
b) False

Answer: b [Reason:] A data acquisition system must acquire the required speed at the correct time. It must also use the data efficiently to detect the status of the plant.

7. A data acquisition system provides __________
a) partial communication
b) ineffective communication
c) effective communication
d) complete communication

Answer: c [Reason:] The data acquisition system must be able to provide proper human communication to minimize the unit availability and maximize the unit output at a lower cost.

8. Data acquisition system can be used in __________
a) 10 ways
b) 8 ways
c) 4 ways
d) 2 ways

Answer: d [Reason:] A data acquisition system can be used to measure and record the signals in two ways. In the first method the signal can be directly measured from electrical quantities such as a.c., d.c. voltage or current. In the second case the signal originates from transducers such as pressure transducer, thermocouple etc.

9. Data acquisition system is mainly classified into __________
a) 2 types
b) 4 types
c) 6 types
d) 8 types

Answer: a [Reason:] A data acquisition system is basically classified into two main types. They are analog and digital. While the analog data system deals with signals having analog input signals the digital data system consists of input signals in digital form.

## Set 5

1. Thermistor is a contraction _________
a) thermal resistor
b) laser resistor
c) electric resistor
d) mechanical resistor

Answer: a [Reason:] Thermistor is basically the short form of a thermal resistor. Resistors which depend on temperature are known as thermal resistors.

2. Thermistors have ________
a) positive temperature coefficient
b) negative temperature coefficient
c) zero temperature coefficient
d) infinite temperature coefficient

Answer: b [Reason:] Thermistor generally has a negative temperature coefficient of resistance. With increase in temperature, resistance of a thermistor decreases.

3. Thermistors ________
a) sense large changes in temperature
b) cannot sense any change in temperature
c) sense small changes in temperature
d) have a positive temperature coefficient of resistance

Answer: c [Reason:] Thermistors can sense very small changes in temperature. The negative temperature coefficient of thermistors can be a few percent / degree celcius change in temperature.

4. Thermistor has a resistance of ________
a) 250 ῼ to 500 kῼ
b) 50 ῼ to 10 kῼ
c) 1 ῼ to 1 kῼ
d) 100 ῼ to 100 kῼ

Answer: d [Reason:] Thermistor has a resistance range of 100 ῼ to 100 kῼ. Thermistor consists of a mixture of metallic oxides of manganese, nickel, cobalt, copper, iron and uranium.

5. Thermistors are suited for precision temperature measurements.
a) True
b) False

Answer: a [Reason:] Thermistors can be used for precision measurement of temperature, controlling g temperature and for temperature compensation due to a very large variation in resistance with temperature.

6. Change in resistance is measured using a ________
a) Anderson’s bridge
b) Wheatstone’s bridge
c) Hay’s bridge
d) Maxwell’s bridge

Answer: b [Reason:] The change in resistance in a thermistor is measured using a Wheatstone’s bridge. It is used for measurement of resistance in the range of -100°C to +200°C.

7. Thermistor material is pressed ________
a) under zero pressure
b) under low pressure
c) under high pressure
d) under low volume

Answer: c [Reason:] A thermistor material is usually pressed under high pressure to form a flat cylindrical shape. Disks and washers are placed in series or in parallel to increase the power dissipation.

8. Thermistor follows which law for small variations ________
a) Charle’s law
b) KVL
c) KCL
d) Ohm’s law

Answer: d [Reason:]s: For small changes in the values of current, voltage across a thermistor increases. It attains a peak value. Then the voltage across the thermistor decreases. As a result Ohm’s law is followed at small variations of current.

9. At small values of voltage, a thermistor ________
a) reaches peak current slowly
b) reaches peak current immediately
c) does not reaches peak current
d) reaches peak current intermediately