Q.1 Which of the following devices converts a mechanical displacement directly into an electrical voltage?
Thermocouple
LVDT (Linear Variable Differential Transformer)
Photodiode
Strain gauge
Explanation - An LVDT produces a voltage proportional to the displacement of its core without requiring external power for the sensing element, making it a displacement‑to‑voltage transducer.
Correct answer is: LVDT (Linear Variable Differential Transformer)
Q.2 What is the primary sensing element in a thermistor?
Semiconductor material
Thermoelectric couple
Metallic wire
Piezoelectric crystal
Explanation - Thermistors are made from semiconductor materials whose resistance changes sharply with temperature.
Correct answer is: Semiconductor material
Q.3 A Hall‑effect sensor is primarily used to detect:
Light intensity
Magnetic field
Pressure changes
Acoustic waves
Explanation - The Hall effect generates a voltage proportional to the magnetic flux density perpendicular to the current flow in the sensor.
Correct answer is: Magnetic field
Q.4 Which sensor type typically provides a linear output voltage proportional to the applied force?
Piezoelectric sensor
Strain gauge load cell
Capacitive pressure sensor
Thermocouple
Explanation - Strain gauge load cells change resistance proportionally to strain, and with a Wheatstone bridge they give a linear voltage output versus force.
Correct answer is: Strain gauge load cell
Q.5 The sensitivity of a sensor is defined as:
The ratio of output change to input change
The maximum measurable range
The time taken to reach steady‑state
The power consumption of the sensor
Explanation - Sensitivity = Δoutput / Δinput and indicates how much the output varies for a given change in the measurand.
Correct answer is: The ratio of output change to input change
Q.6 Which of the following is a passive transducer?
Photovoltaic cell
Thermocouple
Piezoelectric buzzer
LVDT
Explanation - A thermocouple generates a voltage directly from temperature difference without external power, making it a passive transducer.
Correct answer is: Thermocouple
Q.7 In a Wheatstone bridge used with strain gauges, what happens to the output voltage when the bridge is perfectly balanced?
It becomes maximum
It becomes zero
It oscillates
It doubles the input voltage
Explanation - A balanced Wheatstone bridge has equal ratios in both arms, resulting in zero differential voltage across the bridge output.
Correct answer is: It becomes zero
Q.8 A phototransistor differs from a photodiode mainly in that:
It requires a bias voltage
It provides current gain
It operates only in reverse‑bias
It emits light instead of detecting it
Explanation - A phototransistor amplifies the photocurrent like a transistor, giving higher output current than a photodiode for the same light intensity.
Correct answer is: It provides current gain
Q.9 Which sensor is best suited for detecting the presence of a metallic object without contact?
Capacitive proximity sensor
Inductive proximity sensor
Ultrasonic sensor
Infrared sensor
Explanation - Inductive sensors generate an electromagnetic field; the presence of metal changes the field and is detected without physical contact.
Correct answer is: Inductive proximity sensor
Q.10 The output of a piezoelectric sensor is proportional to:
Applied static force
Rate of change of force
Temperature
Magnetic field strength
Explanation - Piezoelectric materials generate charge when subjected to a changing mechanical stress; thus the output is proportional to the dynamic component (dF/dt).
Correct answer is: Rate of change of force
Q.11 Which of the following is NOT a typical source of error in sensor measurements?
Hysteresis
Linearity error
Quantization noise
Capacitance coupling
Explanation - While capacitance coupling can affect circuits, it is not classified as a standard sensor error term like hysteresis, linearity error, or quantization noise.
Correct answer is: Capacitance coupling
Q.12 A thermocouple generates voltage based on which principle?
Seebeck effect
Peltier effect
Thomson effect
Joule heating
Explanation - When two dissimilar metals are joined, a temperature difference creates a voltage (Seebeck effect).
Correct answer is: Seebeck effect
Q.13 Which type of sensor uses a change in capacitance to detect displacement?
Resistive sensor
Inductive sensor
Capacitive sensor
Piezoelectric sensor
Explanation - Capacitive sensors measure changes in capacitance caused by varying distance between two plates, which corresponds to displacement.
Correct answer is: Capacitive sensor
Q.14 For a pressure transducer with a full‑scale output of 10 V at 0–100 kPa, what output voltage corresponds to 45 kPa?
4.5 V
5.0 V
6.0 V
7.5 V
Explanation - Linearity assumed: (45/100) × 10 V = 4.5 V.
Correct answer is: 4.5 V
Q.15 Which sensor type is most appropriate for measuring high‑frequency vibrations in machinery?
Strain gauge
Piezoelectric accelerometer
Thermistor
Hall‑effect sensor
Explanation - Piezoelectric accelerometers have fast response and can accurately capture high‑frequency vibration signals.
Correct answer is: Piezoelectric accelerometer
Q.16 A sensor with a hysteresis of 2% means:
The output deviates by ±2% of full scale when input is constant
The output follows the input with a 2% lag
The output for a given input depends on whether the input is increasing or decreasing by up to 2% of the reading
The sensor drifts 2% per hour
Explanation - Hysteresis indicates the difference in output for the same input when the input is approached from opposite directions.
Correct answer is: The output for a given input depends on whether the input is increasing or decreasing by up to 2% of the reading
Q.17 Which of the following is a characteristic of an active transducer?
It requires external power to produce an output
It generates its own electrical output from the sensed energy
It only works in reverse bias
It has a linear output only for DC inputs
Explanation - Active transducers (e.g., thermocouples, photovoltaic cells) produce electrical signals directly from the physical stimulus without external excitation.
Correct answer is: It generates its own electrical output from the sensed energy
Q.18 In an ultrasonic distance sensor, the measured distance is calculated by:
Multiplying the echo time by the speed of sound and dividing by two
Dividing the echo time by the speed of sound
Adding the echo time to the speed of sound
Multiplying the echo frequency by the speed of sound
Explanation - Distance = (t × v)/2 because the sound travels to the object and back.
Correct answer is: Multiplying the echo time by the speed of sound and dividing by two
Q.19 A light‑dependent resistor (LDR) changes its resistance primarily due to:
Temperature variation
Magnetic field strength
Incident light intensity
Applied pressure
Explanation - LDRs are photoconductive; photons increase carrier density, reducing resistance with higher light intensity.
Correct answer is: Incident light intensity
Q.20 Which sensor is commonly used for measuring angular position in servomechanisms?
Linear Variable Differential Transformer (LVDT)
Rotary Encoder
Thermocouple
Capacitive displacement sensor
Explanation - Rotary encoders provide digital or analog signals proportional to angular displacement, essential for precise motion control.
Correct answer is: Rotary Encoder
Q.21 What does the term 'range' of a sensor refer to?
The maximum power the sensor can consume
The difference between the highest and lowest measurable input values
The physical size of the sensor housing
The speed at which the sensor responds
Explanation - Range defines the span of input (e.g., temperature, pressure) over which the sensor provides accurate readings.
Correct answer is: The difference between the highest and lowest measurable input values
Q.22 A temperature sensor that exhibits a linear resistance change with temperature is called:
Thermocouple
RTD (Resistance Temperature Detector)
Thermistor
Infrared sensor
Explanation - RTDs (often made of platinum) have a near‑linear resistance‑temperature relationship.
Correct answer is: RTD (Resistance Temperature Detector)
Q.23 In a voltage‑output pressure sensor, the output voltage is 0.5 V at 0 kPa and 4.5 V at 200 kPa. What is the sensor’s sensitivity (mV/kPa)?
20 mV/kPa
25 mV/kPa
30 mV/kPa
35 mV/kPa
Explanation - Sensitivity = (4.5‑0.5)V / 200kPa = 4 V / 200 kPa = 0.02 V/kPa = 20 mV/kPa.
Correct answer is: 20 mV/kPa
Q.24 Which of the following statements about a strain gauge is FALSE?
Its resistance changes with applied strain.
It can be used to measure both tension and compression.
It requires an external power source to generate a signal.
It is insensitive to temperature changes.
Explanation - Strain gauges are temperature‑sensitive; temperature compensation (e.g., dummy gauges) is needed for accurate measurement.
Correct answer is: It is insensitive to temperature changes.
Q.25 Which type of sensor typically requires a reference voltage for operation?
Thermocouple
Photovoltaic cell
Resistive temperature detector (RTD)
Hall‑effect sensor
Explanation - Hall sensors output a small voltage proportional to magnetic flux; they need a bias (reference) current and often a supply voltage.
Correct answer is: Hall‑effect sensor
Q.26 The term 'offset error' in a sensor refers to:
A constant difference between the actual output and the ideal output when the input is zero
A proportional error that varies with input magnitude
A random noise component
The error due to temperature drift
Explanation - Offset error shifts the entire transfer function up or down, independent of the input value.
Correct answer is: A constant difference between the actual output and the ideal output when the input is zero
Q.27 Which of the following is an example of a non‑contact temperature sensor?
Thermistor
Thermocouple
Infrared pyrometer
RTD
Explanation - Infrared pyrometers detect thermal radiation emitted by an object, allowing temperature measurement without physical contact.
Correct answer is: Infrared pyrometer
Q.28 In a capacitive proximity sensor, the presence of a target object causes:
An increase in capacitance
A decrease in inductance
A generation of magnetic flux
A change in resistance
Explanation - When a conductive or dielectric object approaches the sensor plates, the effective dielectric constant increases, raising capacitance.
Correct answer is: An increase in capacitance
Q.29 Which sensor would you select to measure the moisture content of soil?
Thermistor
Capacitive moisture sensor
Hall‑effect sensor
Piezoelectric sensor
Explanation - Capacitive sensors detect changes in dielectric constant of soil, which varies with water content.
Correct answer is: Capacitive moisture sensor
Q.30 The term 'dynamic range' of a sensor is defined as:
The ratio between maximum and minimum detectable input signals
The speed at which the sensor can respond
The temperature range over which the sensor operates
The power consumption range
Explanation - Dynamic range = (Maximum measurable signal) / (Minimum detectable signal), often expressed in dB.
Correct answer is: The ratio between maximum and minimum detectable input signals
Q.31 Which of the following sensors is based on the change of optical properties with displacement?
LVDT
Photoelectric encoder
Piezoelectric sensor
Thermocouple
Explanation - Photoelectric encoders use a light source and detector; a moving mask creates pulses corresponding to displacement.
Correct answer is: Photoelectric encoder
Q.32 A sensor with a time constant of 10 ms will:
Fully respond to a step change in 10 ms
Reach about 63% of its final value in 10 ms after a step input
Have a bandwidth of 100 Hz
Never reach steady state
Explanation - Time constant τ is the time required for a first‑order system to reach 1‑e⁻¹ ≈ 63% of its final value.
Correct answer is: Reach about 63% of its final value in 10 ms after a step input
Q.33 Which sensor would be most appropriate for detecting the speed of a rotating shaft in an industrial motor?
Linear Variable Differential Transformer (LVDT)
Rotary Encoder
Thermistor
Capacitive displacement sensor
Explanation - Rotary encoders convert angular position into digital pulses, from which speed can be derived.
Correct answer is: Rotary Encoder
Q.34 An accelerometer based on a MEMS cantilever measures acceleration by:
Detecting changes in resistance due to strain
Measuring charge generated by piezoelectric material
Sensing change in capacitance between movable and fixed plates
Observing variation in magnetic flux
Explanation - MEMS accelerometers often use differential capacitive plates; acceleration moves the proof mass, altering capacitance.
Correct answer is: Sensing change in capacitance between movable and fixed plates
Q.35 For a sensor with a non‑linear characteristic, the most common method to linearize its output is:
Increasing the supply voltage
Applying a digital lookup table or algorithm
Reducing the sensor temperature
Using a larger Wheatstone bridge
Explanation - Software linearization using calibration data stored in a lookup table compensates for non‑linear behavior.
Correct answer is: Applying a digital lookup table or algorithm
Q.36 Which sensor type is most suitable for measuring very low light levels (e.g., starlight)?
Photodiode in photovoltaic mode
Phototransistor
Silicon photomultiplier (SiPM)
LED
Explanation - SiPMs have high gain and can detect single photons, making them ideal for extremely low light conditions.
Correct answer is: Silicon photomultiplier (SiPM)
Q.37 A pressure sensor that outputs a current of 4–20 mA is known as:
Voltage‑output sensor
Current‑loop sensor
Resistance sensor
Capacitive sensor
Explanation - The 4‑20 mA current loop is a standard for industrial process instrumentation, providing noise‑immune transmission.
Correct answer is: Current‑loop sensor
Q.38 The term 'hysteresis' in a sensor characteristic curve is measured as:
Maximum difference between increasing and decreasing output for the same input
Delay time before the sensor responds
Percentage of output drift over time
Ratio of output noise to signal
Explanation - Hysteresis quantifies the loop width between the upward and downward traces of the transfer function.
Correct answer is: Maximum difference between increasing and decreasing output for the same input
Q.39 Which of the following sensors directly converts light into electrical current without requiring an external bias?
Photodiode (photovoltaic mode)
Photodiode (photoconductive mode)
Phototransistor
LED
Explanation - In photovoltaic mode, the photodiode acts like a solar cell, generating current from incident photons without bias.
Correct answer is: Photodiode (photovoltaic mode)
Q.40 If a temperature sensor has a tolerance of ±0.5°C and the measured value is 25°C, what is the possible range of the true temperature?
24.5°C – 25.5°C
24°C – 26°C
23.5°C – 26.5°C
25°C – 30°C
Explanation - Tolerance indicates the measurement can be off by ±0.5°C.
Correct answer is: 24.5°C – 25.5°C
Q.41 In a magnetic proximity sensor, the presence of a ferromagnetic object is detected by:
Changes in inductance
Changes in capacitance
Generation of a voltage
Variation in resistance
Explanation - Ferromagnetic objects alter the magnetic field and thus the inductance of the sensor coil.
Correct answer is: Changes in inductance
Q.42 What is the main advantage of using a digital sensor over an analog sensor in noisy industrial environments?
Higher sensitivity
Lower power consumption
Immunity to noise during transmission
Faster response time
Explanation - Digital signals are less susceptible to electromagnetic interference because they consist of discrete levels.
Correct answer is: Immunity to noise during transmission
Q.43 A sensor whose output voltage decreases as the measured temperature increases is said to have:
Positive temperature coefficient (PTC)
Negative temperature coefficient (NTC)
Zero temperature coefficient
Linear temperature coefficient
Explanation - NTC devices (e.g., NTC thermistors) exhibit decreasing resistance (or voltage across a series resistor) with rising temperature.
Correct answer is: Negative temperature coefficient (NTC)
Q.44 In a pressure transducer that uses a diaphragm and strain gauges, the output is primarily:
Current proportional to pressure
Voltage proportional to pressure
Frequency proportional to pressure
Resistance proportional to pressure
Explanation - Strain gauges form a Wheatstone bridge; pressure‑induced strain changes bridge voltage.
Correct answer is: Voltage proportional to pressure
Q.45 Which sensor is best suited for detecting the level of a liquid in a non‑conductive container?
Capacitive level sensor
Resistive level sensor
Inductive level sensor
Hall‑effect sensor
Explanation - Capacitive sensors detect changes in capacitance caused by the dielectric constant of the liquid, regardless of conductivity.
Correct answer is: Capacitive level sensor
Q.46 The term 'dead band' in a sensor refers to:
A range of input where the output does not change
The maximum measurable input
The sensor’s power consumption at idle
The frequency range over which the sensor operates
Explanation - Dead band is the region around zero where small variations are ignored, often used to avoid chatter.
Correct answer is: A range of input where the output does not change
Q.47 A piezoresistive pressure sensor works on the principle of:
Change in resistance due to applied pressure
Generation of voltage from pressure
Change in capacitance with pressure
Variation of inductance with pressure
Explanation - Piezoresistive materials change resistance when mechanical stress is applied, allowing pressure measurement via a bridge circuit.
Correct answer is: Change in resistance due to applied pressure
Q.48 Which of the following is NOT a typical method of signal conditioning for sensor outputs?
Amplification
Filtering
Quantization
Magnetization
Explanation - Signal conditioning involves amplification, filtering, and conversion (e.g., ADC). Magnetization is not a conditioning technique.
Correct answer is: Magnetization
Q.49 A temperature sensor that measures infrared radiation emitted by an object is called:
Thermistor
RTD
Thermocouple
Infrared pyrometer
Explanation - Infrared pyrometers sense emitted IR energy to infer temperature without contact.
Correct answer is: Infrared pyrometer
Q.50 If a sensor has a gain of 2 V/V and is supplied with 5 V, what will be the output for an input of 0.5 V?
1 V
2 V
5 V
10 V
Explanation - Output = Gain × Input = 2 × 0.5 V = 1 V.
Correct answer is: 1 V
Q.51 Which type of sensor typically requires a reference electrode to operate correctly?
pH sensor
Hall‑effect sensor
Thermocouple
LVDT
Explanation - A pH probe uses a glass electrode and a reference electrode to measure the hydrogen ion activity.
Correct answer is: pH sensor
Q.52 The term 'resolution' of a sensor indicates:
The smallest change in input that can be distinguished
The largest measurable input
The speed of response
The power consumption
Explanation - Resolution is the minimum detectable increment of the measurand, often limited by ADC bits or sensor noise.
Correct answer is: The smallest change in input that can be distinguished
Q.53 A capacitive touch sensor works by detecting:
Changes in magnetic field
Changes in capacitance caused by a finger
Generation of acoustic waves
Variation in resistance
Explanation - When a finger approaches, the human body adds capacitance, which the sensor detects.
Correct answer is: Changes in capacitance caused by a finger
Q.54 A sensor with a linear output of 2 mV/°C is used to measure temperature from 0°C to 100°C. What is the full‑scale output?
0.2 V
0.5 V
2 V
5 V
Explanation - Full‑scale = 2 mV/°C × 100°C = 200 mV = 0.2 V.
Correct answer is: 0.2 V
Q.55 Which of the following sensors can be used for detecting gas concentration?
Electrochemical gas sensor
Piezoelectric sensor
Thermocouple
Linear Variable Differential Transformer
Explanation - Electrochemical sensors generate a current proportional to gas concentration due to redox reactions.
Correct answer is: Electrochemical gas sensor
Q.56 A sensor that outputs a frequency proportional to the measured variable is known as:
Frequency‑output sensor
Voltage‑output sensor
Current‑output sensor
Resistance‑output sensor
Explanation - Frequency‑output sensors (e.g., some flow meters) encode the measurement as a pulse frequency.
Correct answer is: Frequency‑output sensor
Q.57 The primary reason to use a shielded cable for sensor signal transmission is:
To reduce power consumption
To protect against electromagnetic interference (EMI)
To increase the sensor’s sensitivity
To improve thermal conductivity
Explanation - Shielding provides a conductive barrier that absorbs external EMI, preserving signal integrity.
Correct answer is: To protect against electromagnetic interference (EMI)
Q.58 Which sensor type is most appropriate for measuring angular displacement in a high‑precision CNC machine?
Linear Variable Differential Transformer (LVDT)
Rotary Encoder with high resolution
Capacitive proximity sensor
Thermocouple
Explanation - High‑resolution rotary encoders provide precise angular position data essential for CNC control.
Correct answer is: Rotary Encoder with high resolution
Q.59 A pressure sensor that utilizes a piezoresistive silicon diaphragm typically has which characteristic?
Very high temperature range (>500°C)
Excellent linearity over a wide range
Low sensitivity to temperature
High output voltage without amplification
Explanation - Piezoresistive silicon diaphragms exhibit near‑linear output over their designed pressure range.
Correct answer is: Excellent linearity over a wide range
Q.60 For a sensor that requires a 5 V supply and draws 2 mA, what is its power consumption?
10 mW
2.5 mW
0.1 W
5 W
Explanation - Power = V × I = 5 V × 2 mA = 10 mW.
Correct answer is: 10 mW
Q.61 The output of a photodiode operated in reverse‑bias mode is primarily:
Current proportional to light intensity
Voltage proportional to light intensity
Resistance proportional to light intensity
Frequency proportional to light intensity
Explanation - In photoconductive mode (reverse bias), the photocurrent is linearly related to illumination.
Correct answer is: Current proportional to light intensity
Q.62 Which sensor would you select to monitor the level of a corrosive liquid inside a sealed metal tank?
Ultrasonic level sensor
Resistive level sensor
Capacitive level sensor
Inductive level sensor
Explanation - Ultrasonic sensors are non‑contact and can operate through metal walls (if a suitable window is provided), making them ideal for sealed tanks.
Correct answer is: Ultrasonic level sensor
Q.63 A sensor that has a response time of 5 ms is said to have a:
Bandwidth of 200 Hz
Bandwidth of 5 Hz
Bandwidth of 70 Hz
Bandwidth of 100 Hz
Explanation - Approximate bandwidth ≈ 0.35 / rise time = 0.35 / 0.005 s ≈ 70 Hz. (Using 0.35 constant gives ~70 Hz, but many textbooks use 1/(2π·τ) ≈ 31.8 Hz. To keep answer consistent, we consider typical rule of thumb: bandwidth ≈ 0.35 / rise time → 70 Hz.
Correct answer is: Bandwidth of 70 Hz
Q.64 Which of the following best describes a ‘smart sensor’?
A sensor with built‑in signal conditioning and digital communication capability
A sensor that only works at high temperatures
A sensor made of smart materials like shape‑memory alloy
A sensor that requires manual calibration every hour
Explanation - Smart sensors integrate conditioning, processing, and communication (e.g., I²C, SPI) in one package.
Correct answer is: A sensor with built‑in signal conditioning and digital communication capability
Q.65 In a differential pressure sensor, if the measured pressure difference is zero, the output voltage will be:
Maximum
Zero (or a defined offset)
Negative maximum
Indeterminate
Explanation - At zero differential pressure, the bridge is balanced, giving zero differential voltage (or a programmed offset).
Correct answer is: Zero (or a defined offset)
Q.66 A sensor that outputs a digital code directly proportional to the measured quantity is called:
Analog sensor
Digital sensor
Hybrid sensor
Passive sensor
Explanation - Digital sensors incorporate ADCs and provide a digital representation of the measurand.
Correct answer is: Digital sensor
Q.67 What is the main disadvantage of using a thermocouple for precise temperature measurement in a laboratory?
Low temperature range
Non‑linear output and need for cold‑junction compensation
High power consumption
Slow response time
Explanation - Thermocouples generate small voltages that are non‑linear and require compensation for the reference junction temperature.
Correct answer is: Non‑linear output and need for cold‑junction compensation
Q.68 A sensor’s ‘bandwidth’ is most closely related to:
Maximum input amplitude
Maximum frequency at which the sensor can accurately respond
Maximum temperature range
Maximum power consumption
Explanation - Bandwidth defines the highest frequency component the sensor can follow without significant attenuation.
Correct answer is: Maximum frequency at which the sensor can accurately respond
Q.69 Which material is commonly used for the sensing element in a piezoelectric accelerometer?
Quartz
Silicon
Aluminum
Copper
Explanation - Quartz exhibits strong piezoelectric properties and is widely used in accelerometers.
Correct answer is: Quartz
Q.70 In a resistive temperature detector (RTD), the temperature coefficient of resistance (α) is typically:
Positive
Negative
Zero
Variable with temperature
Explanation - RTDs (e.g., Pt100) increase resistance as temperature rises, giving a positive α.
Correct answer is: Positive
Q.71 Which sensor type is most appropriate for detecting the presence of a non‑metallic object (e.g., plastic) on a conveyor belt?
Inductive proximity sensor
Capacitive proximity sensor
Magnetic proximity sensor
Hall‑effect sensor
Explanation - Capacitive sensors can detect changes in dielectric constant caused by non‑conductive objects.
Correct answer is: Capacitive proximity sensor
Q.72 A sensor that exhibits a ‘gain error’ will:
Have an output that is scaled incorrectly relative to the input
Show a constant offset irrespective of input
Respond slower than specified
Produce random noise
Explanation - Gain error changes the slope of the transfer function, causing proportional scaling errors.
Correct answer is: Have an output that is scaled incorrectly relative to the input
Q.73 The term ‘cold‑junction compensation’ is associated with which sensor?
RTD
Thermocouple
Photodiode
Hall‑effect sensor
Explanation - Because the thermocouple voltage is measured relative to a reference junction, its temperature must be compensated.
Correct answer is: Thermocouple
Q.74 A sensor that converts a physical quantity directly into a frequency signal typically uses:
A crystal oscillator whose frequency varies with the measurand
A Wheatstone bridge
A photodiode array
A thermoelectric module
Explanation - Frequency‑output sensors often employ oscillators where the resonant frequency shifts with the sensed parameter.
Correct answer is: A crystal oscillator whose frequency varies with the measurand
Q.75 For a sensor with a linearity error of ±0.2% of full scale, what is the maximum possible deviation at a full‑scale input of 100 units?
±0.2 units
±0.02 units
±2 units
±20 units
Explanation - Linearity error = 0.2% of 100 = 0.2 units.
Correct answer is: ±0.2 units
Q.76 Which sensor technology is most commonly used for measuring the concentration of CO₂ in indoor air quality monitors?
NDIR (Non‑Dispersive Infrared) sensor
Electrochemical sensor
Piezoresistive sensor
Thermocouple
Explanation - NDIR sensors detect CO₂ by measuring absorption of infrared light at a specific wavelength.
Correct answer is: NDIR (Non‑Dispersive Infrared) sensor
Q.77 A sensor that measures the tilt angle by detecting the shift in liquid level inside a sealed tube is called:
Inclinometer
Accelerometer
Gyroscope
Barometer
Explanation - Liquid‑filled inclinometers use the movement of liquid to sense tilt angle.
Correct answer is: Inclinometer
Q.78 Which of the following is a primary advantage of using a fiber‑optic sensor for displacement measurement?
Immunity to electromagnetic interference
Low cost
Very high power consumption
Simple wiring
Explanation - Fiber‑optic sensors transmit light, making them resistant to EMI, ideal for harsh industrial environments.
Correct answer is: Immunity to electromagnetic interference
Q.79 The term ‘hysteresis’ in a temperature sensor is most critical for which application?
Fast temperature cycling where repeatability matters
Static temperature monitoring with long dwell times
Measuring very low temperatures
Measuring pressure
Explanation - Hysteresis causes different readings for rising vs. falling temperature, affecting dynamic measurements.
Correct answer is: Fast temperature cycling where repeatability matters
Q.80 A pressure transducer that uses a silicon diaphragm with four strain gauges arranged in a Wheatstone bridge is called:
Piezoresistive pressure sensor
Capacitive pressure sensor
Inductive pressure sensor
Thermocouple pressure sensor
Explanation - The silicon diaphragm with strain gauges forms a piezoresistive pressure sensor.
Correct answer is: Piezoresistive pressure sensor
Q.81 Which sensor type would you use to detect the presence of a magnetic field in a brushless DC motor?
Hall‑effect sensor
Inductive proximity sensor
Capacitive sensor
Thermocouple
Explanation - Hall‑effect sensors are commonly used for rotor position sensing in BLDC motors.
Correct answer is: Hall‑effect sensor
Q.82 The output of a sensor that provides a 4‑20 mA current loop will be:
A voltage proportional to the measured variable
A current proportional to the measured variable
A resistance proportional to the measured variable
A frequency proportional to the measured variable
Explanation - The 4‑20 mA loop encodes the measurement as a current signal.
Correct answer is: A current proportional to the measured variable
Q.83 In a temperature sensor, the term ‘self‑heating’ refers to:
The sensor’s own temperature rise due to its excitation current
The sensor’s ability to heat the measured object
The sensor’s resistance decreasing with temperature
The sensor’s need for external heating
Explanation - Self‑heating causes measurement error, especially in low‑power sensors like RTDs when high currents are used.
Correct answer is: The sensor’s own temperature rise due to its excitation current
Q.84 Which sensor technology relies on the change of refractive index to detect pressure changes?
Fiber‑optic pressure sensor
Piezoelectric sensor
Thermocouple
Hall‑effect sensor
Explanation - Fiber‑optic pressure sensors detect pressure‑induced changes in the refractive index of the sensing element.
Correct answer is: Fiber‑optic pressure sensor
Q.85 A sensor with a high ‘signal‑to‑noise ratio’ (SNR) indicates:
The sensor’s output is dominated by noise
The sensor’s output signal is much larger than the noise floor
The sensor has a wide bandwidth
The sensor consumes high power
Explanation - High SNR means the useful signal stands out clearly above noise, leading to accurate measurements.
Correct answer is: The sensor’s output signal is much larger than the noise floor
Q.86 Which of the following sensors would be most appropriate for measuring the speed of a flowing gas in a pipe?
Thermocouple
Ultrasonic flow sensor
Capacitive level sensor
LVDT
Explanation - Ultrasonic flow meters measure gas velocity by timing the transit of sound waves.
Correct answer is: Ultrasonic flow sensor
Q.87 A sensor that uses a thin film of metal whose resistance changes with strain is known as:
Strain gauge
Thermistor
Photodiode
Hall‑effect sensor
Explanation - Strain gauges convert mechanical deformation into a resistance change.
Correct answer is: Strain gauge
Q.88 What is the main purpose of a ‘dummy gauge’ in a Wheatstone bridge arrangement for strain measurement?
To double the sensitivity
To compensate for temperature effects
To increase the output voltage
To provide a reference voltage
Explanation - A dummy gauge experiences the same temperature as the active gauge but no strain, cancelling temperature‑induced resistance changes.
Correct answer is: To compensate for temperature effects
Q.89 The primary operating principle of a capacitive humidity sensor is:
Change in capacitance due to water vapor adsorption
Generation of voltage from humidity
Change in resistance due to humidity
Emission of infrared radiation
Explanation - Water molecules alter the dielectric constant between the sensor’s plates, changing capacitance.
Correct answer is: Change in capacitance due to water vapor adsorption
Q.90 In a digital temperature sensor using an ADC with 12‑bit resolution over a 0‑100°C range, what is the smallest temperature increment it can resolve?
0.024°C
0.1°C
0.5°C
1°C
Explanation - Resolution = range / (2^bits – 1) = 100 / 4095 ≈ 0.0244°C.
Correct answer is: 0.024°C
Q.91 Which of the following sensor types is inherently immune to corrosion when immersed in aggressive chemicals?
Optical fiber sensor with proper coating
Inductive proximity sensor
Thermocouple with exposed junction
Strain gauge with metallic foil
Explanation - Fiber‑optic sensors can be hermetically sealed and coated to resist corrosion, unlike exposed metal sensors.
Correct answer is: Optical fiber sensor with proper coating
Q.92 A sensor that detects the presence of an object by measuring the change in reflected infrared light is called:
Photoelectric sensor (reflective type)
Inductive proximity sensor
Capacitive proximity sensor
Hall‑effect sensor
Explanation - Reflective photoelectric sensors emit IR light and detect its reflection from an object.
Correct answer is: Photoelectric sensor (reflective type)
Q.93 The term ‘offset drift’ in a sensor is caused primarily by:
Temperature changes over time
Mechanical vibration
Supply voltage fluctuations
Aging of electronic components
Explanation - Offset drift often results from temperature‑dependent shifts in the sensor’s baseline output.
Correct answer is: Temperature changes over time
Q.94 A sensor that measures the angle of rotation by generating two square‑wave signals 90° out of phase is known as:
Quadrature encoder
Absolute encoder
Linear encoder
Potentiometer
Explanation - Quadrature encoders provide two phase‑shifted signals for direction and resolution detection.
Correct answer is: Quadrature encoder
Q.95 Which of the following is a common method to increase the sensitivity of a resistive sensor?
Increasing the supply voltage
Using a Wheatstone bridge configuration
Reducing the sensor’s temperature coefficient
Adding a low‑pass filter
Explanation - A bridge amplifies small resistance changes into measurable voltage differences, enhancing sensitivity.
Correct answer is: Using a Wheatstone bridge configuration
Q.96 In a piezoelectric sensor, the generated charge is proportional to:
Static pressure
Rate of change of mechanical stress
Temperature
Magnetic field
Explanation - Piezoelectric effect produces charge when the stress varies; static pressure yields little output.
Correct answer is: Rate of change of mechanical stress
Q.97 Which sensor type is most suitable for measuring very high frequencies (above 1 MHz) in acoustic applications?
Piezoelectric microphone
Capacitive microphone
Dynamic (coil‑voice) microphone
Condensation microphone
Explanation - Piezoelectric microphones have fast response and can handle ultrasonic frequencies.
Correct answer is: Piezoelectric microphone
Q.98 A sensor that uses the change in resistance of a semiconductor material with light exposure is called:
Photoconductor (photoresistor)
Photodiode
Phototransistor
Solar cell
Explanation - Photoconductors exhibit a decrease in resistance when illuminated.
Correct answer is: Photoconductor (photoresistor)
Q.99 When a sensor’s specification lists ‘±0.5% FS non‑linearity’, what does ‘FS’ stand for?
Full Scale
Frequency Shift
Fast Sampling
Force Sensitivity
Explanation - FS refers to the full‑scale range of the sensor; non‑linearity is expressed as a percentage of this range.
Correct answer is: Full Scale
Q.100 A sensor that measures the concentration of oxygen in exhaust gases by measuring the voltage generated from a solid‑state electrolyte is:
Zirconia (λ) sensor
NDIR sensor
Electrochemical oxygen sensor
Catalytic bead sensor
Explanation - Zirconia sensors (lambda sensors) generate a voltage proportional to the oxygen concentration difference across the electrolyte.
Correct answer is: Zirconia (λ) sensor
Q.101 A pressure sensor that uses a diaphragm and measures the change in capacitance between two plates is known as:
Capacitive pressure sensor
Piezoresistive pressure sensor
Inductive pressure sensor
Thermocouple pressure sensor
Explanation - Capacitive pressure sensors detect diaphragm deflection as a change in capacitance.
Correct answer is: Capacitive pressure sensor
Q.102 The main disadvantage of a capacitive proximity sensor when used near conductive liquids is:
Reduced sensitivity due to dielectric constant changes
Corrosion of the sensor plates
Increased power consumption
Magnetic interference
Explanation - Conductive liquids alter the dielectric environment unpredictably, affecting capacitance measurement.
Correct answer is: Reduced sensitivity due to dielectric constant changes
Q.103 In a temperature measurement system, the term ‘span error’ refers to:
A constant offset error across the range
An error that scales with the measurement range
A random noise component
A drift over time
Explanation - Span error is a gain error; it changes the slope of the transfer function, affecting the full‑scale output.
Correct answer is: An error that scales with the measurement range
Q.104 Which type of sensor is commonly used for detecting the position of a rotating shaft in automotive engine timing?
Hall‑effect sensor
Capacitive displacement sensor
Thermocouple
LVDT
Explanation - Hall sensors detect the passing of teeth on a rotating toothed wheel, providing timing signals.
Correct answer is: Hall‑effect sensor
Q.105 A sensor with a ‘single‑ended output’ compared to a ‘differential output’ is more susceptible to:
Common‑mode noise
Temperature variation
Linearity error
Hysteresis
Explanation - Differential outputs reject common‑mode noise, while single‑ended signals pick it up more readily.
Correct answer is: Common‑mode noise
Q.106 Which of the following is a primary reason to calibrate a sensor periodically?
To adjust the sensor’s power consumption
To compensate for drift and aging effects
To increase the sensor’s bandwidth
To change its measurement range
Explanation - Calibration realigns the sensor’s output with known standards, mitigating drift and aging.
Correct answer is: To compensate for drift and aging effects
Q.107 A sensor that detects the presence of a liquid level by measuring the change in dielectric constant of the surrounding medium is:
Capacitive level sensor
Ultrasonic level sensor
Radar level sensor
Float switch
Explanation - Capacitive level sensors sense level by the change in capacitance caused by the liquid’s dielectric constant.
Correct answer is: Capacitive level sensor
Q.108 The output of a photodiode operating in photovoltaic mode is:
A voltage proportional to light intensity
A current proportional to light intensity
A resistance proportional to light intensity
A frequency proportional to light intensity
Explanation - In photovoltaic mode, the photodiode generates a current directly proportional to the incident light.
Correct answer is: A current proportional to light intensity
Q.109 Which sensor element exhibits a negative temperature coefficient (NTC) behavior?
Thermistor (NTC type)
RTD
Thermocouple
Hall‑effect sensor
Explanation - NTC thermistors decrease resistance as temperature rises.
Correct answer is: Thermistor (NTC type)
Q.110 A sensor that outputs a voltage proportional to the concentration of a specific gas using a catalytic reaction is called:
Catalytic bead gas sensor
NDIR sensor
Electrochemical gas sensor
Photoionization detector
Explanation - Catalytic bead sensors oxidize combustible gases, producing a temperature change that is converted to voltage.
Correct answer is: Catalytic bead gas sensor
Q.111 In a sensor datasheet, the term ‘linearity error’ is typically expressed as:
Percentage of full‑scale output
Degrees Celsius
Ohms
Seconds
Explanation - Linearity error is usually given as a percentage of the full‑scale range to indicate deviation from ideal linear behavior.
Correct answer is: Percentage of full‑scale output
Q.112 Which of the following sensor technologies can be used to measure both pressure and temperature simultaneously?
Silicon pressure sensor with integrated temperature compensation
Thermocouple
LVDT
Photodiode
Explanation - Modern silicon pressure sensors often include on‑chip temperature sensing for simultaneous measurement.
Correct answer is: Silicon pressure sensor with integrated temperature compensation
Q.113 A sensor that converts light intensity into a voltage without any external bias is known as:
Photovoltaic sensor
Photoconductive sensor
Phototransistor
LED
Explanation - Photovoltaic sensors (e.g., solar cells) generate voltage directly from incident light.
Correct answer is: Photovoltaic sensor
Q.114 The term ‘dead‑zone’ in a proximity sensor characteristic curve is synonymous with:
Dead band
Hysteresis
Linearity error
Gain error
Explanation - Dead‑zone (or dead band) indicates a region where small changes in input do not affect the output.
Correct answer is: Dead band
Q.115 Which sensor type is most commonly used for detecting the rotational speed of a fan in HVAC systems?
Tachometer (optical or magnetic)
Thermocouple
Capacitive humidity sensor
Strain gauge load cell
Explanation - Tachometers use optical slots or magnetic pickups to generate pulses proportional to rotation speed.
Correct answer is: Tachometer (optical or magnetic)
Q.116 A sensor that measures the flow rate of a liquid by detecting the Doppler shift of an ultrasonic beam is called:
Ultrasonic Doppler flow meter
Thermal flow meter
Coriolis flow meter
Vortex shedding flow meter
Explanation - Doppler ultrasonic meters calculate flow based on frequency shift of reflected ultrasound from particles in the fluid.
Correct answer is: Ultrasonic Doppler flow meter
Q.117 Which of the following sensors is typically employed for detecting the position of a magnetic reed switch?
Hall‑effect sensor
Capacitive sensor
Inductive proximity sensor
Thermistor
Explanation - Hall sensors detect magnetic fields and are often used alongside reed switches for precise position sensing.
Correct answer is: Hall‑effect sensor
Q.118 A sensor whose output is a digital word representing the measured value, obtained after analog‑to‑digital conversion, is called:
Digital sensor
Analog sensor
Passive sensor
Smart sensor
Explanation - Digital sensors embed ADCs and provide processed digital data directly.
Correct answer is: Digital sensor
Q.119 When a sensor’s specification lists ‘±0.1% FS repeatability’, what does this indicate?
The sensor’s output can vary up to 0.1% of full‑scale when the same input is applied repeatedly
The sensor’s offset error is 0.1% FS
The sensor’s linearity error is 0.1% FS
The sensor’s temperature coefficient is 0.1% FS
Explanation - Repeatability refers to the consistency of the sensor’s output under identical conditions.
Correct answer is: The sensor’s output can vary up to 0.1% of full‑scale when the same input is applied repeatedly
Q.120 Which sensor technology is best suited for measuring very small displacements (nanometer range) in precision metrology?
Interferometric optical sensor
LVDT
Capacitive sensor
Potentiometer
Explanation - Interferometry can resolve displacements on the order of a wavelength of light (~nanometers).
Correct answer is: Interferometric optical sensor
Q.121 A sensor that measures the concentration of a gas by measuring the change in resistance of a metal‑oxide layer is known as:
Metal‑oxide semiconductor (MOS) gas sensor
NDIR sensor
Electrochemical sensor
Catalytic bead sensor
Explanation - MOS gas sensors change resistance when gas molecules interact with the oxide surface.
Correct answer is: Metal‑oxide semiconductor (MOS) gas sensor
Q.122 In a sensor system, the purpose of an anti‑aliasing filter is to:
Prevent high‑frequency components from folding into the sampled bandwidth
Increase sensor sensitivity
Reduce power consumption
Compensate for temperature drift
Explanation - Anti‑aliasing filters limit the input bandwidth to below half the sampling rate, avoiding aliasing.
Correct answer is: Prevent high‑frequency components from folding into the sampled bandwidth
Q.123 A sensor that measures the tilt of a platform by detecting the change in resistance of a fluid‑filled bubble level is called:
Inclinometer (fluid type)
Gyroscope
Accelerometer
Magnetometer
Explanation - Fluid‑filled inclinometers use the shift of a conductive fluid bubble to change resistance.
Correct answer is: Inclinometer (fluid type)
Q.124 Which sensor type is typically used for measuring the speed of a rotating shaft in high‑precision CNC machines, offering sub‑arc‑second resolution?
Optical incremental encoder
Magnetic Hall sensor
Capacitive proximity sensor
Inductive proximity sensor
Explanation - Optical encoders provide very fine resolution through precise light/slot patterns.
Correct answer is: Optical incremental encoder
Q.125 A sensor that utilizes the change in refractive index of a fiber core due to pressure is called:
Fiber‑optic pressure sensor
Piezoelectric pressure sensor
Capacitive pressure sensor
Thermocouple pressure sensor
Explanation - Pressure changes alter the fiber’s refractive index, which can be measured via interferometry.
Correct answer is: Fiber‑optic pressure sensor
Q.126 In a sensor’s transfer function, a ‘gain error’ will affect which part of the output?
The slope of the output vs. input line
The intercept (offset) at zero input
The noise floor
The maximum bandwidth
Explanation - Gain error changes the proportionality factor (slope) between input and output.
Correct answer is: The slope of the output vs. input line
Q.127 Which of the following sensors typically requires a reference electrode for proper operation?
pH electrode
Hall‑effect sensor
Thermocouple
LVDT
Explanation - A pH probe uses a glass electrode and a reference electrode to measure hydrogen ion activity.
Correct answer is: pH electrode
Q.128 A sensor that measures the presence of a magnetic field by producing a voltage proportional to the field strength is known as:
Hall‑effect sensor
Inductive sensor
Capacitive sensor
Thermistor
Explanation - Hall sensors directly convert magnetic flux density into a voltage.
Correct answer is: Hall‑effect sensor
Q.129 When a sensor’s output is digitized by a 10‑bit ADC over a 0‑5 V range, what is the voltage resolution?
4.88 mV
5 V
0.5 V
10 V
Explanation - Resolution = 5 V / (2¹⁰‑1) ≈ 4.88 mV.
Correct answer is: 4.88 mV
Q.130 A sensor that uses a piezoelectric crystal to generate voltage when struck by a sound wave is called:
Piezoelectric microphone
Capacitive microphone
Dynamic microphone
Condensation microphone
Explanation - Piezo microphones convert acoustic pressure into charge via the piezoelectric effect.
Correct answer is: Piezoelectric microphone
Q.131 The primary advantage of using a differential pressure sensor for level measurement in a closed tank is:
It eliminates the need for a reference pressure
It provides direct temperature measurement
It reduces sensor size
It eliminates the need for a vented connection
Explanation - Differential sensors measure pressure difference between tank and a reference point, allowing accurate level measurement without external venting.
Correct answer is: It eliminates the need for a reference pressure
Q.132 A sensor that measures the change in resistance of a metallic strip due to temperature is called:
RTD (Resistance Temperature Detector)
Thermocouple
Thermistor
Photodiode
Explanation - RTDs, typically made from platinum, exhibit predictable resistance change with temperature.
Correct answer is: RTD (Resistance Temperature Detector)
Q.133 Which sensor type is most suitable for detecting the level of a highly conductive liquid (e.g., water) in a tank?
Capacitive level sensor
Inductive proximity sensor
Ultrasonic level sensor
Magnetic float sensor
Explanation - Capacitive sensors can detect conductive liquids via changes in dielectric constant.
Correct answer is: Capacitive level sensor
Q.134 A sensor that detects motion by measuring changes in the magnetic field of a rotating magnet is called:
Hall‑effect sensor
Inductive proximity sensor
Capacitive proximity sensor
LVDT
Explanation - Hall sensors detect variations in magnetic flux as a magnet rotates.
Correct answer is: Hall‑effect sensor
Q.135 When a sensor exhibits a ‘temperature coefficient of sensitivity’ (TCS), it means:
Its sensitivity changes with temperature
Its offset changes with temperature
Its bandwidth changes with temperature
Its power consumption changes with temperature
Explanation - TCS quantifies how the sensor’s gain varies as temperature varies.
Correct answer is: Its sensitivity changes with temperature
Q.136 Which of the following is NOT a common method for reducing noise in sensor signal conditioning?
Low‑pass filtering
Shielded cabling
Increasing sensor supply voltage
Differential amplification
Explanation - Raising supply voltage does not inherently reduce noise and can increase power consumption.
Correct answer is: Increasing sensor supply voltage
Q.137 A sensor that measures the concentration of carbon monoxide using an electrochemical cell works by:
Oxidizing CO at an electrode and measuring the resulting current
Measuring infrared absorption of CO
Detecting the magnetic field generated by CO
Measuring the change in resistance of a metal oxide
Explanation - Electrochemical CO sensors generate a current proportional to the amount of CO oxidized at the sensing electrode.
Correct answer is: Oxidizing CO at an electrode and measuring the resulting current
Q.138 In a sensor system, the term ‘bandwidth limitation’ is often introduced by:
The sensor’s mechanical resonance
The ADC sampling rate
The power supply voltage
The sensor’s color
Explanation - Sampling rate imposes a Nyquist limit, restricting the highest frequency that can be accurately captured.
Correct answer is: The ADC sampling rate
Q.139 A sensor that utilizes a piezoelectric crystal to generate voltage when subjected to pressure is called:
Piezoelectric pressure sensor
Capacitive pressure sensor
Strain gauge pressure sensor
Thermocouple pressure sensor
Explanation - Piezoelectric pressure sensors directly convert dynamic pressure into voltage via the piezoelectric effect.
Correct answer is: Piezoelectric pressure sensor
Q.140 Which sensor characteristic is most directly affected by the supply voltage stability?
Offset error
Linearity error
Hysteresis
Resolution
Explanation - Supply voltage variations can shift the baseline (offset) of many sensor outputs.
Correct answer is: Offset error
Q.141 A sensor that measures the presence of a liquid level by detecting the change in resonant frequency of an acoustic cavity is called:
Acoustic (ultrasonic) level sensor
Capacitive level sensor
Radar level sensor
Float switch
Explanation - Acoustic sensors use the time‑of‑flight or resonant frequency of sound waves to infer level.
Correct answer is: Acoustic (ultrasonic) level sensor
Q.142 When calibrating a sensor, a ‘two‑point calibration’ involves:
Measuring at two known reference points to define slope and offset
Measuring temperature at two different times
Using two sensors simultaneously
Applying two different power supplies
Explanation - Two‑point calibration establishes gain (slope) and offset by aligning the sensor’s output at two known inputs.
Correct answer is: Measuring at two known reference points to define slope and offset
Q.143 Which sensor type is best suited for measuring very low pressures (micro‑Pascal range) in vacuum applications?
Capacitive MEMS pressure sensor
Piezoelectric pressure sensor
Strain gauge pressure sensor
Thermocouple
Explanation - Capacitive MEMS sensors can achieve high sensitivity and low pressure ranges suitable for vacuum.
Correct answer is: Capacitive MEMS pressure sensor
Q.144 A sensor that detects the presence of a metal object by measuring changes in inductance is known as:
Inductive proximity sensor
Capacitive proximity sensor
Photoelectric sensor
Hall‑effect sensor
Explanation - Inductive sensors sense metallic objects via changes in coil inductance caused by eddy currents.
Correct answer is: Inductive proximity sensor
Q.145 The term ‘dynamic range’ of a sensor is expressed as:
Ratio of the largest to smallest detectable signal
Difference between maximum and minimum input voltage
Maximum sampling frequency
Power consumption range
Explanation - Dynamic range = (Maximum signal) / (Minimum detectable signal), often in dB.
Correct answer is: Ratio of the largest to smallest detectable signal
Q.146 Which sensor is commonly used for detecting the angular position of a shaft in a brushless DC motor by providing a sinusoidal voltage output?
Hall‑effect sensor
Resolver
Potentiometer
Photodiode
Explanation - Resolvers output sinusoidal voltages whose phase corresponds to shaft angle, used in high‑reliability motor control.
Correct answer is: Resolver
Q.147 A sensor that measures the amount of light by varying its resistance is called:
Photoresistor (LDR)
Photodiode
Phototransistor
Solar cell
Explanation - LDRs (Light Dependent Resistors) change resistance with illumination intensity.
Correct answer is: Photoresistor (LDR)
Q.148 When a sensor’s specification mentions ‘cold‑junction compensation’, it is most likely a:
Thermocouple
RTD
Thermistor
Hall‑effect sensor
Explanation - Thermocouples require compensation for the reference (cold) junction temperature to obtain accurate readings.
Correct answer is: Thermocouple
Q.149 In a sensor data sheet, the term ‘settling time’ refers to:
The time required for the sensor output to reach and stay within a specified error band after a step change
The time the sensor takes to power up
The time between calibration cycles
The time the sensor can operate before overheating
Explanation - Settling time characterizes how quickly a sensor stabilizes after an abrupt input change.
Correct answer is: The time required for the sensor output to reach and stay within a specified error band after a step change
Q.150 A sensor that detects the presence of an object by emitting and receiving a magnetic field is called:
Inductive proximity sensor
Capacitive proximity sensor
Photoelectric sensor
Ultrasonic sensor
Explanation - Inductive sensors generate a magnetic field and sense changes caused by nearby conductive objects.
Correct answer is: Inductive proximity sensor
Q.151 Which sensor characteristic is most directly influenced by the material’s temperature coefficient of resistance (TCR)?
Sensitivity
Linearity
Hysteresis
Response time
Explanation - TCR defines how resistance (and thus output) changes with temperature, affecting the sensor’s sensitivity to the measurand.
Correct answer is: Sensitivity
Q.152 A sensor that measures the concentration of a specific gas by measuring the change in infrared absorption at a characteristic wavelength is called:
NDIR sensor
Electrochemical sensor
Catalytic bead sensor
MOS gas sensor
Explanation - Non‑Dispersive Infrared (NDIR) sensors detect gases based on specific IR absorption lines.
Correct answer is: NDIR sensor
Q.153 Which of the following sensors provides a direct measurement of angular displacement without any mechanical contact?
Optical rotary encoder
Potentiometer
Hall‑effect sensor
LVDT
Explanation - Optical encoders read light through a patterned disk, providing non‑contact angular position data.
Correct answer is: Optical rotary encoder