Sensors and Signal Conditioning - Sensors and Bioinstrumentation - Biomedical Engineering Previous Year Questions

1

2020 · Biomedical Engineering · Sensors and Bioinstrumentation · Sensors and Signal Conditioning

Biomedical Engineering (BM) 2020

Two dyes X and Y having concentrations in the ratio 0.25 in identical cuvettes were subjected to absorption measurements in a spectrophotometer. The estimated ratio of their absorbance is 0.5. The ratio of their molar extinction coefficients is ________.

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2

2020 · Biomedical Engineering · Sensors and Bioinstrumentation · Sensors and Signal Conditioning

Biomedical Engineering (BM) 2020

An 830 nm laser Doppler flow meter probe is oriented at an angle of 60° to the flow axis. If the average flow velocity is 3 cm/s, the magnitude of Doppler shift frequency (kHz) is ________ (rounded off to one decimal place).

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3

2020 · Biomedical Engineering · Sensors and Bioinstrumentation · Sensors and Signal Conditioning

Biomedical Engineering (BM) 2020

The arrangement of four resistors of equal value in the diaphragm of a physiological pressure measurement catheter is shown below. The applied pressure is observed to cause an increase in length of resistors R2, R4 and an increase in cross sectional area in R1 and R3. The operation results in an equal change in the values of all four resistors. Which among the configuration given below should be used to connect the resistors to form a Wheatstone bridge so that bridge output voltage is proportional to the change in resistance of individual resistors?

A

I only

B

II only

C

Neither I nor II

D

Both I and II

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4

2021 · Biomedical Engineering · Sensors and Bioinstrumentation · Sensors and Signal Conditioning

Biomedical Engineering (BM) 2021

Which of the following displacement sensors is known to have a high sensitivity and a relatively larger measurement range?

A

Strain gauge

B

Capacitive sensor

C

LVDT

D

Piezoelectric sensor

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5

2021 · Biomedical Engineering · Sensors and Bioinstrumentation · Sensors and Signal Conditioning

Biomedical Engineering (BM) 2021

Which of the following temperature sensors is used in contact-type digital thermometers for measuring body temperature?

A

Thermocouple

B

Thermistor

C

Resistance temperature detector

D

Infrared LED-photodetector pair

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6

2022 · Biomedical Engineering · Sensors and Bioinstrumentation · Sensors and Signal Conditioning

Biomedical Engineering (BM) 2022

Which of the following statements related to the operating principle of pulse oximetry are CORRECT?

A

Pulse oximeter can non-invasively determine arterial oxygen saturation (SpO₂) by analyzing the light transmitted through the skin during the systolic phase of the blood flow through the tissue

B

In a pulse oximeter, isosbestic wavelength is the wavelength at which Hb and HbO₂ have same optical absorbance

C

Pulse oximeter can accurately determine the SpO₂ of blood by computing the ratio of absorbances at 660 nm and 905 nm wavelengths

D

Pulse oximeter can accurately determine the SpO₂ of blood by computing the ratio of absorbances at 850 nm and 950 nm wavelengths

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7

2022 · Biomedical Engineering · Sensors and Bioinstrumentation · Sensors and Signal Conditioning

Biomedical Engineering (BM) 2022

A Hall effect flow meter is used to measure the volumetric flow through a blood vessel. The flow meter induces a magnetic field across the vessel and uses a voltmeter to measure the voltage across the vessel which is normal to both magnetic field and blood flow. A caliper is used to measure the vessel diameter. The system calculated the flow rate to be 100 cm³.s⁻¹ using the known magnetic field, and measured values of voltage and vessel diameter.
After the measurement, a calibration is performed, and it is discovered that the voltmeter was measuring 40% larger than the actual value and the caliper was measuring the diameter 10% smaller than the actual value.
Assuming a uniform flow profile along the vessel and ignoring viscosity, the actual blood flow is ______ cm³.s⁻¹ (rounded off to two decimal places).

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8

2022 · Biomedical Engineering · Sensors and Bioinstrumentation · Sensors and Signal Conditioning

Biomedical Engineering (BM) 2022

A catheter based arterial blood pressure measurement device uses a flexible diaphragm mounted with four identical strain gauges in a Wheatstone bridge configuration as shown in the figure. Assume that the strain gauges have a nominal resistance value of R₀ = 10 kΩ, Gauge Factor G = 40 and Young's Modulus E = 10 MPa. Blood pressure variations results in small finite change in strain ε (ε > 0).
If V₀ is the output voltage of the Wheatstone bridge and σ is the stress in MPa, the sensitivity V₀/σ is ______ V.MPa⁻¹.

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9

2023 · Biomedical Engineering · Sensors and Bioinstrumentation · Sensors and Signal Conditioning

Biomedical Engineering (BM) 2023

The resistance of a thermistor is 1 k\( \Omega \) at 25 \( ^\circ \)C and 500 \( \Omega \) at 50 \( ^\circ \)C. Find the temperature coefficient of resistance (in units of \( ^\circ \)C\( ^{-1} \)) at 35 \( ^\circ \)C. (Round off the answer to three decimal places.)

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10

2023 · Biomedical Engineering · Sensors and Bioinstrumentation · Sensors and Signal Conditioning

Biomedical Engineering (BM) 2023

A metallic strain gauge with negligible piezoresistive effect is subjected to a strain of \( 50 \times 10^{-6} \). For the metal, Young’s Modulus = 80 GPa and Poisson’s Ratio = 0.42. What is the change in resistance (in m\( \Omega \)), if the unstrained resistance of the strain gauge is 200 \( \Omega \) ? (Round off the answer to one decimal place.)

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11

2023 · Biomedical Engineering · Sensors and Bioinstrumentation · Sensors and Signal Conditioning

Biomedical Engineering (BM) 2023

A Wheatstone bridge strain gauge transducer is constructed on a diaphragm in such a way that when a force is applied on the diaphragm, the resistors \( R_1 \) and \( R_4 \) will be in compression, and the resistors \( R_2 \) and \( R_3 \) will be in tension.
The bridge excitation voltage (\( E_{in} \)) is 10 Volts. If all the resistors have a resistance of \( 200 \ \Omega \) in the absence of any force, and each resistance changes by \( 20 \ \Omega \) upon application of a force, what is the output voltage \( V_{out} \) (in Volts) from the Wheatstone bridge? (Round off your answer to the nearest integer.)

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12

2025 · Biomedical Engineering · Sensors and Bioinstrumentation · Sensors and Signal Conditioning

Biomedical Engineering (BM) 2025

Consider two cuboidal blocks of volume 1 cm³ each, one made of gold and the other of undoped silicon. What will happen to the resistivity of these blocks if the temperature is increased from 300 K to 350 K? Choose one of the following.

A

Resistivity of gold increases and undoped silicon decreases

B

Resistivity of gold decreases and undoped silicon increases

C

Resistivity of gold remains same and undoped silicon increases

D

Resistivity of gold decreases and undoped silicon remains same

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13

2025 · Biomedical Engineering · Sensors and Bioinstrumentation · Sensors and Signal Conditioning

Biomedical Engineering (BM) 2025

Which one of the following does NOT use piezoelectric transducers?

A

Ultrasonography

B

Phonocardiography

C

Echocardiography

D

Electroencephalography

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14

2025 · Biomedical Engineering · Sensors and Bioinstrumentation · Sensors and Signal Conditioning

Biomedical Engineering (BM) 2025

Which of the following statement(s) about pulse oximetry is/are TRUE?

A

Oxygenated hemoglobin absorbs less infrared light (900 nm) compared to deoxygenated hemoglobin

B

Oxygenated hemoglobin absorbs less visible light (600 nm) compared to deoxygenated hemoglobin

C

Oxygenated hemoglobin absorbs more visible light (600 nm) compared to deoxygenated hemoglobin

D

Oxygenated hemoglobin absorbs more infrared light (900 nm) compared to deoxygenated hemoglobin

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15

2025 · Biomedical Engineering · Sensors and Bioinstrumentation · Sensors and Signal Conditioning

Biomedical Engineering (BM) 2025

Resistance \(R\) of a thermistor varies as a function of temperature \(T\) such that \(R(T) = R_0 \exp[\beta(\frac{1}{T} - \frac{1}{T_0})]\) where \(\beta = 3100\) K and, \(R_0\) and \(T_0\) are positive constants.
If the relative error in measuring \(R\) is 10%, what is the relative error (in percentage) in measuring 310 K temperature? __________ (rounded off to the nearest integer)

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16

2025 · Biomedical Engineering · Sensors and Bioinstrumentation · Sensors and Signal Conditioning

Biomedical Engineering (BM) 2025

A Wheatstone bridge is used to measure strain as shown in the figure below. Initially the bridge was balanced. When a strain is applied to the resistor R_strain along its length, the output voltage V_out is 10 mV.
If R_strain is a cylindrical resistor of length l and cross-sectional area A, the magnitude of the applied strain is ______. (rounded off to two decimal places)

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17

2026 · Biomedical Engineering · Sensors and Bioinstrumentation · Sensors and Signal Conditioning

Biomedical Engineering (BM) 2026

The circuit shown below is used as an instrumentation amplifier. Among the resistors used in the input stage, the value of resistance of one of the resistors (\(R^*\)) is slightly mismatched from that of the rest of the resistors (\(R\)). Assume all operational amplifiers are ideal.
Which of the following statements is/are true?

A

The resistance mismatch introduces a gain error

B

The resistance mismatch degrades the common mode rejection ratio (CMRR)

C

The resistance mismatch introduces an offset error

D

\(V_{out}\) is not sensitive to any resistance mismatch

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18

2026 · Biomedical Engineering · Sensors and Bioinstrumentation · Sensors and Signal Conditioning

Biomedical Engineering (BM) 2026

A photodiode is in series with a \(10\ \text{k}\Omega\) resistor. A laser beam with wavelength 532 nanometer shines on this photodiode such that the entire beam is incident on its active area. The photodiode responsivity is 0.5 ampere per watt (A/W) at this wavelength. If a voltage of 10 millivolts (mV) is developed across the \(10\ \text{k}\Omega\) resistor, the laser power incident on the photodiode is __________ microwatts (\(\mu\)W).
(Round off to one decimal place).
Assume that the dark current of the photodiode is zero.

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