Biomedical Instrumentation Questions and Answers – Pressure Transducers

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This set of Biomedical Instrumentation Multiple Choice Questions & Answers (MCQs) focuses on “Pressure Transducers”.

1. Which of the following is not a piezo-electric material?
a) quartz
b) rochelle salt
c) aluminium
d) barium titanate
View Answer

Answer: c
Explanation: Aluminium is not a piezo-electric material. Quartz is the most stable natural crystal with high mechanical and thermal stability and has voulme resistivity higher than 104 ohm-cm and small internal electric loss. Barium titanate ceramic is a ferroelectric crystal and has small voltage output.
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2. Piezo-electricity is ______________
a) sound electricity
b) pressure electricity
c) temperature electricity
d) photo electricity
View Answer

Answer: b
Explanation: Piezo-electricity is pressure electricity. The piezo electric effect is a property of natural crystalline substance to develop electric potential along a crystallographic axis in response to the movement of charge as a result of mechanical deformation.

3. On applying electricity to piezo-electric material mechanical deformation occurs in the material.
a) True
b) False
View Answer

Answer: a
Explanation: Yes, on applying electricity to the piezo-electric material mechanical deformation occurs in the material. The piezo electric effect is a property of natural crystalline substance to develop electric potential along a crystallographic axis in response to the movement of charge as a result of mechanical deformation.
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4. Which of the following is a material employed making diaphragm to measure pressure?
a) tourmaline
b) barium titanate
c) phosphor bronze
d) zirconate titanate
View Answer

Answer: c
Explanation: Phosphor bronze is used to make diaphragm to measure pressure. The motion of diaphragm is measured in terms of electric signals. Tourmaline , barium titanate and zirconate titanate are piezo electric materials.

5. Principle behind strain gauge is _____________
a) variable resistance
b) variable inductance
c) variable capacitance
d) variable contact area
View Answer

Answer: a
Explanation: The principle behind strain gaude is the variable resistance. The transducer is based upon the changed in resistance of a wire produced due to small mechanical displacement. A linear relation exists between the deformation and electrical resistance of a suitable selected gauge over a specified range.
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6. On applying pressure to piezo-electric crystal, electricity is not generated.
a) True
b) False
View Answer

Answer: b
Explanation: On applying pressure to piezo-electric crystal, electricity is generated. The piezo electric effect is a property of natural crystalline substance to develop electric potential along a crystallographic axis in response to the movement of charge as a result of mechanical deformation. Thus, piezo-electricity is pressure electricity.

7. The figure of merit which describes the overall behaviour of the wire under stress is determined from?
a) elastic modulus
b) gauge factor
c) elastic factor
d) gauge resistance
View Answer

Answer: b
Explanation: The figure of merit which describes the overall behaviour of the wire under stress is determined from the gauge factor of the wire. Gauge factor gives information on the expected resistance change or output signal at maximum permissible elongation.the gauge factor determines to a large extent the sensitivity of the wire when it is made into a practical strain gauge.
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8. Gauge factor is defined as _______________
a) (incremental change in resistance due to stress/resistance of an unstretched wire)*(unstretched length of wire/incremental change in length)
b) (incremental change in resistance due to strain/resistance of an unstretched wire)*(unstretched length of wire/incremental change in length)
c) (incremental change in resistance due to stress/resistance of an unstretched wire)*(incremental change in length/unstretched length of wire)
d) (resistance of an unstretched wire/incremental change in resistance due to stress)*(unstretched length of wire/incremental change in length)l
View Answer

Answer: a
Explanation: Gauge factor is defined as (incremental change in resistance due to stress/resistance of an unstretched wire)*(unstretched length of wire/incremental change in length). Gauge factor gives information on the expected resistance change or output signal at maximum permissible elongation.the gauge factor determines to a large extent the sensitivity of the wire when it is made into a practical strain gauge.

9. Compensation for temperature variation in the leads can be provided by using ________ lead method.
a) six
b) four
c) three
d) two
View Answer

Answer: c
Explanation: Compensation for temperature variation in the leads can be provided by using three lead method. In this method two of the leads are in the adjacent legs of the bridge which cancels their resistance changes and does not disturb the bridge balance. The third lead is in series with the power supply and is therefore independent of bridge balance.
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10. Strain gauge is used to measure ______________
a) temperature
b) pressure
c) height
d) displacement
View Answer

Answer: b
Explanation: Strain gauge is used to measure pressure. Its working principle is change in resistance. There are two type of strain gauges. Bounded strain gauge and unbounded strain gauge. Mostly used to measure the arterial and venous blood pressure in the body.

Sanfoundry Global Education & Learning Series – Biomedical Instrumentation.

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Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He is Linux Kernel Developer & SAN Architect and is passionate about competency developments in these areas. He lives in Bangalore and delivers focused training sessions to IT professionals in Linux Kernel, Linux Debugging, Linux Device Drivers, Linux Networking, Linux Storage, Advanced C Programming, SAN Storage Technologies, SCSI Internals & Storage Protocols such as iSCSI & Fiber Channel. Stay connected with him @ LinkedIn | Youtube | Instagram | Facebook | Twitter