Biomedical Instrumentation Multiple Choice Questions on “Single Channel Telemetry System”.
1. ___________ system may include lenses, mirrors, slits, diaphragm etc.
a) Photo system
b) Radiant system
c) Cardiac system
d) Optical system
Answer: d
Clarification: A detecting system for the measurement of unabsorbed radiant energy, which could be the human eye, a barrier-layer cell, phototube or photo-multiplier tube. An optical system for producing a parallel beam of filtered light for passage through an absorption cell (cuvette). The system may include lenses, mirrors, slits, diaphragm, etc.
2. __________ is not the property of instrumentational amplifier.
a) Extremely high input impedance
b) Very low CMRR
c) Low bias and offset currents
d) High slew rate
Answer: b
Clarification: Instrumentational amplifiers have very high CMRR. The instrumentation amplifier offers the following advantages for its applications in the biomedical field. Some of them are like extremely high input impedance, low bias and offset currents, high slew rate.
3. Which of the following feedback type is employed with DC amplifiers?
a) negative
b) can be any positive or negative doesn’t matter
c) depends on the application
d) positive
Answer: a
Clarification: DC amplifiers are generally of the negative feedback type. They are used for medium gain applications down to about 1 mV signal levels for full scale. They are not practical for very low level applications because of dc drift and poor common-mode rejection capabilities.
4. The CMRR is expressed in _____________
a) V/s
b) dB/ms
c) dB/s
d) dB
Answer: d
Clarification: The ability of the amplifier to reject common voltages on its two input leads is known as common-mode rejection. It is specified as the ratio of common-mode input to differential input to elicit the same response. CMRR is an important specification referred to the differential amplifier and is normally expressed as decibels.
5. An oscillator and a capacitance coupled amplifier are present in a carrier amplifier.
a) True
b) False
Answer: a
Clarification: It is True. The transducers, which require ac excitation, are those whose impedance is not purely resistive. The carrier amplifier consists of an oscillator and a capacitance coupled amplifier. The oscillator is used to energize the transducer with an alternating carrier voltage.
6. Reduction in electromagnetic coupling is achieved by _____
a) shielding
b) common grounding
c) multiple grounding
d) wire twisting
Answer: c
Clarification: Electromagnetic coupling is reduced by shielding, wire twisting and proper grounding which provide a balanced signal pair with satisfactory noise rejection characteristics. Having multiple grounds in a single circuit increases the electromagnetic coupling effect by producing ground loop which may generate so much noise that it may completely obscure the useful signal.
7. ________________ is employed with resistive transducers which require an external source of excitation?
a) dc bridge amplifier
b) ac coupled amplifier
c) carrier amplifier
d) differential amplifier
Answer: a
Clarification: Essentially, the amplifier comprises a stable dc excitation source, a bridge balance and calibration unit, a high gain differential dc amplifier and a dc output amplifier. DC bridge amplifiers are employed with resistive transducers which require an external source of excitation. They can be used as conventional dc high gain amplifiers and offer operating simplicity and high frequency response.
8. From the options given below select the one which is not a type of isolation amplifier?
a) transformer type isolation amplifiers
b) resistive coupled isolation amplifiers
c) optically isolated isolation amplifiers
d) capactively coupled isolation amplifiers
Answer: b
Clarification: Opto-coupled amplifier uses a minimum number of components and is cost effective, followed by the transformer coupled amplifier. The capacitor coupled amplifier is the most expensive. There is nothing such as the resistive coupled isolation amplifiers. All the other three types are in common use, though the transformer isolation amplifier is more popular.
9. The isolation includes common supply voltage sources and common grounds on each side of the isolation barrier.
a) True
b) False
Answer: b
Clarification: It is False. Three methods are used in the design of isolation amplifiers: (i) transformer isolation (ii) optical isolation (iii) capacitive isolation. Isolation amplifiers are commonly used for providing protection against leakage currents. The isolation includes different supply voltage sources and different grounds on each side of the isolation barrier.
10. Which of the following amplifier is commonly used for providing protection against leakage currents?
a) Isolation amplifiers
b) Instrumentational amplifiers
c) Inverting amplifiers
d) Differential amplifiers
Answer: a
Clarification: Isolation amplifiers are commonly used for providing protection against leakage currents. They break the ohmic continuity of electric signals between the input and output of the amplifier. The isolation includes different supply voltage sources and different grounds on each side of the isolation barrier.