25-04-2014, 03:38 PM
BIO-MEDICAL INSTRUMENTATION Two marks Questions and Answers
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1.Define a transducer.
A transducer is a device which when activated by energy in one transmission system,supplies energy in the another form to a second transmission system.
This energy transmission may be electrical ,mechanical, chemical , optical(radiant) or thermal.
2.How transducers are classified?
Transducers are classified according to their application,method of energy conversions and nature of the output signal.
3. Name the types of Resistance transducers.
Potentiometric device,resistance strain gauge,resistance thermometer and photoconductive cell.
4. Name the capacitance transducers.
Variable capacitance pressure guage,capacitor microphone and dielectric guage.
5. Name the types of inductance transducers.
Magnetic circuit transducer,reluctance pick up,differential transformer,eddy current gage and magnetostriction gage.
6. Mention the various resistance materials used in resistance transducers.
Constantan,nichrome,dynaloy,stability and platinum-tungsten alloys.
7. Mention the static characteristics of the transducers.
Accuracy,precision,resolution,sensitivity,drift,linearity,saturation ,noise,hysteresis
8. What is meant by resolution of a transducer?
It represents the static characteristics of a transducer.It indicates the smallest measurable input increment.
9. Write the important parameter which describes the dynamic performance of a transducer.
Response time
10. List some of the characteristics which determines the performance and choice of a transducer
input and output impedance,overload range , recovery time after overload, excitation voltage , reliability , size and weight
11. Give an example for a zero-order system transducer.
A linear potentiometer used as a displacement transducer is an example for a zero-order trasducer, since the output is proportional to the input for all frequencies and there is no amplitude or phase distortion.
12. List some of the piezo electric crystals used in piezoelectric transducers.
Quartz,tourmaline,ammonium dihydrogen phosphate, Rochelle salt, lithium sulphate ,lead zirconate, barium titanate.
13. Name the application of piezo-electrical transducers in the medical field.
They are used in ultrasonic scanners for imaging and blood flow measurements,
They are used in the detection of korottkoff sounds in non-invasive blood pressure measurements.
They are used in external and internal phonocardiography.
14. How optical transducers are used to measure the position and motion of the organs and tissues of the body?
An optical fibre can be used to detect displacement by measuring the transmitted light intensity or phase difference between the measuring beam and a reference beam. Both amplitude and position of the transmitted and reflected light can be used to measure displacement.
15. Static the basic principles of pressure transducers.
In the pressure transducers the pressure to be measured is applied to a flexible diaphragm which gets deformed by the action of the pressure exerted on it. This motion of the diaphragm is then measured in terms of an electrical signal.
16. List the various diaphragm materials used in pressure transducers.
Stainless steel, phosphor bronze, beryllium copper.
17. Name the commonly employed pressure transducers.
Capacitance manometer, differential transformer , strain guage
18. What are linistors?
Thermistors which provide a linear change in resistance with a change in temperature are called as linistors.
19. Where pressure transducers are used in medical field?
To measure blood pressure
20. To measure body temperature what type of transducers are used.
Thermistors,thermocouple
21. State the basic principle of photoelectric transducers.
Photoelectric transducers are based on the principle of conversion of light energy into electrical energy.This is done by causing the radiation to fall on a photosensitive element and measuring the electrical current so generated with a sensitive galvanometer directly or after suitable amplification.
22. Name the types of photoelectric cells.
Photovoltaic cells (barrier layer cells) and photoemissive cells.
23. Mention the applications of optical fibre transducers in the medical field.
This is used to measure physical parameters such as temperature, pressure and displacement .Used in endoscopy .Used as the delivery system for light in LASER surgery.
24. List any 2 advantages of optical fibre sensors.
They are non-electrical and hence are free from electrical interference usually associated with electronically based sensors.
They do not involve any electrical connection to the patient body,thereby ensuring patient safety.
25. Name the various types of optical fibre transducers.
Photometric transducers ,physical transducers and chemical transducers.
26.What is the function of signal conditioner in the biomedical instrumentation system?
The signal conditioner converts the output of the electrode into an electrical quantity suitable for operating the writing system in the biomedical instrumentation system.
26. List the important functions performed by the signal conditioners before the signal is given to display or recording device.
Signal amplification.frequency response ,filtering, isolation , excitation and linearization.
27. Mention the transducers having a non-linear response to changes in the phenomenon being measured?
Thermocouple,thermistors
28. State the operating requirement satisfied by the amplifiers in the signal conditioning systems.
Input impedance ,gain and frequency response characteristics.
29. What is meant by drift in the amplifier operating characteristics?
The drift is a slow change of output having no relation with a input signal applied to the amplifier.
30. What are DC amplifiers?
They are generally of the negative feedback type and are used for medium gain applications dowm to about 1mv signal levels for full scale.They are not practical for very low level applications because of dc drift and poor CMRR capabilities.They are usually employed as pen drive amplifiers in direct writing recorders.
31. List the typical examples of signals whose measurement requires the use of differential amplifiers.
Heat-generated voltages picked up by means of electrodes on the arms and legs and brain-generated voltages picked up by the electrodes on the scalp are the typical examples of signals.
32. Where differential amplifiers are employed?
They are employed when current is necessary to measure the voltage difference between 2 points both of them varying in amplitude at different rates and in different patterns.
33. State the limitations of differential amplifiers in the application of biomedical measurements.
The amplifier has a limited input impedance and therefore draws some current from the signal source and loads them to some extent.The CMRR of the amplifier may not exceed 60 db in most of the cases,which is usually inadequate in modern biomedical instrumentation systems.
34. What are the advantages of instrumentation amplifier applied in the biomedical field?
Extremely high input impedance,low bias and offset currents,less performance deterioration if source impedance changes possibility of independent reference levels for source and amplifier,very high CMRR, high slew rate and low power consumption.
35. What is meant by an instrumentation amplifier?
An instrumentation amplifier is a precision differential voltage gain device that is optimized for operation in an environment hostile to precision measurements.It consists of 3 op-amps and seven resistors.
36. Mention the various methods used in the design of isolation amplifiers.
Transformer isolation,opyical isolation and capacitive isolation.
37. What is the use of notch filter in the signal conditioning system?
To filter the 50 HZ noise from mains.
38. State the most and commonly used amplifier in biomedical applications.
Differential amplifier.
39.What information is provided by electrocardiograph?
ECG provides valuable information about a wide range of cardiac disorders such as the presence of an inactive part (infarction) or an enlargement (cardiac hypertrophy) of the heart muscle.
40 State the sensitivity rate of ECG.
10mm/mv
41. Specify the characteristics of ECG preamplifier.
ECG preamplifier is usually a 3 or 4 stage differential amplifier having a large negative current feedback and gives a stabilizing effect.
42. List the important parts of an ECG recorder.
Lead selector,ECG electrodes,preamplifier ,power amplifier , frequency selective feedback network, auxiliary circuit and pen motor.
43. Mention the lead configurations used in ECG.
Bipolar leads(einthoven leads) , unipolar leads and unipolar precordial leads.
44. Stress ECG helps to diagonise which disease.
Cardiac disorders,coronary care units and for routine diagonostic applications in cardiology.
45. What is Einthoven triangle?
It is the triangle in which the electric field of the heart is represented diagrammatically.The sides of the triangle represent the lines along which the 3 projections of the ECG vector are measured.
46. What is ECG?
ECG is an instrument which records the electrical activity of the heart.