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Correct choice is (c) optical fiber

To explain: Fluoroptic temperature sensors work on the principle of optical fiber sensors. They contain a rare earth phosphor which is illuminated by a white light along a short LENGTH of LARGE core optical FIBRE. The light excites the phosphor which emits a number of lines. By using filters, two of these lines at 540 and 630 nm are SELECTED, and the ratio of their intensities is a single valued FUNCTION of the temperature of the phosphor.

Correct choice is (d) THRESHOLD

Explanation: The threshold of the transducer is the smallest CHANGE in MEASURANT that will RESULT in a measurable change in the transducer output. Offset is the output that will exist when it should be zero. Linearity shows closeness of a transducer’s calibration curve to a specific straight line with in a GIVEN percentage of full scale output.

Right option is (a) CONFORMANCE

To elaborate: Conformance indicates the closeness of a calibration curve to a specified curve for an inherently non linear transducer. Hysteresis ischange in output with the same value of input but with a DIFFERENT HISTORY of input variation. The region in which the output does not changes with INCREASE in input is called saturation.

The correct answer is (c) 3

The best I can EXPLAIN: Total 3 coils are required in LVDT. One centered COIL which is the energizing or primary coil connected to the sine wave oscillator. The other two coils are the SECONDARY coils so connected that their outputs are equal in magnitude but opposite in phase.

Right choice is (b) high PASS filter

The best I can explain: High pass filter AMPLIFIES signal above a certain FREQUENCY. Low pass filter amplifies signals below a certain frequency. BAND pass filter amplifies frequencies within a certain band. Band stop filter amplifies all the frequencies except those in a certain band.

Right option is (d) teflon

To explain: The monopolar needle electrode consists of a teflon coated STAINLESS steel wire. The wire is bare only at the tip. It is FOUND that after the needle has been used a number of TIMES, the teflon coating will recede, INCREASING the tip area. The needle should be discarded when this happens.

Right ANSWER is (a) chemical sensor

To elaborate: In the chemical sensors, a chemical transduction system is INTERFACED to the optical fibre at its end. In operation, INTERACTION with analyte leads to a change in optical properties of the reagent phase, which is probed and detected through the fibre OPTIC. The optical property measured can be ABSORBANCE, reflectance or luminescence.

The correct ANSWER is (b) gauge factor

The 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.

The correct option is (b) reverse biased

To elaborate: The PHOTODIODE is a P-N junction semiconductor diode. It ALWAYS operated in the reversed biased CONDITION. The light is always focused through a GLASS lens on the junction of the PHOTO diode.

The correct choice is (a) variable resistance

The explanation is: 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.

The correct option is (b) saturation

For explanation I WOULD SAY: The region in which the output does not changes with increase in input is called saturation. It is a static property of the transducer. Settling time is the time for the sensor to reach a stable output once it is TURNED on. Frequency response is the change of transfer function with frequency, both in MAGNITUDE and in phase.

Right answer is (a) biocatalytic membrane

The explanation: The biological response of the biosensor is DETERMINED by biocatalytic membrane. The biocatalytic membrane accomplishes the conversion of reactant to product. The product of the REACTION diffuses to the TRANSDUCER. This then causes the ELECTRICAL response.

Correct choice is (C) THERMAL SENSORS

Explanation: The variations in the returning light are sensed using a photodetector. Such sensors monitor variations EITHER in the amplitude or frequency of the reflected light. Two of the most important PHYSICAL parameters that can be advantageously measured using fibre optics are temperature and pressure.

The correct option is (a) True

To explain: SELENIUM cells are sensitive to almost the entire range of wavelengths of the spectrum. However, their SENSITIVITY is greater within the visible spectrum and HIGHEST in the zones near the YELLOW wavelengths.

The correct answer is (c) frequency response

For explanation I would say: Frequency response is the change of TRANSFER FUNCTION with frequency, both in magnitude and in phase. It is a dynamic property. ABILITY of the sensor to repeat a measurement when put back in the same environment is called repeatability. The region in which the output does not changes with increase in input is called saturation.

The CORRECT choice is (b) pressure

Easy 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.

The correct option is (c) three

The best I can explain: COMPENSATION for temperature variation in the leads can be provided by using threelead 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.

Correct answer is (a) DISPLACEMENT

Easy EXPLANATION: LVDT is a displacement transducer. It works on the principle of variable inductance. The SHIFT in the ferromagneticcore from the centre POSITION induces voltage in the second coild which can be calibrated to determine the linear displacement.

Correct answer is (C) OPTIC fiber sensors

The explanation: Optic sensors are USED for endoscopic imaging. Optical fibre sensors are non-electrical and hence are free from electrical interference usually ASSOCIATED with electronically based sensors. They are suitable for telemetry applications as the bulk of the instrumentation can be at a reasonable distance from the PATIENT.

Correct CHOICE is (a) True

The explanation is: Cesium-silver oxide cells are sensitive to the near INFRARED wavelengths. Potassium silver oxide and cesium-antimony cells have maximum sensitivity in the visible and ultraviolet regions. The SPECTRAL response also depends partly on the transparency to different wavelengths of the MEDIUM to be TRAVERSED by the light before reaching the cathode.

Right ANSWER is (c) gas-filled photocell

The BEST explanation: Barrier layer cells are photovoltaic cells. They consist of a semiconducting substance, which is generally selenium deposited on a METAL base which may be iron and which acts as one of the electrodes. Photovoltaic cells are very robust in construction, NEED no external electrical supply and produce a photocurrent sometimes STRONGER than other photosensitive elements.

Right option is (a) True

To explain I would SAY: The junction at a HIGHER temperature in THERMOCOUPLE is TERMED as measuring junction. The junction at lower temperature in the thermocouple is called the reference temperature. The cold junction is usually KEPT at 0^0C.

Correct OPTION is (b) span

The BEST explanation: Input RANGE is the range between the max and MIN values is applied parameter which can be measured . Ability of the sensor to REPEAT a measurement when put back in the same environment is called repeatability. The total operating range of the transducer is called span of the transducer.

The correct choice is (a) TEMPERATURE

The best explanation: Thermistor is used to measure temperature. It is a temperature TRANSDUCER. With a change in temperature its resistance changes. Thus its working principle is variable resistance. Thermistors are the oxides of certain METALS like manganese, cobalt and NICKEL which have large negative temperature COEFFICIENT, i.e. resistance decreases with increase in temperature.

Right choice is (a) quartz

Easiest explanation: Aluminium is not apiezo-electric material. Quartz is the most stable natural crystal with high mechanical and thermal stability and has voulme resistivity higher than 10^4 ohm-cm and SMALL internal electric loss. BARIUM titanate CERAMIC is a FERROELECTRIC crystal and has small voltage output.

Right answer is (b) sensitivity

The explanation: The sensitivity of the sensor is defined as the slope of the output characteristic CURVE. In simple words The minimum INPUT of physical parameter that will create a detectable out change is called sensitivity. Total operating RANGE of the transducer is called its SPAN.

The correct CHOICE is (a) True

The best explanation: Home blood GLUCOSE DETECTION SENSOR works on the PRINCIPLE of electrochemical. The biosensor in this instrument relies upon enzymes that recognize and catalyze reactions of glucose with the generation of redox – active species that are detected electrochemically.

The correct answer is (a) temperature

The best I can EXPLAIN: Thermistor is used to measure temperature. It is a temperature TRANSDUCER. With a change in temperature its resistance changes. Thus its working principle is VARIABLE resistance. Thermistors are the oxides of certain metals like MANGANESE, cobalt and nickel which have large NEGATIVE temperature coefficient, i.e. resistance decreases with increase in temperature.

Right choice is (b) False

To explain: Photovoltaic cells are very ROBUST in construction, need no external ELECTRICAL supply and produce a photocurrent sometimes stronger than other photosensitive elements. TYPICAL photocurrents produced by these cells are as high as 120 mA/lumen. At constant temperature, the current SET up in the cell usually shows a linear relationship with the incident light intensity.

Correct choice is (B) False

Best 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.

Correct OPTION is (b) microvolts

The best explanation: The signals of interest in medical RECORDERS are in the RANGE of micro volts. They are captured by the help of sensitive electrodes and transducers and then amplified to a certain higher LEVEL. After the amplification further PROCESSING is carried out.

The CORRECT option is (b) False

To explain: The CENTER coil is the energizing or PRIMARY coil CONNECTED to a sine wave oscillator. The secondary coils so connected that their outputs are equal in magnitude but opposite in phase. LVDT works on the principle of variable inductance.

The CORRECT choice is (d) drift

Explanation: Drift INDICATED a change of BASE line or of sensitivity with time, temperature etc. Drift is BASICALLY the change in a signal over long period of time. Noise is the unwanted signal at the output due either to internal sources or to interference. Offset is the output that will exist when it should be ZERO.

The correct option is (a) resolution

The BEST I can explain: The ability of the sensor to see small differences in reading is called the resolution of the sensor. Offset is the output that will exist when it should be ZERO. Linearity shows CLOSENESS os a transducer’s calibration curve to a specific straight LINE with in a given percentage of full SCALE output.

Correct answer is (a) photomultiplier tubes

To explain I would say: Photomultiplier tubes are photoemissive cells.These type to cells do require an external power supply to provide a sufficient potential DIFFERENCE between the ELECTRODES to facilitate the flow of electrons generated at the photosensitive CATHODE surface. Also, amplifier CIRCUITS are invariably employed for the amplification of this CURRENT.

Correct choice is (c) ambient light interference

To explain: Optical FIBRE sensors are non-ELECTRICAL and hence are FREE from electrical interference usually associated with electronically based sensors. Ambient light can interfere. Consequently, the sensor has to be applied in a dark environment or must be optically isolated.

The CORRECT choice is (b) False

For explanation: The junction at a lower temperature in the THERMOCOUPLE is called the REFERENCE temperature. The cold junction is usually KEPT at 0^0C. The junction at a HIGHER temperature in thermocouple is termed as measuring junction.

Correct OPTION is (d) saturation

The explanation: The region in which the output does not changes with INCREASE in input is called saturation. The threshold of the transducer is the smallest change in measurant that will result in a measurable change in the transducer output. Offset is the output that will EXIST when it should be zero.

The CORRECT choice is (B) LVDT

The explanation is: LVDT is a displacement transducer. THERMOCOUPLE and thermistor are temperature transducers. STRAIN GAUGE is a pressure transducer.