# Biomedical Instrumentation Questions and Answers – Transducers for Body Temperature Measurement

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This set of Biomedical Instrumentation Interview Questions and Answers for freshers focuses on “Transducers for Body Temperature Measurement”.

1. Sudden involuntary drop in body core temperature below 35*C (95*F) is called __________
a) Accidental hyperthermia
b) Accidental misothermia
c) Accidental exothermia
d) Accidental hypothermia

Explanation: Sudden involuntary drop in body core temperature below 35*C (95*F) is called Accidental hypothermia. In this, the body temperature drops very quickly. If not treated on time can lead to patients death.

2. Which of the following has the widest range of temperature measurement?
a) RTD
b) Thermocouple
c) Thermistor
d) Mercury thermometer

Explanation: Thermocouple has the widest range of temperature measurement from -1840C to +23000C. RTD has a range of -2000C to +8500C. Thermistor has a range of 00C to 1000C where as conventional mercury thermometers range is -370C to +3560C.

3. The junction at a higher temperature in thermocouple is termed as measuring junction.
a) True
b) False

Explanation: 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 00C.
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4. When two wires of different material are joined together at either end, forming two junctions which are maintained at a different temperature, a thermo-motive force is generated causing a current to flow around the circuit. This arrangement is called ___________
a) thermal pair
b) thermistor
c) thermocouple
d) thermostat

Explanation: This arrangement is called thermocouple. 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.

5. When two wires of different material are joined together at either end, forming two junctions which are maintained at a different temperature, a _________ force is generated.
a) thermo-motive
b) electro-motive
c) chemical reactive
d) mechanical

Explanation: When two wires of different material are joined together at either end, forming two junctions which are maintained at a different temperature, a thermo-motive force is generated causing a current to flow around the circuit. This arrangement is called thermocouple. The junction at higher temperature in thermocouple is termed as measuring junction. The junction at lower temperature in the thermocouple is called the reference temperature.

6. The junction at a lower temperature in the thermocouple called measuring junction.
a) True
b) False

Explanation: The junction at a lower temperature in the thermocouple is called the reference temperature. The cold junction is usually kept at 00C. The junction at a higher temperature in thermocouple is termed as measuring junction.

7. The lower temperature junction in thermocouple is maintained at ________
a) -273 K
b) 0 K
c) -327 K
d) 273 K

Explanation: The lower temperature junction in thermocouple is maintained at 273 K (00C). The junction at lower temperature in the thermocouple is called the reference temperature. The junction at higher temperature in thermocouple is termed as measuring junction.

8. The resistance Rt of a metallic conductor at any temperature t is given by ___________
a) Rt = Ro(1+ɑt)
b) Rt = Ro(1-ɑt)
c) Rt = Ro(ɑt-1)
d) Rt = Ro(10+ɑt)

Explanation: The resistance Rt of a metallic conductor at any temperature t is given by Rt = Ro(1+ɑt). Ro is the resistance at 0*C. ɑ is temperature coefficient of resistivity.

9. RTD stands for ________
a) resistance temperature device
b) resistance temperature detector
c) reluctance thermal device
d) resistive thermal detector

Explanation: RTD stands for Resistance Temperature Device. It is a passive sensor and requires current excitation to produce an output voltage. RTD has very low temperature coefficient. Voltage drop across RTD is much larger than thermocouple output voltage.

10. Thermister is used to measure _____________
a) temperature
b) pressure
c) height
d) displacement

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.

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