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Sensors > Ch 4: Temperature Sensors > Flashcards

Ch 4: Temperature Sensors Flashcards

1
Q

Q: What is a thermocouple?

A

A: A sensor that measures temperature using the voltage generated by two dissimilar metals.

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2
Q

Q: Define a thermistor.

A

A: A temperature-sensitive resistor whose resistance changes with temperature.

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3
Q

Q: What is a diode temperature sensor?

A

A: A sensor that measures temperature based on the voltage across a forward-biased diode.

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4
Q

Q: What is a transistor temperature sensor?

A

A: A sensor using a transistor’s temperature-dependent voltage drop to measure temperature.

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5
Q

Q: What is the advantage of using a thermistor?

A

A: High sensitivity to temperature changes./thermistors are essentially a single-piece resistor

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6
Q

Q: What is the disadvantage of thermocouples?

A

A: Nonlinear output requiring compensation.

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7
Q

Q: What is a platinum resistance thermometer (PRT)?

A

A: A sensor using platinum to measure temperature due to its stable resistance-temperature relationship.

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8
Q

Q: How does ambient temperature affect sensors?

A

A: It can alter sensor accuracy and response time.

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9
Q

Q: What is a temperature coefficient?

A

A: The rate of change of resistance with temperature.

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10
Q

Q: What is a bimetallic strip?

A

A: A mechanical sensor that bends with temperature changes due to different expansion rates of metals.

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11
Q

Q: How is temperature measured with infrared sensors?

A

A: By detecting emitted infrared radiation from an object.

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12
Q

Q: What is self-heating in thermistors?

A

A: Heat generated by current passing through the thermistor, affecting its reading.

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13
Q

Q: What is the Seebeck effect?

A

A: The generation of voltage due to temperature differences across a conductor.

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13
Q

Q: What is a resistance temperature detector (RTD)?

An RTD (Resistance Temperature Detector

A

A: A sensor that measures temperature based on the resistance change in a metal.

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14
Q

Q: What is the purpose of a temperature sensor in HVAC systems?

A

A: To regulate and maintain desired temperature levels.

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14
Q

Q: Why are thermistors nonlinear?

A

A: Because their resistance-temperature relationship is exponential.

15
Q

Q: How is a thermocouple calibrated?

A

A: By comparing its readings against a known temperature standard.

16
Q

Q: What is the main advantage of RTDs?

RTD (Resistance Temperature Detector)

A

A: High accuracy and stability over a wide temperature range.

16
Q

Q: What is the temperature range of PRTs?

A

A: Typically -200°C to 850°C.

17
Q

Q: What is the response time of a temperature sensor?

A

A: The time it takes to reach a stable output when temperature changes.

18
Q

Q: How does an analog temperature sensor work?

A

A: It converts temperature into an analog voltage signal.

19
Q

Q: What are NTC thermistors?

(NTC Thermistors )

A

A: Negative Temperature Coefficient thermistors, where resistance decreases with temperature increase.

20
Q

Q: What are PTC thermistors?

A

A: Positive Temperature Coefficient thermistors, where resistance increases with temperature increase.

21
Q

Q: What is a thermal couple junction?

A

A: The point where two metals in a thermocouple are joined.

22
Q

Q: What is the advantage of digital temperature sensors?

A

A: They provide direct digital output without additional circuitry.

23
Q

Q: How does a Zener diode temperature sensor behave when held with human fingers?

A

A: the voltage reach an stability at finger tem.

24
Q

Q: What is the expected voltage of an LM335 Zener diode at 298 K?

A

A: +2.98 V.

25
Q

Q: What is the main advantage of Zener diodes over thermistors?

A

A: Stability and linearity in voltage output.

26
Q

Q: What happens to a Zener diode sensor’s output when improperly cooled?

A

A: It provides inaccurate readings due to uncontrolled self-heating or heat dissipation.

Sensors (14 decks)

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