History of Temperature Measurement

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Questions and Answers

What is the minimum theoretically reachable temperature known as?

Thermal equilibrium

Liquid nitrogen

Absolute zero (correct)

Freezing point

What was invented by Galileo Galilei in 1592?

Liquid-in-glass thermometer (correct)

Resistance Temperature Detector

Liquefied gas thermometer

Thermocouple

Which principle does a thermocouple rely on?

Absorption of light

Conduction of metals

Centrifugal force

Thermoelectric current (correct)

Which term describes the process of measuring local temperature?

Thermometry Signup and view all the answers

How does increased temperature affect molecular motion?

It increases the kinetic energy of particles Signup and view all the answers

What process describes the movement of heat in a fluid due to density differences?

Convection Signup and view all the answers

Who invented the first mercury thermometer?

Athanasius Kircher Signup and view all the answers

What is the primary function of bistate/phase change sensors?

To indicate color changes at specific temperatures Signup and view all the answers

Which temperature range do mercury-filled systems operate within?

-40 °C to 650 °C Signup and view all the answers

What does a thermocouple use to measure temperature?

The difference in voltage between two dissimilar metals Signup and view all the answers

Which effect is NOT associated with a thermocouple?

Lenz's Effect Signup and view all the answers

What is the response time typical for bistate/phase change sensors?

Minutes and may not respond to transient changes Signup and view all the answers

How does the Seebeck voltage in a thermocouple get produced?

By the difference in temperature at two metal junctions Signup and view all the answers

What material forms the basis of bistate/phase change sensors?

Fusible crystalline solids Signup and view all the answers

What is a major use of temperature labels or stickers?

To record if an object has exceeded a specific temperature Signup and view all the answers

What is the primary method of energy transfer to the surface mentioned in the content?

Convection Signup and view all the answers

At what temperature range is mercury a liquid?

−40 to 700°F Signup and view all the answers

Which type of thermometer uses a bimetallic element?

Bimetallic Thermometers Signup and view all the answers

What is the purpose of bonding two strips of dissimilar metals in a bimetal strip?

To amplify bending motion Signup and view all the answers

What range of temperatures can filled-bulb systems measure?

−125 to 1200°F Signup and view all the answers

What is the main reason for the decline in the use of mercury-in-glass thermometers?

Toxicity of mercury Signup and view all the answers

In what year was the International Practical Temperature Scale first established?

1948 Signup and view all the answers

What principle does a filled-bulb thermometer exploit to measure temperature?

Fluid expansion Signup and view all the answers

What is the resistance of the RTD element at 0° C?

100 Ω Signup and view all the answers

What kind of materials are RTDs typically made of?

Pure metals such as platinum or copper Signup and view all the answers

What is a major difference between thermistors and RTDs?

Thermistors can either increase or decrease in resistance with temperature. Signup and view all the answers

What is the primary function of a pyrometer?

To measure temperature from radiation without contact Signup and view all the answers

What distinguishes radiation pyrometers from optical pyrometers?

Radiation pyrometers utilize infrared energy detection. Signup and view all the answers

What is a common application of pyrometers?

To measure extremely high temperatures above 1500°C Signup and view all the answers

Which law explains the energy broadcasting of thermal radiation?

Planck’s Law of Thermal Radiation Signup and view all the answers

How does the resistance change with temperature in a thermistor?

It varies significantly depending on the type of thermistor. Signup and view all the answers

What is the primary function of the detector in an optical pyrometer?

To convert heat energy into an electrical signal Signup and view all the answers

How does an observer determine the temperature using an optical pyrometer?

By adjusting a rheostat until the reference lamp brightness matches the source Signup and view all the answers

What happens when the filament of the reference lamp disappears during measurement?

There is equal brightness between the filament and temperature source Signup and view all the answers

What characteristic of thermocouples makes them less accurate compared to RTDs?

They lack stability and precision Signup and view all the answers

What are RTDs known for in terms of performance?

Stability and relatively wide temperature range Signup and view all the answers

How does the optical pyrometer measure temperature through the brightness comparison?

By comparing the thermal radiation emitted by the object and lamp Signup and view all the answers

Which of the following describes a limitation of mechanical temperature measuring devices?

They are limited in application due to construction and temperature range Signup and view all the answers

What is a common method of observing changes in current in reference lamps of pyrometers?

Visual monitoring of filament brightness Signup and view all the answers

Study Notes

Temperature Measurement

Temperature measures the average kinetic energy of particles; it's the primary indicator of how hot or cold something is.
Absolute zero (-273.15°C or 0 K) is the theoretical minimum temperature where molecular motion ceases.
Temperature measurements significantly influence various physical, chemical, and biological processes.

Historical Milestones in Temperature Measurement

1592: Galileo Galilei invented the liquid-in-glass thermometer.
1643: Athanasius Kircher created the first mercury thermometer.
1714: Daniel Gabriel Fahrenheit developed both mercury and alcohol thermometers using the Fahrenheit scale.
1742: Anders Celsius proposed the centigrade (Celsius) scale.
1800s: William Thomson (Lord Kelvin) suggested the notion of absolute zero.
1821: Thomas Seebeck discovered thermoelectric current principles and thermocouples.
1821: Sir Humphry Davy noted temperature effects on metals.
1932: C.H. Meyers built the first Resistance Temperature Detector (RTD).
1948: The term "centigrade" was officially changed to "Celsius."

Methods of Temperature Measurement

Temperature measurement methods include thermometers, probes, and non-contact sensors.

Heat Transfer Mechanisms

Conduction: Heat transfer through a material due to temperature difference without material movement.
Convection: Heat transfer in fluids caused by the movement of warmer, less dense areas rising and cooler, denser areas sinking.
Radiation: Energy emission through electromagnetic waves, including high-energy particles causing ionization.

International Practical Temperature Scale

Established by an international commission in 1948, with revisions in 1960 and 1990, forming the basis for current temperature measurements.

Types of Temperature Sensors

Liquid-in-Glass Thermometers: Historically used mercury; effective from -40°F to 700°F. Mercury's toxicity limits modern usage.
Bimetallic Thermometers: Utilize dissimilar metals to create mechanical bending motion that drives a pointer, operational from -73 to 537°C.
Filled-bulb Systems: Rely on fluid expansion, suitable for -125°F to 1200°F.
Phase Change Sensors: Non-electric sensors that change appearance or color at specific temperatures, useful for low-cost applications.

Electronic Temperature Sensors

Thermocouples: Combine two different metals to produce a voltage proportional to temperature difference. Utilize Seebeck effect principles.
RTDs: Use pure metals (like platinum) whose resistance increases linearly with temperature; commonly specified at 100 Ω at 0°C.
Thermistors: High sensitivity devices that change resistance with temperature, available in positive or negative temperature coefficients.

Non-contact Thermometry

Pyrometers: Measure temperature from thermal radiation emitted by objects, effective above 1500°C.
- Radiation Pyrometers: Use infrared radiation detection; based on Planck’s Law of Thermal Radiation.
- Optical Pyrometers: Compare brightness of a hot object to a calibrated source bulb, utilizing human eye perception for temperature measurement.

General Comparisons of Sensors

Thermocouples: Wide range, rugged but less stable than RTDs.
RTDs: Stable and relatively wide range but less rugged and more expensive.
Thermistors: Highly sensitive with notable resistance changes but linearity issues compared to RTDs.

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Description

Explore the fascinating milestones in the development of temperature measurement. From Galileo's first thermometer to the establishment of the Celsius and Fahrenheit scales, this quiz covers key historical advancements. Test your knowledge on how these innovations have influenced scientific understanding of temperature.