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foreword
This article mainly explains the relevant knowledge of temperature sensitive sensors
1. Temperature scale
(1) Definition
(2) Conversion
Celsius
摄氏度=5(华氏度-32)/9
摄氏度=开氏度-273.15
摄氏度=5兰氏度/9-273.15
摄氏度=1.25列氏度
Fahrenheit
华氏度= 1.8摄氏度+32
华氏度= 1.8开氏度-459.67
华氏度=兰氏度-459.67
华氏度=2.25列氏度+32
Kelvin
开氏度=摄氏度+273.15
开氏度= 1.25列氏度+273.15
开氏度= 5(华氏度-32)/9 +273.15
开氏度= 5兰氏度/9
2. Concepts related to thermodynamics
(1) Heat flux
The amount of heat flowing through a unit area per unit time.
(2) Thermal conductivity
The ability of a material to conduct heat directly is called thermal conductivity
Thermal conductivity is defined as the heat directly conducted by a material per unit cross-section and unit length under unit temperature difference and unit time .
The unit of thermal conductivity is watts per meter per Kelvin (W/mK)
(3) heat capacity
It is a parameter that measures the heat energy that can be contained in an object, similar to capacitance.
==Heat capacity is when a substance absorbs heat and its temperature rises, the heat absorbed for every 1K increase in temperature is called the heat capacity of the substance. == In the general physical sense, the heat required to increase the temperature of the system by 1K is called the heat capacity of the system (symbol C, unit J/K). It is defined as the amount of heat required to raise an object by one degree.
(4) calories
Defined as the heat required to raise 1 gram of water from 14.5°C to 15.5°C.
Imperial: BTU is defined as the amount of heat required to raise 1 pound of water from 63°F to 64°F.
(5) some units
1 joule = 0.2389 cal = 9.481 × 10-4BTU, 1 kcal = 1000 cal
(6) Heat transfer method
Conduction: Refers to the manner in which heat is transmitted by diffusion in a solid or in a liquid at rest.
Convection: Convection is the transfer of heat through the motion of a liquid or gas. Can be divided into free convection and forced convection. Free convection is the movement of fluids to transfer heat due to the existence of temperature gradients between them. Forced convection refers to the transfer of heat by moving a fluid through the outside world.
Radiation: Refers to the transfer of heat through the emission of electromagnetic waves.
3. Classification of temperature sensitive sensors
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Contact temperature sensors include: thermal expansion temperature sensor, thermoelectric potential temperature sensor, PN junction temperature sensor, integrated temperature sensor, etc.
Advantages: Mature technology, many types of sensors, large choice,
simple measurement system, high measurement accuracy
Disadvantages: The measurement temperature is not very high, which has an impact on the measured temperature field. -
Non-contact temperature sensors include: optical high temperature sensors, thermal radiation temperature
sensors, etc.
Advantages: The upper limit of the measurement temperature is not limited by the heat resistance of the temperature sensing element, so
there is no limit to the maximum temperature measurement in principle. When measuring temperature, it does not need to conduct
heat conduction exchange with the measured object, so it will not affect the temperature field of the measured object, and the measurement is
fast; it can measure the temperature of moving objects.
Disadvantages: The measurement error is large.
Summarize
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