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These include helium vapor pressure thermometers, helium gas thermometers, standard platinum resistance thermometers (known as SPRTs) and monochromatic radiation thermometers. Although the Kelvin and Celsius temperature scales were (until 2019) defined using the triple point of water ( 273.16 K or 0.01 °C ), it is impractical to use this ...
This definition also precisely related the Celsius scale to the Kelvin scale, which defines the SI base unit of thermodynamic temperature with symbol K. Absolute zero, the lowest temperature possible, is defined as being exactly 0 K and −273.15 °C. Until 19 May 2019, the temperature of the triple point of water was defined as exactly 273.16 ...
Such thermometers are usually calibrated so that one can read the temperature simply by observing the level of the fluid in the thermometer. Another type of thermometer that is not really used much in practice, but is important from a theoretical standpoint, is the gas thermometer. Other important devices for measuring temperature include:
The Callendar–Van Dusen equation is an equation that describes the relationship between resistance (R) and temperature (T) of platinum resistance thermometers (RTD). As commonly used for commercial applications of RTD thermometers, the relationship between resistance and temperature is given by the following equations.
T g = Globe thermometer temperature (measured with a globe thermometer, also known as a black globe thermometer) T d = Dry-bulb temperature (actual air temperature) Temperatures may be in either Celsius or Fahrenheit; Indoors the following formula is used: = +
The kelvin (K) is now fixed in terms of the Boltzmann constant (k B) and the joule. The joule is not shown because it is a derived unit defined by the metre (m), second (s), and kilogram (kg). Those SI base units are themselves defined by the universal constants of the speed of light ( c ), the caesium-133 hyperfine transition frequency ( Δ ν ...
A recording thermometer is a type of thermometer that records temperature changes over a period of time. A digital recording thermometer is often called a temperature data logger . Analog temperature recorders
The IPCC Second Assessment Report (SAR) of 1996 featured Figure 3.20 showing the Bradley & Jones 1993 decadal summer temperature reconstruction for the northern hemisphere, overlaid with a 50-year smoothed curve and with a separate curve plotting instrumental thermometer data from the 1850s onwards. It stated that in this record, warming since ...