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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: Thermocouples; Thermistors; Resistance temperature detector (RTD) Pyrometer; Langmuir probes (for electron temperature of a plasma) Infrared ...
A standard RTD sheath is 3.175 to 6.35 mm (0.1250 to 0.2500 in) in diameter; sheath diameters for thermocouples can be less than 1.6 mm (0.063 in). Accuracy and stability requirements If a tolerance of 2 °C is acceptable and the highest level of repeatability is not required, a thermocouple will serve.
A thermistor is a semiconductor type of resistor whose resistance is strongly dependent on temperature, more so than in standard resistors. The word thermistor is a portmanteau of thermal and resistor. Thermistors are categorized based on their conduction models.
A thermocouple probe. Temperature probes are used to make contact measurements of surface temperatures. They employ a temperature sensor such as a thermistor, thermocouple, or RTD, to produce a voltage that varies with temperature. In the case of thermistor and RTD probes, the sensor must be electrically stimulated to produce a voltage, whereas ...
Electronic thermostats, instead, use a thermistor or other semiconductor sensor, processing temperature change as electronic signals, to control the heating or cooling equipment. Conventional thermostats are example of " bang-bang controllers " as the controlled system either operates at full capacity once the setpoint is reached, or keeps ...
A thermocouple, also known as a "thermoelectrical thermometer", is an electrical device consisting of two dissimilar electrical conductors forming an electrical junction.A thermocouple produces a temperature-dependent voltage as a result of the Seebeck effect, and this voltage can be interpreted to measure temperature.
The thermoelectric effect is the direct conversion of temperature differences to electric voltage and vice versa via a thermocouple. [1] A thermoelectric device creates a voltage when there is a different temperature on each side. Conversely, when a voltage is applied to it, heat is transferred from one side to the other, creating a temperature ...
In practice the absolute Seebeck coefficient is difficult to measure directly, since the voltage output of a thermoelectric circuit, as measured by a voltmeter, only depends on differences of Seebeck coefficients. This is because electrodes attached to a voltmeter must be placed onto the material in order to measure the thermoelectric voltage.