Thermal resistor is low temperature zone in one of the most commonly used temperature detector.Thermal resistance temperature measurement is based on the metal conductor resistance value increases with the increase of the temperature of the properties for temperature measurement.Its main characteristic is high accuracy, stable performance.The platinum thermal resistance measurement accuracy is the highest, it is not only widely used in industrial temperature measurement, and is made into standard benchmark instrument.Heat resistance is mostly made of pure metal materials, the application at present most is platinum and copper, in addition, now have begun to use the materials such as nickel, manganese and rhodium manufacturing thermal resistance.Metal thermal resistance of the commonly used thermal material sort is more, the most commonly used is a platinum wire.Industrial measuring with metal thermal resistance materials in addition to the platinum wire, as well as copper, nickel, iron, iron, nickel, etc.
Armored thermal resistance
Armored thermal resistance is by thermal element (resistance), wire, insulation materials, stainless steel casing combination solid body, its diameter is generally from 2 -- 8 mm, minimum of phi mm.Compared with the normal thermal resistance, it has the following advantages:
1, small volume, no internal air gap and thermal inertia, small measuring hysteresis;
2, good mechanical properties and resistance to vibration and impact resistant;
3, can bend, easy to install;
4, long service life.
Temperature measurement principle
Thermal resistance temperature measurement principle and the temperature measurement principle of the thermocouple, heat resistance, which is based on the heating effect of the resistance temperature measurement, namely the resistance characteristics of the resistance varies with temperature.Therefore, as long as the measured feeling warm resistance of the resistance change, can measure the temperature.At present there are mainly metal thermal resistance and semiconductor thermistor two categories.
Metal thermal resistance of the resistance value and temperature can use the following general approximate relation said, namely
Rt = Rt0 [1 + alpha (t - t0)]
Type of Rt for temperature t resistance;Rt0 for temperature t0 (usually t0 = 0'C) corresponding to the resistance;Alpha for temperature coefficient.
The relationship between resistance and temperature of semiconductor thermistor is
Rt = AeB/t
Type of Rt for temperature t resistance;A and B depends on the structure of the semiconductor material constant.
In comparison, the thermistor temperature coefficient is bigger, room temperature resistance value higher (usually over thousands of Europe), but the poor compatibility, nonlinear, temperature measuring range, only 50 ~ 300'C or so, a large number of used in home appliances and automotive temperature detection and control.Metal thermal resistance is generally applicable to - 200 ~ 200'C temperature measurement range, is characterized by measuring accuracy, good stability, reliable performance, is widely application in process control.
Industry commonly used metal thermal resistance from the perspective of the change of resistance with temperature, most of the metal conductor has this property, but not all can be used for measuring temperature resistance, as the heat resistance of the metal material general requirements:As far as possible big and stable temperature coefficient, resistivity larger (reduce the size of the sensor under the same sensitivity), in the use of the temperature range has the stable chemical physical properties, good replication of material and resistance change with temperature have the function relationship between the (best linear relationship).
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