Temperature Sensor A temperature sensor is a sensor that can sense the temperature and convert it into an available output signal. Temperature sensor is the core of temperature measurement instruments, a wide variety. According to the measurement method can be divided into contact and non-contact two categories, according to the sensor material and electronic components are divided into two types of thermal resistance and thermocouple
Contact the temperature sensor detection part and the measured object has a good contact, also known as thermometer.
The thermometer achieves thermal equilibrium by conduction or convection, so that the thermometer's indication can directly represent the temperature of the object to be measured.
Temperature Sensor General measurement accuracy is higher. In a certain temperature range, the thermometer can also measure the temperature distribution within the object. But for the movement of small objects or small heat capacity will produce a large measurement error, commonly used thermometer bimetallic thermometer, glass liquid thermometer, pressure thermometer, resistance thermometer, thermistor and thermocouple and so on. They are widely used in industrial, agricultural, commercial and other sectors. People often use these thermometers in their daily lives. With the low temperature technology in the defense engineering, space technology, metallurgy, electronics, food, medicine and petrochemical and other departments of the extensive application and superconducting technology research, measuring temperature below 120K low temperature thermometer has been developed, such as low temperature gas thermometer, Pressure thermometer, acoustic thermometer, paramagnetic thermometer, quantum thermometer, low temperature thermal resistance and low temperature thermocouple. Low temperature thermometer requires temperature sensor components small size, high accuracy, reproducibility and stability. The use of porous high silica glass carburizing sintered carburized glass thermal resistance is a low temperature thermometer temperature sensor can be used to measure the temperature range of 1.6 ~ 300K.
Its sensitive components and the measured object is not in contact with each other, also known as non-contact thermometer. This meter can be used to measure the surface temperature of moving objects, small targets and heat capacity or temperature changes rapidly (transient) objects, and can also be used to measure the temperature distribution of the temperature field.
The most commonly used non-contact thermometer based on the basic law of blackbody radiation, known as radiation thermometer.
Temperature Sensor Radiation temperature method includes brightness method (see optical pyrometer), radiation method (see radiation pyrometer) and colorimetric method (see color temperature thermometer). All kinds of radiation temperature measurement method can only measure the corresponding luminous temperature, radiation temperature or color temperature. Only the black body (absorb all the radiation does not reflect the light of the object) measured temperature is the real temperature. To determine the true temperature of the object, it is necessary to modify the surface emissivity of the material. The surface emissivity of the material depends not only on the temperature and wavelength, but also on the surface state, coating and microstructure, etc., it is difficult to accurately measure. In the automated production often need to use radiation temperature measurement method to measure or control the surface temperature of some objects, such as metallurgical steel rolling temperature, roll temperature, forging temperature and a variety of molten metal in the furnace or crucible temperature The In these specific cases, the measurement of the surface emissivity of the object is quite difficult. For automatic measurement and control of the solid surface temperature, additional mirrors can be used to form the blackbody cavity together with the surface to be measured. The effect of additional radiation can increase the effective radiation and effective emission coefficient of the measured surface. Using the effective emission coefficient through the instrument on the measured temperature of the corresponding correction, and ultimately get the measured surface of the real temperature. The most typical additional reflector is a hemispherical reflector. The diffuse radiation near the center of the sphere can be reflected back to the surface by the hemispherical mirror to form additional radiation, thereby increasing the effective emission coefficient where ε is the surface emissivity of the material and ρ is the reflectivity of the mirror.
As for the radiation measurement of the true temperature of the gas and liquid medium, a method of inserting a heat-resistant material tube to a certain depth to form a blackbody cavity can be used. The effective emission coefficient of the cylinder cavity after the heat balance with the medium is calculated. In the automatic measurement and control can use this value on the measured cavity bottom temperature (ie, the medium temperature) to be corrected to get the real temperature of the medium.
Temperature Sensor Non-contact temperature measurement Advantages: The upper limit of the measurement is not limited by the temperature tolerance of the temperature sensing element, so there is no limit to the maximum measurable temperature. For 1800 ℃ above the high temperature, the main use of non-contact temperature measurement method. With the development of infrared technology, radiation temperature gradually from the visible light to the infrared expansion, 700 ℃ below the room temperature have been used, and the resolution is high.