DANFOSS temperature sensor

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The detection part of the DANFOSS Danfoss temperature sensor in the United States has good contact with the measured object

A temperature transducer refers to a sensor that can sense temperature and convert it into a usable output signal.DANFOSS temperature sensorIt is the core part of temperature measuring instruments, with a wide variety of varieties. According to the measurement method, it can be divided into two categories: contact and non-contact. According to the characteristics of sensor materials and electronic components, it can be divided into two categories: thermistor and thermocouple.

contact-type

contact-typeDANFOSS temperature sensorThe detection part has good contact with the tested object, also known as a thermometer.

A thermometer achieves thermal equilibrium through conduction or convection, allowing its reading to directly represent the temperature of the object being measured. Generally, the measurement accuracy is relatively high. Within a certain temperature range, a thermometer can also measure the temperature distribution inside an object. However, for moving objects, small targets, or objects with low thermal capacity, significant measurement errors may occur. Commonly used thermometers include bimetallic thermometers, glass liquid thermometers, pressure thermometers, resistance thermometers, thermistors, and thermocouples. They are widely used in industries, agriculture, commerce, and other sectors. People often use these thermometers in their daily lives. With the widespread application of low-temperature technology in sectors such as space technology, metallurgy, electronics, food, medicine, and petrochemicals, as well as research on superconducting technology, low-temperature thermometers for measuring temperatures below 120K have been developed, such as low-temperature gas thermometers, vapor pressure thermometers, acoustic thermometers, paramagnetic salt thermometers, quantum thermometers, low-temperature thermistors, and low-temperature thermocouples. Low temperature thermometers require temperature sensing elements with small size, high accuracy, good reproducibility, and stability. The carburizing glass thermistor made by carburizing and sintering porous high silica glass is a temperature sensing element of low-temperature thermometers, which can be used to measure temperatures in the range of 1.6-300K.

non-contact

Its sensitive components are not in contact with the measured object, also known as non-contact temperature measuring instruments. This instrument can be used to measure the surface temperature of moving objects, small targets, and objects with small heat capacity or rapid temperature changes (transients), as well as to measure the temperature distribution of the temperature field.

The non-contact thermometer based on the fundamental law of blackbody radiation is called a radiation thermometer. Radiation temperature measurement methods include brightness method (see optical pyrometer), radiation method (see radiation pyrometer), and colorimetric method (see colorimetric thermometer). Various radiation temperature measurement methods can only measure the corresponding photometric temperature, radiation temperature, or colorimetric temperature. Only the temperature measured for a blackbody (an object that absorbs all radiation but does not reflect light) is the true temperature. To determine the true temperature of an object, it is necessary to correct the emissivity of the material surface. The surface emissivity of materials depends not only on temperature and wavelength, but also on surface state, coating, and microstructure, making it difficult to measure accurately. In automated production, it is often necessary to use radiation thermometry to measure or control the surface temperature of certain objects, such as steel strip rolling temperature, roll temperature, forging temperature, and the temperature of various molten metals in smelting furnaces or crucibles in metallurgy. In these specific situations, measuring the emissivity of an object's surface is quite difficult. For automatic measurement and control of solid surface temperature, additional mirrors can be used to form a blackbody cavity together with the measured surface. The effect of additional radiation can increase the effective radiation and effective emission coefficient of the measured surface. By using the effective emission coefficient to adjust the measured temperature through instruments, the true temperature of the measured surface can be obtained. The most typical additional reflector is a hemispherical reflector. The diffuse radiation on the surface near the center of the sphere can be reflected back to the surface by the hemispherical mirror, forming additional radiation, thereby increasing the effective emission coefficient. In the formula, ε is the surface emissivity of the material, and ρ is the reflectivity of the reflector. As for the radiation measurement of the true temperature of gas and liquid media, the method of inserting a heat-resistant material tube to a certain depth to form a blackbody cavity can be used. Calculate the effective emission coefficient of the cylindrical cavity after reaching thermal equilibrium with the medium. In automatic measurement and control, this value can be used to correct the measured chamber bottom temperature (i.e. medium temperature) and obtain the true temperature of the medium.

Advantages of non-contact temperature measurement: The upper limit of measurement is not limited by the temperature resistance of the sensing element, so there is no limit on the highest measurable temperature in principle. For high temperatures above 1800 ℃, non-contact temperature measurement methods are mainly used. With the development of infrared technology, radiation temperature measurement has gradually expanded from visible light to infrared, and has been adopted below 700 ℃ until room temperature, with high resolution.

Sensors designed based on the principle of metal expansion

Metals will undergo a corresponding extension after changes in ambient temperature, so sensors can convert this reaction into signals in different ways.

Bimetallic sensor

A bimetallic strip is composed of two metals with different coefficients of expansion attached together. As the temperature changes, material A expands more than the other metal, causing the metal strip to bend. The curvature of curvature can be converted into an output signal.

Bimetallic rod and metal tube sensor

As the temperature increases, the length of the metal tube (material A) increases, while the length of the non expanding steel rod (metal B) does not increase. Therefore, due to the change in position, the linear expansion of the metal tube can be transmitted. Conversely, this linear expansion can be converted into an output signal.

Sensors for designing deformation curves of liquids and gases

When the temperature changes, both liquids and gases will experience corresponding changes in volume.

Multiple types of structures can convert this expansion change into a change in position, resulting in a change in position output (potentiometer, induction deviation, baffle, etc.).

A thermocouple consists of two metal wires made of different materials, welded together at the ends. By measuring the ambient temperature of the unheated area, the temperature of the heating point can be accurately determined. Because it requires two different materials of conductors, it is called a thermocouple. Thermocouples made of different materials are used in different temperature ranges, and their sensitivity also varies. The sensitivity of a thermocouple refers to the change in output potential difference when the heating point temperature changes by 1 ℃. For most metal supported thermocouples, this value is approximately between 5-40 microvolts/℃

Due to the sensitivity of the thermocouple DANFOSS temperature sensor being independent of the thickness of the material, even very fine materials can be used to make DANFOSS temperature sensors. Also, due to the excellent ductility of the metal materials used to make thermocouples, this subtle temperature measuring element has a response speed that can measure rapidly changing processes.