German DISKOGRUPPEN sensors, DISKOGRUPPEN models, DISKOGRUPPEN prices

DISKOGRUPPEN sensors are sensors that can sense temperature and convert it into usable output signals. Temperature sensors are the core component of temperature measuring instruments and come in a wide variety. They can be divided into two major categories based on the measurement method: contact and non-contact. Based on sensor materials and electronic component characteristics, they are classified into resistance thermometers and thermocouples.

DISKOGRUPPEN sensor classification

1) Contact type: The sensing part of a contact temperature sensor has good contact with the object being measured, and is also called a thermometer. The thermometer reaches thermal equilibrium through conduction or convection, so that the indication of the thermometer can directly represent the temperature of the object being measured. Generally, the measurement accuracy is higher. Within a certain temperature measurement range, the thermometer can also measure the temperature distribution inside the object. However, large measurement errors will occur for moving objects, small targets, or objects with very small heat capacity. Commonly used thermometers include bimetallic thermometers, glass liquid thermometers, pressure-type thermometers, resistance thermometers, thermistors, and thermocouples. They are widely used in industry, agriculture, commerce, and other sectors. People also often use these thermometers in daily life. With the wide application of cryogenic technology in national defense engineering, space technology, metallurgy, electronics, food, medicine, petrochemicals, and other sectors, as well as research into superconducting technology, cryogenic thermometers for measuring temperatures below 120K have been developed, such as cryogenic gas thermometers, vapor pressure thermometers, acoustic thermometers, paramagnetic salt thermometers, quantum thermometers, cryogenic resistance thermometers, and cryogenic thermocouples. Cryogenic thermometers require sensing elements that are small in size, high in accuracy, and good in reproducibility and stability. A carburized glass resistance thermometer, made by sintering porous high-silica oxygen glass with carbon infiltration, is a type of sensing element for cryogenic thermometers and can be used to measure temperatures in the range of 1.6 to 300K. 2) Non-contact type: Its sensitive element does not come into contact with the object being measured, and it is also called a non-contact temperature measuring instrument. This type of instrument can be used to measure the surface temperature of moving objects, small targets, objects with small heat capacity, or objects with rapid (transient) temperature changes, and can also be used to measure the temperature distribution of a temperature field. The most commonly used non-contact temperature measuring instruments are based on the basic laws of blackbody radiation and are called radiation thermometry instruments. Radiation thermometry methods include the brightness method (see optical pyrometer), the radiation method (see radiation pyrometer), and the colorimetric method (see colorimetric thermometer). Various radiation thermometry methods can only measure the corresponding brightness temperature, radiation temperature, or colorimetric temperature. Only the temperature measured for a blackbody (an object that absorbs all radiation and does not reflect light) is the true temperature. If you want to determine the true temperature of an object, you must correct for the emissivity of the material surface. The emissivity of a material surface depends not only on temperature and wavelength, but also on surface condition, coating, and microstructure, making it difficult to measure precisely. In automated production, radiation thermometry is often used to measure or control the surface temperature of certain objects, such as the rolling temperature of steel strips in metallurgy, roll temperature, forging temperature, and the temperature of various molten metals in smelting furnaces or crucibles. In these specific cases, measuring the emissivity of the object's surface is quite difficult. For automatic measurement and control of solid surface temperature, an additional mirror can be used to form a blackbody cavity together with the measured surface. The influence of additional radiation can increase the effective radiation and effective emissivity of the measured surface. By using the effective emissivity to appropriately correct the measured temperature via the instrument, the true temperature of the measured surface can ultimately be obtained. The most typical additional mirror is a hemispherical mirror. Diffuse radiation energy from the measured surface near the center of the sphere is reflected back to the surface by the hemispherical mirror, forming additional radiation, thereby increasing the effective emissivity. In the formula, ε is the emissivity of the material surface, and ρ is the reflectivity of the mirror. As for the radiation measurement of the true temperature of gaseous and liquid media, a method of inserting a heat-resistant material tube to a certain depth to form a blackbody cavity can be used. The effective emissivity of the cylindrical cavity after reaching thermal equilibrium with the medium is calculated. In automatic measurement and control, this value can be used to correct the measured temperature at the bottom of the cavity (i.e., the medium temperature) to obtain the true temperature of the medium.

DISKOGRUPPEN sensor usage precautions

1) Errors introduced by improper installation: For example, the installation position and insertion depth of the thermocouple cannot reflect the true temperature of the furnace chamber. In other words, the thermocouple should not be installed too close to the door or heating elements, and the insertion depth should be at least 8 to 10 times the diameter of the protection tube; if the gap between the thermocouple protection tube and the wall is not filled with insulating material, heat leakage from the furnace or intrusion of cold air may occur. Therefore, the gap between the thermocouple protection tube and the furnace wall hole should be blocked with insulating materials such as refractory mud or asbestos rope to prevent convection of hot and cold air from affecting the accuracy of temperature measurement; if the cold junction of the thermocouple is too close to the furnace body, the temperature may exceed 100℃; the installation of the thermocouple should avoid strong magnetic and electric fields as much as possible, so the thermocouple and power cables should not be installed in the same conduit to avoid introducing interference and causing errors; the thermocouple should not be installed in areas where the measured medium has little flow. When using a thermocouple to measure the temperature of gas in a pipe, the thermocouple must be installed against the flow direction and have full contact with the gas. 2) Errors introduced by deteriorated insulation: If the thermocouple is insulated, excessive dirt or salt slag on the protection tube and pull plate can cause poor insulation between the thermocouple poles and the furnace wall, which is more severe at high temperatures. This not only causes loss of thermoelectric potential but also introduces interference, and the resulting error can sometimes reach hundreds of degrees. 3) Errors introduced by thermal inertia: Due to the thermal inertia of the thermocouple, the instrument's indication lags behind changes in the measured temperature, an effect that is particularly prominent during rapid measurements. Therefore, thermocouples with thinner thermoelectrodes and smaller protection tube diameters should be used as much as possible. If the temperature measurement environment permits, the protection tube can even be removed. Due to measurement lag, the amplitude of temperature fluctuations detected by the thermocouple is smaller than the amplitude of furnace temperature fluctuations. The greater the measurement lag, the smaller the amplitude of the thermocouple fluctuation, and the greater the difference from the actual furnace temperature. When using a thermocouple with a large time constant for temperature measurement or control, although the temperature displayed by the instrument fluctuates very little, the actual furnace temperature fluctuation may be large. To measure temperature accurately, a thermocouple with a small time constant should be selected. The time constant is inversely proportional to the heat transfer coefficient and directly proportional to the diameter of the thermocouple's hot junction, the density of the material, and the specific heat. To reduce the time constant, in addition to increasing the heat transfer coefficient, the most effective method is to minimize the size of the hot junction. In use, materials with good thermal conductivity, thin-walled tubes, and small inner diameter protection sleeves are typically used. In more precise temperature measurements, bare-wire thermocouples without protection sleeves are used, but thermocouples are prone to damage and should be calibrated and replaced in a timely manner. 4) Thermal resistance error: At high temperatures, if there is a layer of coal ash or dust on the protection tube, thermal resistance increases, hindering heat conduction, and the temperature indication will be lower than the true value of the measured temperature. Therefore, the exterior of the thermocouple protection tube should be kept clean to reduce errors.

DISKOGRUPPEN sensor industry applications

Temperature sensors are the earliest developed and most widely used type of sensor. The market share of temperature sensors greatly exceeds that of other sensors. Since the beginning of the 17 century, people have begun to use temperature for measurement. Supported by semiconductor technology, semiconductor thermocouple sensors, PN junction temperature sensors, and integrated temperature sensors have been successively developed in this century. Two conductors of different materials, if connected together at a point, will exhibit a potential difference at their unheated parts when this connection point is heated. The value of this potential difference is related to the temperature of the measurement point at the unheated part and to the material of these two conductors. This phenomenon can occur over a wide temperature range. If this potential difference is measured precisely, and the ambient temperature of the unheated part is measured, the temperature of the heating point can be accurately determined. Because it requires two conductors of different materials, it is called a "thermocouple". Thermocouples made of different materials are used in different temperature ranges, and their sensitivities vary. Thermocouple sensors have their own advantages and disadvantages; their sensitivity is relatively low, they are easily affected by environmental interference signals, and they are also susceptible to the temperature drift of the preamplifier, making them unsuitable for measuring minute temperature changes. Since the sensitivity of thermocouple temperature sensors is unrelated to the thickness of the material.

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