溫度傳感器是指能感受溫度并轉換成可用輸出信號的傳感器。溫度傳感器是溫度測量儀表的核心部分，品種繁多。按測量方式可分為接觸式和非接觸式兩大類，按照傳感器材料及電子元件特性分為熱電阻和熱電偶兩類。
溫度傳感器在安裝和使用時，應當注意以下事項：
1、安裝不當引入的誤差
如熱電偶安裝的位置及插入深度不能反映爐膛的真實溫度等，換句話說，熱電偶不應裝在太靠近門和加熱的地方，插入的深度至少應為保護管直徑的8～10倍;熱電偶的保護套管與壁間的間隔未填絕熱物質致使爐內熱溢出或冷空氣侵入，因此熱電偶保護管和爐壁孔之間的空隙應用耐火泥或石棉繩等絕熱物質堵塞以免冷熱空氣對流而影響測溫的準確性;熱電偶冷端太靠近爐體使溫度超過100℃;熱電偶的安裝應盡可能避開強磁場和強電場，所以不應把熱電偶和動力電纜線裝在同一根導管內以免引入干擾造成誤差；熱電偶不能安裝在被測介質很少流動的區域內，當用熱電偶測量管內氣體溫度時，必須使熱電偶逆著流速方向安裝，而且充分與氣體接觸。
2、絕緣變差而引入的誤差
如熱電偶絕緣了，保護管和拉線板污垢或鹽渣過多致使熱電偶極間與爐壁間絕緣不良，在高溫下更為嚴重，這不僅會引起熱電勢的損耗而且還會引入干擾，由此引起的誤差有時可達上百度。
3、熱惰性引入的誤差
由于熱電偶的熱惰性使儀表的指示值落后于被測溫度的變化，在進行快速測量時這種影響尤為突出。所以應盡可能采用熱電極較細、保護管直徑較小的熱電偶。測溫環境許可時，甚至可將保護管取去。由于存在測量滯后，用熱電偶檢測出的溫度波動的振幅較爐溫波動的振幅小。測量滯后越大，熱電偶波動的振幅就越小，與實際爐溫的差別也就越大。當用時間常數大的熱電偶測溫或控溫時，儀表顯示的溫度雖然波動很小，但實際爐溫的波動可能很大。為了準確的測量溫度，應當選擇時間常數小的熱電偶。時間常數與傳熱系數成反比，與熱電偶熱端的直徑、材料的密度及比熱成正比，如要減小時間常數，除增加傳熱系數以外，最有效的辦法是盡量減小熱端的尺寸。使用中，通常采用導熱性能好的材料，管壁薄、內徑小的保護套管。在較精密的溫度測量中，使用無保護套管的裸絲熱電偶，但熱電偶容易損壞，應及時校正及更換。
溫度傳感器在安裝和使用時應注意哪些問題？
4、熱阻誤差
高溫時，如保護管上有一層煤灰，塵埃附在上面，則熱阻增加，阻礙熱的傳導，這時溫度示值比被測溫度的真值低。因此，應保持熱電偶保護管外部的清潔，以減小誤差。
當然，昆山丹瑞傳感測控在溫度傳感器上的行業應用案例較為豐富，在產品和行業中有著多年的實際操作經驗，如果你對你目前遇到的傳感器問題無法解決，請咨詢右側在線客服或撥打客服熱線，昆山丹瑞將免費提供解答。
A temperature sensor is a sensor that can sense temperature and convert it into usable output signal. Temperature sensor is the core part of the temperature measuring instrument. According to the characteristics of sensor materials and electronic components, it can be divided into two categories: contact type and non-contact type.
When installing and using temperature sensors, we should pay attention to the following matters:
1. Error caused by improper installation.
In other words, the thermocouple should not be installed too close to the door and the heating place, the insertion depth should be at least 8-10 times the diameter of the protective tube; the insulation between the protective sleeve and the wall of the thermocouple does not fill in the insulation material, resulting in heat overflow or cold air in the furnace. Therefore, the gap between the protective tube of thermocouple and the hole of furnace wall should be blocked by insulating material such as refractory mud or asbestos rope so as to avoid convection of cold and hot air affecting the accuracy of temperature measurement; the cold end of thermocouple is too close to the furnace body to make the temperature exceed 100 degrees Celsius; the installation of thermocouple should avoid the strong magnetic field and electric field as far as possible, so the thermocouple and the furnace should not be placed. The power cable is installed in the same duct to avoid interference, and the thermocouple can not be installed in the area where the medium under test is rarely flowing.
2. Error caused by insulation deterioration.
If the thermocouple is insulated, too much dirt or salt slag in the protective tube and the pull-wire board will lead to poor insulation between the thermocouple and the furnace wall, even more serious at high temperatures. This will not only cause the loss of thermoelectric power but also introduce interference, resulting in errors sometimes up to Baidu.
3. The error introduced by thermal inertia.
Because of the thermal inertia of the thermocouple, the indicator value of the instrument lags behind the change of the measured temperature, which is especially prominent in the rapid measurement. Therefore, the thermocouple with smaller diameter and smaller diameter should be used as far as possible. Protection can be taken even when the temperature is permitted. Because of the measurement lag, the amplitude of temperature fluctuation detected by thermocouple is smaller than that of furnace temperature fluctuation. The larger the measured lag, the smaller the amplitude of the thermocouple fluctuation, the greater the difference between the actual temperature and the actual furnace temperature. When the temperature is measured or controlled by a thermocouple with a large time constant, the temperature shown by the instrument fluctuates very little, but the actual furnace temperature may fluctuate greatly. In order to accurately measure the temperature, a thermocouple with small time constant should be chosen. The time constant is inversely proportional to the heat transfer coefficient, and is proportional to the diameter of the thermocouple hot end, the density of the material and the specific heat. If we want to reduce the time constant, the most effective way is to reduce the size of the thermocouple hot end as far as possible, in addition to increasing the heat transfer coefficient. Generally, the protective sleeve with good thermal conductivity, thin wall and small inner diameter is usually used. In more precise temperature measurement, bare-wire thermocouple without protective sleeve is used, but the thermocouple is easy to be damaged and should be corrected and replaced in time.
What problems should be noticed when installing and using temperature sensors?
4, thermal resistance error
At high temperatures, if there is a layer of coal ash on the protective pipe, dust attached to it, the thermal resistance increases, hindering the conduction of heat, at this time the temperature indication is lower than the true value of the temperature measured. Therefore, the external cleaning of the thermocouple protection tube should be kept to reduce the error.
Of course, Kunshan Than Shwe sensor monitoring and control in the temperature sensor industry more abundant applications, in the product and industry has many years of practical experience, if you are currently encountering sensor problems can not be solved, please consult the right online customer service or call the customer service hotline, Kunshan Than Shwe will provide free answers.
