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答: 采用热电偶测温的特点是:只要热接点和冷接点的温度确定后,便能得到相应的电动势,而与热电偶中间点的温度无关。但当把热电偶热接点贴紧,甚至焊在被测表面上时,热接点的温度也不一定与被测点的温度完全一致。下面分别就不同情况分析造成这种误差的原因。 1.当测量具有保温层的金属壁面温度时(即要求沿被测表面垂直方向的热流尽可能小,例如通过测量管壁温度确定管内蒸汽温度等),
A: The use of thermocouple temperature measurement is characterized by: as long as the hot junction and cold junction temperature is determined, you can get the corresponding electromotive force, and the temperature of the midpoint of the thermocouple has nothing to do. However, when the thermocouple hot contact tightly, or even welded on the surface to be measured, the temperature of the hot junction is not necessarily the temperature of the measured point exactly the same. The following analysis of the different circumstances of the reasons for this error. 1. When measuring the temperature of a metal wall with a thermal insulation (ie requiring that the heat flow in the vertical direction of the measured surface should be as small as possible, eg by measuring the wall temperature to determine the temperature of the steam in the tube, etc.)