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使用误差很小的普通热电偶高温计,不一定能准确测得某些特殊对象的温度。本文以挤压制造用的测温热电偶为例,说明在用接触法测量特殊对象的温度时,热电偶的测量端结构及测量方法等应满足的一些特殊要求。挤压铸造时,铝合金熔液的温度对挤压铸件质量影响极大。特别是由于挤铸机内的铝液很浅、温度下降很快,故需进行液体浅层测温、阶变测温和迅变测温这样具有三个特点的特殊测温。用普通结构的热电偶(如WREU-110型)根本无法读出被测温度。在此,我们结合实际,分析三种特殊情况下造成测温误差的原因并说明减小误差的方法。 1.液体浅层测温挤铸机内铝液很浅,只能允许热电偶垂直插入50mm。测温时,沿热电偶保护管、热电极的导热损失,使测量端温度t_c低于被测介质温度t_e而造成导热误差为:
The use of ordinary thermocouple pyrometers with small errors may not accurately measure the temperature of some special objects. In this paper, the temperature measurement thermocouple used for extrusion manufacturing as an example to illustrate the use of contact measurement of the temperature of special objects, thermocouple measurement end structure and measurement methods should meet some of the special requirements. Squeeze casting, the temperature of aluminum alloy extrusion die casting quality greatly affected. Especially due to the casting machine is very shallow liquid aluminum, the temperature dropped quickly, it is necessary to liquid shallow temperature, temperature and temperature change of the rapid change of temperature with three special temperature measurement. With ordinary structure of the thermocouple (such as WREU-110 type) simply can not read out the measured temperature. Here, we combine the actual analysis of the causes of the temperature error caused by three special cases and illustrate the method to reduce the error. 1. Liquid shallow temperature casting machine within the aluminum liquid is very shallow, only to allow vertical thermocouple 50mm. Temperature measurement, along the thermocouple protection tube, the thermal conductivity of the heat loss, so that the measured end temperature t_c lower than the measured medium temperature t_e caused thermal conductivity error: