Thermal inertia causes thermocouple measurement errors

Because the thermal inertia of thermocouple on measurement error resulted from the situation is more complex, and the scene is also associated with many factors, so we in the selection of products, need to fully consider the various aspects of different factors, because the thermal inertia in the thermocouple will lead to the indicated value of the instrument, less than the measured values of temperature changes, especially in the fast measurement, this kind of situation will be more obvious and prominent, can use hot electrode is fine as far as possible, and the thermocouple protection tube diameter smaller, if the temperature of the environmental permits, can remove protection tube directly. Because there are hysteresis, measured using thermocouples to test the temperature, the temperature on the volatility than temperature fluctuations in much smaller, so the measurement of the lag, the thermocouple on the width of fluctuation in the smaller, and practical in the greater the differences in temperature will also. If using a thermocouple for temperature control of the time constant is larger or the temperature, while the relatively small fluctuations of temperature of the instrument, but in fact furnace temperature on the volatility is larger, the temperature is measured in order to more accurate, is that you can choose in relatively small thermocouple time constant, because of the time constant and the coefficient of heat transfer between the positive and negative than with thermocouples on the hot side is direct ratio between material, diameter and density, so want to reduce the time constant, not only will increase the coefficient of heat transfer, also can effectively reduce the size of the on the hot side, but in the use process, more commonly used is the heat conduction performance is good material, mainly the wall is thin, and the protection of the inside diameter smaller casing, if it is done in a more precise temperature measurement, can be used not to protect casing naked wire thermocouple, thermocouple is prone to damage, but this situation need to periodically for correction and replacement.