High temperature measurement

Thermocouples are mainly used for contact-type high temperature measurement.
For thermocouple measurements, a compensating lead wire is used to connect the instrument to the thermocouple. A thermal gradient applied to this compensating lead may cause measurement error. A thermocouple can measure correctly by sufficiently acclimating the temperature to the object to be measured and generating a thermal gradient between the measured temperature and room temperature on the thermocouple itself. However, base-metal thermocouples, in particular, must be replaced regularly because their service heat history affects the measurements. As for the precious metal thermocouple, if the thermocouple wire becomes contaminated, the measured value will be affected.
Also, when inserting the thermometer into a furnace, etc., the outer diameter of the thermometer must be considered to avoid measurement errors due to heat flow. When inserting a thermometer with a large outside diameter into a furnace, etc., it is necessary to take measures such as inserting a sufficient length or take care because the amount of heat of the object to be measured travels through the thermometer and escapes.
When installing the thermometer on the object to be measured, the measurement accuracy is enhanced by improving the contact. Even in temperature calibration, variations in measurement can be reduced by improving the temperature distribution and temperature stability in the furnace during calibration.

A radiation thermometer is used for non-contact high-temperature measurement.
When measuring with a radiation thermometer, it is important to grasp the emissivity of the material of the object to be measured and to select an appropriate measuring method. When measuring, the target part of the radiation thermometer must be completely within the measuring object. A lack of field of view in which the target does not completely fit in the object to be measured may cause measurement errors.