Precautions for operating thermocouple protection tubes

Improper installation and use of thermocouple protection tubes can increase measurement errors and reduce their service life. Therefore, it is crucial to install and use them correctly and appropriately, based on the temperature measurement range and working environment. Below are some points to note regarding the operation of thermocouple protection tubes:

When using thermocouple protection tubes, a suitable installation location should be chosen. Since the hot junction of the thermocouple protection tube can only measure the temperature of a small surrounding area, it should be installed in a furnace chamber with a relatively uniform temperature to accurately represent the actual temperature of the workpiece. It should not be installed on the furnace door, too close to, or too close to a heat source. The installation location should avoid strong magnetic and electric fields as much as possible to minimize measurement errors caused by external interference. For example, in an electrode salt bath furnace, it should not be placed too close to the electrodes. Furthermore, the insertion depth into the furnace chamber should be moderate. Too shallow an insertion depth will not reflect the true temperature of the furnace chamber; however, too deep an insertion depth will easily damage the thermocouple during component handling. The insertion depth is generally not less than 8 to 10 times the outer diameter of the thermocouple protection tube. Additionally, please note that the junction box of the thermocouple protection tube should not be placed near the furnace wall to avoid excessively high cold junction temperatures, which could affect the measurement accuracy of the instrument. Generally, a distance of about 200mm from the furnace wall is recommended. To prevent deformation due to high temperatures, it should be installed as vertically as possible.

If horizontal installation is necessary, the insertion depth into the furnace should not be too great, generally below 500mm, and the furnace body should be supported by a bracket. After a period of use, the thermocouple protection tube should be rotated 180° for continued use. When measuring temperature in a salt bath furnace, right-angle thermocouples are often used to prevent the thermocouple junction box from overheating. Besides these points, please also ensure that the vent hole where the thermocouple protection tube passes through the furnace wall is sealed to prevent air convection from affecting measurement accuracy and to provide insulation. The outlet hole of the junction box should also be sealed, with the opening facing downwards to prevent dirt from falling in. When measuring low temperatures, thermocouples with or without protection tubes can be used. It is also recommended that you regularly check the thermocouple parts for damage. If any damage is found, it should be stopped from use and repaired or replaced. In short, it has a wide measurement range. Common thermocouple protection tubes can continuously measure temperatures from -50℃ to 1600℃, while some special thermocouples can measure temperatures as low as -269℃ (such as gold-iron-nickel-chromium) and as high as 2800℃ (such as tungsten-rhenium). It has a simple structure and is easy to use.

The above article discusses the operation of thermocouple protection tubes. If you are still unfamiliar with them, please read on. That's all for this topic; we hope it has been helpful. As our factory's flagship product, we appreciate the strong support of both new and old customers. While ensuring the reliability of our product quality, we also offer competitive prices to our customers. If you have any technical questions about our products, please feel free to contact us at any time.