When calibrating thermocouples, thermocouple calibration furnace and portable dry block furnace are generally used. According to different heating element materials, thermocouple calibration furnaces used in laboratories can generally be divided into nickel-chromium wire calibration furnaces and iron-chromium-aluminum wire calibration furnace , Platinum rhodium wire calibration furnace, molybdenum wire calibration furnace, silicon carbide calibration furnace, tantalum tube furnace and tungsten tube furnace.

Technical Requirements for Thermocouple Calibration Furnace：

1. It needs to meet the temperature of the test point of the thermocouple being tested, and has a certain service life. For example, the platinum rhodium 10-platinum thermocouple regulation requires that the calibration point temperature is 1084.62°C, so the long-term use temperature of the calibration furnace is not lower than 1100°C; the calibration platinum rhodium 30-platinum rhodium 6 thermocouple regulation requires the calibration point temperature to be 1500°C, Therefore, the long-term use temperature of the calibration furnace is required to be not lower than 1500°C; the calibration point temperature of the K-type thermocouple is 1200°C, so the long-term use temperature of the calibration furnace is required to be 1200°C.

2. In order to reduce the heat conduction error and ensure that the thermocouple has a certain insertion depth during the verification, the material, diameter and length of the furnace will be required. For example: the length of the verification furnace requires about 600mm, and the interior is composed of three layers of alumina tube: winding wire The size of the tube is Φ40mm*50mm*600mm; the size of the outer tube is Φ70mm*80mm*600mm; the size of the inner tube of the verified precious metal thermocouple is about Φ15mm*20mm*600mm; the size of the inner tube of the verified cheap metal thermocouple can be determined according to the specific situation. When verifying short thermocouples of 200-700mm, the length of the verification furnace is about 300mm. Furnace material, diameter and length can be customized according to needs.

3. In order to ensure the quality of the calibration, the temperature distribution of the temperature field of the calibration furnace along the axial direction should be high in the middle and low at both ends. The highest temperature point deviates from the geometric center position, and the calibration furnace for platinum-rhodium series thermocouples shall not exceed 20mm, and there is a uniform temperature field with a temperature gradient of 0.5°C/10mm within 200mm of the highest point; For 200-700mm short thermocouple calibration furnace and base metal thermocouple calibration furnace, the temperature point deviation from the geometric center shall not exceed 10mm.

4. The atmosphere in the calibration furnace should meet the requirements of the thermocouple to be tested and the components of the calibration furnace.

5. In order to improve the verification efficiency and facilitate operation, the thermocouple verification furnace is required to heat up quickly and have good heat preservation performance.