Selecting the right thermocouple calibration furnace is a decision that can significantly impact the accuracy of temperature measurements in your operations. Here are some essential factors to keep in mind.
Temperature Range
The first and foremost consideration is the temperature range required for your thermocouple calibration. Different applications demand different temperature spans. For example, if you are calibrating thermocouples used in high - temperature industrial processes such as steel manufacturing or glass production, you'll need a furnace that can reach temperatures upwards of 1000 °C. Standards like AMS 2750 and Euramet CG - 8 even require calibration over the full temperature range in which the thermocouple will be used. So, ensure the furnace you choose has a wide enough temperature range to cover your specific needs.
Accuracy and Stability
A high - quality thermocouple calibration furnace should offer excellent accuracy and stability. Look for furnaces that can maintain a stable temperature with minimal fluctuations. Axial and radial temperature uniformity are crucial aspects. Some top - tier furnaces can achieve axial temperature uniformity of ± 0.2 °C over a 60 mm zone when using an isothermal block at 1200 °C, and radial (hole - to - hole) uniformity of ± 0.25 °C at the same temperature. Such precision ensures that the thermocouples being calibrated are exposed to a consistent temperature, leading to more reliable calibration results.
Configuration Flexibility
The ability to calibrate different types of thermocouples is another important factor. Some furnaces can be configured in multiple ways. For example, they may have the option to operate with or without an isothermal block. A tube furnace configuration (without an isothermal block) is suitable for base - metal thermocouples, often sheathed in materials like braided fiberglass or PTFE. On the other hand, an isothermal block configuration is better for metal - or ceramic - sheathed thermocouples with noble - metal thermo elements, as it improves heat transfer and temperature stability.
Immersion Depth
Industry standards like AMS2750 recommend calibrating thermocouples at their normal working depth of insertion. Consider the immersion depth of the furnace. A furnace with a sufficient immersion depth, such as 365 mm when using an isothermal block or 350 mm to the central point of the furnace without a block, is more likely to meet your calibration requirements, especially for longer thermocouples.
In summary, by carefully evaluating these aspects, you can make an informed decision and choose a thermocouple calibration furnace that best suits your calibration needs.
