Types and structural forms of thermocouples

Thermocouples can be divided into ordinary type, armored type, high-performance solid type, and special type according to their structural design forms. Universal thermocouples are widely used, so they are usually chosen. The material selection for protective tubes mainly considers the atmosphere, temperature, flow rate, corrosion and friction of the tested medium, as well as the chemical adaptability, pressure resistance, stress resistance, response speed and cost-effectiveness of the material.

Then, the diameter, wall thickness, length, airtightness, and fixing method of the protective cover can be determined based on the actual development situation such as the structure and installation location of the tested object. Here, attention should be paid to both wall thickness (which determines wear resistance) and heat capacity (which determines reaction time). In order to improve the dynamic characteristics of the protective tube, the wall thickness of the protective tube should be minimized as much as possible.

If it is a high-temperature environment with severe chemical damage, double protection pipes can also be considered. Armored thermocouples are widely studied and applied due to their flexibility, small diameter, wide adaptability, small heat capacity, fast response analysis speed, long service life, and the ability to cut a length arbitrarily, especially in areas with deep temperature measurement points (such as some working temperature points on the top of boiler structures) or bends.

When selecting, the main consideration is the material, diameter, length, and other parameters of the protective tube. High performance and solid-state thermocouple can combine the advantages of ordinary and armored types, with high temperature resistance, fast response, and long service life. The working temperature of thermocouples is 100 ° C higher than that of ordinary thermocouples of the same type, and the response speed is 6 to 8 times faster than ordinary thermocouples. The selection should be comprehensively analyzed and considered, especially for cost-effectiveness.