Thermocouple verification devices are generally developing in the direction of automation, and the verification efficiency continues to improve. Automatic constant temperature, automatic recording and generation of verification records and verification certificates that meet the requirements of the national metrology verification regulations have become very attractive and important. Combined with the advantages of fast and accurate computer data processing, the application of the intelligent thermocouple calibration device integrated with the microcomputer system greatly reduces the labor intensity of the calibration personnel and improves the reliability of data processing at the same time.
1. Progress in Theory and Technology
1.1. Multi-zone heating and temperature control technology
By transforming the temperature control method of the tube resistance furnace, the three-stage temperature control method reduces the measurement uncertainty during calibration.
There is a physical partition heating scheme, the heating is divided into three sections and controlled independently, which solves the problem of excessive peak current, obtains a longer central uniform temperature zone, and realizes multiple working modes (long furnace, short furnace and Annealing furnace). There is also a time-sharing patented technology, which divides the heating process into 3 time stages, and solves the problem of excessive peak current by re-series configuration of heating wires in time-sharing heating.
1.2. Short Length Thermocouple
The current technical specification for temperature field test of thermocouple verification furnace is JJF1184-2007 "Technical Specification for Temperature Field Test of Thermocouple Calibration Furnace". The test of the temperature field of the horizontal tube type verification furnace provides the basis, and also provides the standard for the test of the vertical tube type verification furnace and annealing furnace. The specification clearly distinguishes the verification furnace and the short furnace.
Traditional measurement equipment and measurement methods are often unable to accurately measure the indication deviation of short thermocouple in high temperature areas.
1.3. Control and Automation
Using the new thermocouple automatic detection mode combined with computer technology, automatic control technology and digital technology, the overall framework of multi-parameter data acquisition, data correction, data storage and report judgment is given, and the thermocouple automatic verification system is further developed. The system runs stably and is easy to operate, which can meet the testing requirements of thermocouple measuring instruments.
1.4. Furnace Technology
A. Enhanced heat radiation technology:
In order to reduce energy consumption and reduce atmospheric pollution, the heating furnace has been enhanced with heat radiation technology using black body technology. In this work, the furnace lining is strengthened by heat radiation materials, the radiation direction of the furnace lining is adjusted, the heat transfer area is increased, the heat loss is reduced, and the heat transfer effect is enhanced. Finally, the uniformity and stability of the furnace temperature are improved. In this case, the energy consumption is significantly reduced.
B. Solution to the problem of high temperature leakage:
The leakage of thermocouple verification furnace under high temperature conditions is almost a common problem in the industry. When the verification furnace verifies the temperature above 1000°C, as the temperature rises, the free electron movement ability in the material increases. High temperature will cause the insulation strength of the furnace tube material to decrease. Because during the thermocouple verification process, it is necessary to replace the thermocouple position of the verification furnace, the leakage problem will not only affect the stability of the heating power, cause the measurement value to fluctuate and affect the measurement results, but also cause problems such as leakage of the verification furnace , seriously threatening the health and safety of operators. Innovate in structural hardware, adopt special structural design, and add a grounding shield to completely solve the leakage problem, and there is no leakage in the entire temperature range measured.
C. Soaking block: In view of the poor temperature field index of the traditional single temperature zone verification furnace, the technical index of the temperature field when the verification furnace is fully loaded does not meet the requirements, and the problem of large fluctuations in the temperature field of the tube furnace during testing. The use of cup-type superalloy uniform temperature block and tube furnace is used together to improve the technical index of the temperature field, reduce the fluctuation of the temperature field, and meet the detection of thermocouple with different diameters.
Related Products: Bare Thermocouple Wire, Temperature Probes
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