How to measure temperature in a hard-to-reach place, and even in a dangerous environment - in a hot blast furnace or in a distillation column? For this purpose, a TEP device is used - a thermoelectric converter, or (in common parlance) a thermocouple. Two electrodes made of different materials are connected to the temperature measurement point, united at the end into a common junction, and at the opposite free ends of the thermoelectrodes the potential difference is measured, from which the temperature is ultimately calculated.
The problem is that the thermoelectrodes themselves change their physical properties in an aggressive environment. And, you may not notice how the sensor starts to "lie", but its operation depends on, say, the fate of a huge metallurgical unit, which needs to be started and stopped for several days.
In the laboratory of technical self-diagnostics and self-control of devices and systems at SUSU, a self-diagnostic TEP has been developed, which allows for timely detection of an increase in measurement error, as well as avoidance of additional technical inspections and calibrations.
The invention will be presented as an exhibit at the international exhibition INNOPROM'24 in Yekaterinburg.
The laboratory sample of the device consists of a set of sensor electrodes, an information-processing unit and a small monitor.
Each TEC has four electrodes, not two like in a conventional thermocouple, "shares the secrets of the technology with Ivan Fedosov, a junior research fellow at the laboratory.
"We use combinations of chromel-alumel-chromel-copel or chromel-alumel-nichrosil-nisil for temperatures up to 1200 degrees Celsius. The temperature is measured synchronously for each pair of TECs, and a weighted average of these values is displayed on the screen. In addition, due to the developed self-diagnostics algorithm, the user is informed of the measurement status: confirmed (error within tolerance), oriented (error exceeds the specified level, but measurements can still be taken into account), and unreliable. In the latter case, the error is large, which means that the sensor has significantly degraded and needs maintenance."
The device has undergone laboratory tests, and the results are encouraging: temperature measurements become 2–5 times more accurate than traditional thermocouples, and the device’s drift towards unreliability is detected 40% earlier – from the operating time.
The proposed solution is good because, unlike conventional thermocouples, it does not require additional scheduled calibrations, but promptly informs the operator when maintenance is required.
"Our development has already attracted the interest of representatives of “Rosatom” State Corporation and Mechel PJSC," says Vladimir Sinitsin, Deputy Head of the Laboratory of Technical Self-Diagnostics and Self-Control of Instruments and Systems at SUSU. "In fact, representatives of one of Rosatom's enterprises set us this task several years ago, which we successfully completed. Now, negotiations are underway on the industrial implementation of our TEP."
Scientists from the laboratory of technical self-diagnostics and self-control of devices and systems of SUSU are thinking about improving the device so that it would also have the ability to self-correct. Then no additional calibrations will be needed at all. However, for this option it will be necessary to accumulate a knowledge base and connect artificial intelligence. For now, these are just plans for the future.
To say more, from July 8 to 11, the developers will present the device at the largest technical exhibition in Ural, INNOPROM, and hope to attract the attention of representatives of the energy and metallurgical industries.