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Infrared radiation thermometers (IRTs) offer advantages over thermocouples, addressing responsiveness and calibration issues. Yet, precise measurements near room temperature remain elusive. A new IRT, sensitive to 3 μm to 11 μm wavelengths, was developed and tested. It employs an uncooled InAsSb photodiode, a transimpedance amplifier, and a silver halogenide fiber optic cable. The prototype accurately measures temperatures from 35°C to 100°C with an integration time of 5 ms, and 40°C to 100°C within 1 ms, exhibiting RMS noise levels below 0.5°C. Calibrated against Planck’s law, it maintains a measurement uncertainty within ±1.5°C. Successfully tested in drilling operations, future versions aim to replace thermocouples in various applications, including electric motor monitoring and material machining.

Temperature measurement plays a critical role in industrial processes, yet conventional methods, like thermocouples, face challenges such as slow responsiveness, calibration drift, and intrusive contact requirements. Addressing these issues, we developed a novel infrared radiation thermometer (IRT) utilizing an indium arsenide antimony (InAsSb) photodiode coupled with a silver halogenide optical fibre. This setup allows for high-speed, non-contact temperature measurement, capable of monitoring near-ambient temperatures in challenging environments.

Our solution leverages the superior sensitivity and speed of the InAsSb photodiode, combined with fibre optics that transmit infrared radiation efficiently over a broad spectrum (3–11 μm). The prototype thermometer achieved impressive results, with a temperature range of 35–100°C and an RMS noise level below 0.5°C. A custom-built transimpedance amplifier optimized signal processing for reliable performance, even at an integration time of just 1 ms.

Testing involved calibrating the device against Planck’s law using a blackbody furnace, achieving a measurement uncertainty of ±1.5°C. The thermometer was further evaluated during drilling trials on polyether ether ketone (PEEK) plastic. The fibre was positioned close to the drill bit, allowing accurate monitoring of tool temperatures during high-speed machining. The system demonstrated excellent performance, even under the thermal and mechanical stresses of the machining environment.

This innovative technology offers a robust, scalable alternative to thermocouples, with potential applications in electric motor monitoring, battery safety, and machining of polymers and composites. Future development will focus on enhancing its temperature range and integration into industrial systems, revolutionizing high-speed, near-ambient temperature sensing across multiple sectors.

This research marks a significant leap in temperature measurement technology. The newly developed IRT addresses critical limitations of traditional thermocouples, offering faster and more reliable readings. This advancement is expected to revolutionize temperature monitoring in various industrial applications. For instance, in electric motor condition monitoring and battery protection, precise temperature readings can prevent failures and extend component lifespans. Additionally, in machining processes, especially with polymers and composites (such as carbon fibre reinforce plastic, CFRP), the IRT can enhance product quality and manufacturing efficiency. By providing a non-invasive, accurate, and rapid temperature measurement tool, this technology will drive improvements in process control, safety, and productivity across multiple sectors.

Emilios Leonidas is a final year EngD researcher in the centre of doctoral training in advanced metallic systems at the university of Sheffield, specialising in the Development of Innovative Instrumentation and Modelling for 21st Century CNC Machining in collaboration with the AMRC and AFRC. He graduated from Bachelor of Engineering in mechanical engineering from Aston university in 2018, where he focused on Automatic Inspection Systems Used for the Maintenance of Rail Tunnels.