Thermal imaging sensors convert infrared (IR) radiation produced by an object in the form of heat into a visible light image, which is otherwise invisible to the naked human eye.
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Recently, thermal imaging sensors have been applied in various sectors for industrial inspections. Here, we discuss the use of thermal imaging sensors in industrial settings and explore the technological intricacies associated with their application.
Introduction to Thermal Imaging Technology
Every object emits heat to a certain extent as long-wavelength IR radiation, which is otherwise invisible to the naked eye. Thermal imaging sensors convert the emitted IR radiations into visible-light images.
The information collected using the thermal imaging sensors is processed to fetch a graphical output with a temperature distribution across the object of interest. Thermal imaging sensors allow for the measurement of temperatures between -20 °C and +1500 °C.
In addition to identifying objects in dark or dense smoke environments, thermal imaging sensors can be used to measure temperature differences. However, these sensors cannot image objects that absorb long-wavelength radiation, such as glass and water. Materials such as glass are poor conductors of heat and water blocks IR radiation.
Although thermal imaging technology was initially limited to defense- and government-funded applications, it has gained significant importance in other sectors over the past few decades. Growing awareness of this technology has garnered attention for maintenance and electrical troubleshooting in industrial settings.
The demand for thermal imaging sensors to detect fever in humans has surged substantially during the onset of coronavirus disease 2019 (COVID-19). However, these sensors can only detect the surface skin temperature.
Working Principle of Thermal Imaging Sensors
The most commonly used sensors in thermal imaging include photovoltaic and photoconductive sensors because of their quick response and sensitivity to IR radiation that falls between 2-14 µm. The output from a series of IR detectors, targeted at an assembly of red light-emitting diodes, fetches an image output with various intensities of black and red backgrounds corresponding to different temperatures.
More sophisticated thermal imaging sensors have a tripod-mounted detector linked to a computer. These systems use multicolor displays (up to 15 colors) to show different temperature bands. Thus, the heat distribution around an object is graphically represented and displayed as colored bands.
Importance of Thermal Imaging Sensors in Industrial Inspections
Thermal imaging sensors have been used for industrial safety and accident prevention, and they help detect temperature changes. The roles played by the thermal imaging sensors in industries are as follows:
Detecting Electrical Overheating
Electrical system overheating can lead to equipment failure and explosions. Hence, regular inspections to maintain electrical safety are crucial in industrial settings.
Although conventional inspection methods are ineffective in continuously detecting hazards, thermal imaging sensors can help combat this limitation by detecting temperature changes. These sensors detect hotspots with temperatures higher than those of their surroundings, assisting engineers in taking corrective actions to prevent equipment failure or fire.
Mechanical Failure Identification
The mechanical equipment used in industrial settings can wear out, leading to malfunctioning over time. For instance, an increase in temperature is caused by excessive friction in the shafts, bearings, and gears.
Identifying mechanical failures before they occur is crucial for ensuring industrial safety. To this end, thermal imaging sensors detect temperature changes in the machinery. Detecting the temperature increase via hotspot detection helps engineers take corrective actions, including alignment, lubrication, or replacement of damaged components.
Fire Prevention in Storage
In some industries, stored materials can lead to fire ignition, causing damage to property and posing a significant risk to workers. Thermal imaging sensors can help identify potential hazards in industrial storage areas by detecting the temperature of the stored material. Some materials are extremely sensitive to moisture and heat and can react violently, leading to spontaneous combustion.
Integration of Thermal Imaging Sensors with Other Technologies
Integrating thermal imaging sensors into drones enables operators to observe invisible temperature data. Thermal imaging sensors deployed on drones allow for collecting radiometric data, even at hard-to-reach locations. Thus, thermal imaging sensor-integrated drones are accessible and cost-effective for a wide range of applications, from scanning manufacturing defects to surveillance and security.
The Internet of Things (IoT) has transformed healthcare systems by integrating technological, economic, and social aspects. During the COVID-19 pandemic, IoT-powered drones were employed to deliver medications and critical medical equipment to individuals in developing countries. These drones have also been used to sanitize public spaces and detect symptoms associated with the virus.
Recent Studies
An article published in Applied Optics described the development of a compact and cost-effective two-dimensional thermal imager with a combined complementary metal-oxide-semiconductor (CMOS) camera and a compact spectrometer.
The constructed system was employed to measure the melt pool during the laser cladding production (an additive manufacturing technique) of a highly wear-resistant coating constituting tungsten carbide particles in a nickel matrix.
The results revealed a sequential change in the flow rate of tungsten carbide powder from 5 to 27 g/min using powder feeder programming, resulting in variations in the melt pool dimensions and temperature maps during the cladding process.
Another article published in Sensors reported the construction of low-cost embedded electronic hardware, comprising both normal and thermal imaging sensors, to detect water leakage in minimal time in agricultural fields. The developed system was used to collect the required data and installed on a mobile agricultural robot.
In addition, a software system was developed for low-cost embedded systems and personal computers for faster detection and decision-making processes. The manual performance of the field experiments demonstrated the good performance of the developed system.
Conclusion
Overall, thermal imaging sensors have had a significant impact on various industries, especially in industrial settings, by utilizing infrared radiation emitted as heat from previously invisible objects. These sensors have improved the safety, maintenance, and inspection processes.
They can detect anomalies, such as electrical overheating, mechanical failures, and potential fire hazards in storage areas. However, this technology has limitations, such as its inability to image materials that absorb long-wavelength radiation, such as glass and water.
Despite these limitations, technology is expected to continue to evolve and become more accessible, leading to increased contributions to industrial efficiency, safety, and problem-solving across multiple sectors.
References and Further Reading
What is Thermal Imaging? Working Principle, Block Diagram and Application. Available at: http://electricalworkbook.com/thermal-imaging/
Thermal Imaging Takes the Temperature of New Applications. Available at: https://www.photonics.com/Articles/Thermal_Imaging_Takes_the_Temperature_of_New/a66776
Türkler, L., et al. (2023). Detection of Water Leakage in Drip Irrigation Systems Using Infrared Technique in Smart Agricultural Robots. Sensors, 23(22), p. 9244. doi.org/10.3390/s23229244
Grishin, M. Y., et al. (2023). Combining thermal imaging and spectral pyrometry for express temperature mapping in additive manufacturing. Applied Optics, 62(2), pp. 335-341. doi.org/10.1364/AO.478113
3 Roles of Thermal Imaging in Industrial Safety and Accident Prevention. Available at: https://www.infiray.com/3-roles-of-thermal-imaging-in-industrial-safety-and-accident-prevention.html
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