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Thermal imaging cameras detect infrared radiation over a variety of applications. All objects radiate infrared radiation or heat that can be detected. Infrared thermography is the process of detecting radiation and generating infrared-based images from it.
The purpose of thermal sensing is to identify temperature gradients and process the images to demonstrate these hotspots. Predictive maintenance is crucial in modern engineering and industry.
In this case, as they are usually early indicators of imminent component failure, hotspots are extremely informative. For instance, the presence of hotspots in insulation components or wires in high-voltage power lines and even transformers will indicate that there could be a fire.
Integrated thermal sensors are also perfect for industrial processes that need temperature control, together with a monitoring system for fire detection and an instant indication of equipment issues.
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Infrared Detection Applications
Infrared is a universal emission for all objects. The example that everyone will identify with is the passive IR camera/sensor, which can detect heat emissions. These emissions come from a range of sources, for instance, sensors can detect hotspots in industrial wastme sites and barrels at risk of fire.
Detecting IR emissions from poorly insulated buildings to increase efficiency and optimize building energy saving is another application. In a process context, smaller sensors are extremely useful.
For instance, monitoring heat timings and variations can prevent refractory and insulation materials from failing. Machines can also adapt their speed or send alerts to assembly line operators accordingly in a factory with heating and cooling steps for its manufacturing process.
As industries embrace digital transformation, accurate thermal sensors are becoming crucial. Process monitoring or manufacturing automation are the most common places to locate thermal sensors in the industry.
What Are They and How Do They Work?
Passive infrared detector systems are small integrated detectors which utilize semiconductor systems to detect emitted radiation and convey the signals produced to a data processing system.
They function by detecting the IR radiation, which is emitted by objects. Infrared enters via the sensor face at the exposed leading face of the sensor. The core of the PIR sensor is made up of a solid-state sensor, which is typically arranged in layers of pyroelectric material.
When they detect IR radiation, pyroelectric materials produce an electrical signal which is augmented for detection and processing. These sensors are usually around 40 mm2, which means they are a good size to be integrated into arrays with other types of sensors or in space-limited areas.
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The Demands for a Good Thermal Sensor
A good thermal sensor has a variety of needs in the competitive market produced by industry 4.0 applications. Typically, sensors should be powerful, small, and unobtrusive. This is due to the extremely strict weight and space constraints for incorporating thermal sensors in new hardware products.
So neighboring sensors can integrate into a detector array and their images overlap and cover a larger area, the key factor is that the sensor should be powerful and able to cover a greater field-of-view.
Thermal sensors are also required to be able to fit into bigger, more complex multiple sensor systems to supply a combined multi-purpose signal. It can also be employed as a motion detector device by configuring the PIR sensor in a differential mode.
This means a signature of two or more pulses at the output of the sensor triggers an alarm indicating the detection of movement when the heat is detected in the line of sight of the sensor.
This places the emphasis on sensor fusion and often needs clever engineering to make sure that different sensing technologies work in harmony with the same detection system.
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TeraRanger Evo Thermal
The TeraRanger Evo family is a range of thermographic sensors that supply great performance in a small and compact device. Designed to integrate into a range of applications across industry, security and the environment, the weight of each sensor module is between 7-9 g.
Depending upon how much area there is to cover, the Evo Thermal sensor module comes with various fields of view, a 90 ° and 33 ° version. The Evo Thermal 33, which has a 32 x 32 resolution, supplies a more detailed image than the 90 version and has a higher sampling rate (14 Hz) and a slightly longer range.
The sensors can perform in many conditions (outdoor, indoor, darkness or bright sunlight) to identify hotspots and temperature gradients. Passive sensors like these can detect human body heat signatures easily at a range of around 13 meters.
The TeraRanger thermal sensor is a modular system that is available in two interchangeable parts, i.e., the back thermographic module and the yellow backboard that supplies the power management and communication, which is suitable for the system. The backboard can incorporate UART or USB interfaces and is ready for OEM integration.
Most PIR sensors possess a range of 10-13 meters and, with a wide field of view, it is easy to see how a few detectors in an array can cover a relatively big space. This is why PIR-based systems are good for monitoring temperature variations in storage areas, industrial heat and fire detection, and controlling heat-sensitive processes.
In pharmaceutical manufacturing, for instance, temperature monitoring is crucial to guarantee product conformity and quality. PIR sensors could be the future of this application. It is anticipated that the future will bring more powerful detectors with wider fields of view and longer ranges.
References and Further Reading
- Corsi C, History highlights and future trends of infrared sensors, Journal of Modern Optics, 2010: 57(18), p 1663–1686.
- Tsai CF, et al. Pyroelectric infrared sensor-based thermometer for monitoring indoor objects. Review of Scientific Instruments. 2003; 74 (12): 5267–5273.
- Passive infra-red detectors, Science Daily, Available at: https://www.sciencedaily.com/terms/passive_infrared_sensors.htm Accessed October 2019.
- Yang D, et al. Passive Infrared (PIR)-Based Indoor Position Tracking for Smart Homes Using Accessibility Maps and A-Star Algorithm, Sensors 2018, 18, 332.
This information has been sourced, reviewed and adapted from materials provided by Terabee.
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