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Thermal Nanosensors
Published in Vinod Kumar Khanna, Nanosensors, 2021
What parameters determine the spatial resolution of the tip? Spatial resolution of a silicon-micromachined thermal profiler (SMTP) depends on the Seebeck coefficient of the TC and on the thermal impedance of the probe shank, as well as on operating conditions, such as temperature bias, air gap, and the sensitivity of the interface electronics. For a 1 μm × 0.5 μm tip and a 0.1 μm long air gap, the spatial resolution and the device noise equivalent temperature difference (NETD) have been theoretically estimated as ~3.33 nm and ~0.1 mK Hz−1/2, respectively. NETD is a measure of the sensitivity of a detector of thermal radiation. It specifies the amount of radiation required to produce an output signal equal to the detector’s own noise (due to inner component heat). Thus, it specifies the minimum detectable temperature difference. In general, detector cooling is required to limit the detector’s own noise and to improve the NETD.
Introduction
Published in Yasmina Bestaoui Sebbane, Intelligent Autonomy of Uavs, 2018
UAVs equipped with high-resolution thermal cameras can graphically depict energy inefficiencies and identify wet insulation in the roof or elsewhere by showing temperature variations within the building surveyed with great efficiency [125]. Roof inspection with thermal infrared cameras is typically performed to detect and locate areas of wet insulation. This non-contact and non-destructive method provides a fast, accurate and inexpensive way to locate areas of wet insulation and potential leaks. Two important imagery specifications to consider for UAV thermal infrared roof inspection to produce usable imagery are thermal sensitivity and image resolution. The thermal sensitivity or noise-equivalent temperature difference (NETD) is the measurement of the smallest temperature difference that a thermal imagery can detect in the presence of electronic noise. The lower the thermal sensitivity, the more detailed and less noise present on the thermogram. Highly sensitive (low-NETD) thermal imagery shows more temperature differences, and thus more patterns. Image resolution is important for capturing clear images from a distance. High resolutions are needed when observing the roof from greater distance, such as in a flyover.
Temperature and heat flux measurements
Published in Stefano Discetti, Andrea Ianiro, Experimental Aerodynamics, 2017
The NETD is defined as the temperature difference that produces an output equivalent to the peak-to-peak noise from a uniform background temperature field. The procedure for calculating the NETD is given in [68]. It uses a blackbody target at temperature T0 behind a background target plate at temperature T, with an aperture not exceeding a tenth in height and width the dimensions of the plate (Figure 6.20). Denoting with ∆V the peak-to-peak (standard deviation) noise detected when measuring the uniform background (by closing the aperture with a cover of the same properties) and with V − V0 the output measured observing the blackbody target through the aperture, the S/N ratio is (V − V0)/∆V and the NETD can be calculated as NETD=T−T0S/NTypical NETD values are of the order of 100 mK for uncooled detectors and 10 mK for cooled devices. The NETD of an actual instrument is usually quote by the manufacturer. Periodic measurements of the NETD are a useful method to perform sanity checks of an IR camera and monitor eventual drifting with time.
Distance and camera features measurements affect the detection of temperature asymmetries using infrared thermography
Published in Quantitative InfraRed Thermography Journal, 2022
Álvaro S. Machado, Mar Cañada-Soriano, Irene Jimenez-Perez, Marina Gil-Calvo, Felipe Pivetta Carpes, Pedro Perez-Soriano, Jose Ignacio Priego-Quesada
FPA influences asymmetry determination, but it is important to note that even cameras with similar FPA may provide different results. The Noise Equivalent Temperature Difference (NETD), which quantifies the thermal sensitivity of the camera and also refers to the ability of the system to detect small temperature differences within the image, can be a source of differences between cameras with similar FPA. The lower the NETD value, the lower is the noise and the smaller is the temperature differences that can be detected by the camera in an image [29].
Process-integrated steel ladle monitoring, based on infrared imaging – a robust approach to avoid ladle breakout
Published in Quantitative InfraRed Thermography Journal, 2020
Biswajit Chakraborty, Billol Kumar Sinha
The action of the ladle monitoring system is automatic detection of hotspot on ladle surface and archiving of ladle thermal images for processing. The thermal trending of the processed images of any particular ladle can help in assessing the condition of refractory lining of that ladle and help in deciding whether the ladle should remain in circulation or should be taken out of circulation for relining. Considering the presence of mainly CO2 and water vapour in the atmosphere of the commissioning site, the long-wave infrared camera is selected since the atmosphere tends to act as a high-pass filter above 7.5 µm. In our system, long-wave (7.5 µm to 13 µm) uncooled microbolometer-based FLIR A315 GigE compliant 60 Hz thermal cameras with a resolution of 320 × 240 pixels are used. A lens with 25° Field of view (FOV), 18 mm focal length and 0.4 m minimum focus distance is used for imaging. Gigabit Ethernet Cameras are used in applications that require multiple cameras, fast data transfer rates up to 1000Mb/s or long cable lengths. The detector time constant which is also referred to as integration time or exposure time of the infrared camera is 12 ms and the accuracy of measurement is ±2% of reading for FLIR A315. Noise equivalent temperature difference (NETD) is an important parameter of a thermal imager and is a measure to distinguish between very small differences in thermal radiation in the image. For FLIR A315, the NETD is 50 mK. The calibrated temperature range for the camera is 0–1200°C. The calibration information of the thermal imager is required for validation of the measured temperature data. Primarily every camera comes with a calibration certificate which is NIST (National Institute of Standard and Technology, USA) traceable. G. Machin, R. Simpson and M. Broussely [13] discussed the calibration, traceability and validation of thermal imagers in details. The manufacturer of the infrared camera usually recommends annual recalibration of the thermal imager where each camera should be recalibrated by a blackbody radiator in a laboratory where NIST traceability can be obtained.