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Contactless temperature sensing is state of the art and essential part of countless applications in the field of process control and automation. This contribution presents the case of a nondestructive thickness measurement method for polymeric coatings on concrete ground. Two pyrometers and a low-cost infrared camera were taken into account. The particular measurement results were compared with those of a more sophisticated infrared camera. It was found that the low-cost infrared camera has a lower noise level than the pyrometers, even for a single pixel. The opportunity to average over a large number of pixels and to establish a bias correction enables a further noise reduction by almost factor of 10.
Furthermore, the temporal resolution of the infrared camera was investigated by means of a well-defined thermal oscillation. It could be demonstrated that the averaged time stamps are correct and the requirement of a Minimum framerate of 50 Hz is met. Finally, the temperature transient on a polymer coated concrete block during and after a 10 s heating period was recorded with a pyrometer and the infrared camera. This experiment confirmed the suitability of the camera for the intended measurement method.
The contactless measurement of temperatures with pyrometers is state of the art and a number of different commercial devices are available. Alternatively, these temperature measurements can be performed by means of infrared cameras. In light of permanently falling costs, the application of IR cameras simply as contactless thermometers appears to be an alternative to the use of pyrometers. For a current study, the surface temperature development of a sample has to be measured and recorded with at least 20 Hz sampling rate in a temperature range between 0°C and 70°C and with a temperature resolution of 0.1 K. The absolute value of the temperature is not as important as relative changes. Due to disturbing irradiation in the SWIR and MWIR regions, the sensor should work in the LWIR. We compared two pyrometers and a low-cost infrared camera with regard to the requirements defined above. In this paper we describe the setup, the results and the data evaluation. Both, raw data and post processed data, were considered. Surprisingly, the infrared camera had by far the best performance of the considered devices. Particularly, due to the large number of pixel (160 x 120), the S/N could be reduced considerably compared to the pyrometers. We also studied the stability of the frame rate and the related time steps of the IR camera. Although the frame rate is unstable (running under Windows operating system), the output data for the time steps were found to be correct and the required time resolution was achieved.
The application of IR cameras simply as contactless thermometers appears to be an alternative to the use of pyrometers. For a current study, the surface temperature development of a sample has to be measured and recorded with at least 20 Hz sampling rate in a temperature range between 0°C and 70°C and with a temperature resolution of 0.1 K. We compared two pyrometers and a low-cost infrared camera both sensitive in the LWIR only. Surprisingly, the infrared camera had by far the best performance of the considered devices.
The thermal radiation impact of organic peroxide fireballs is experimentally assessed using an infrared camera. Fireballs are generated while liquid peroxide filled steel drums are subjected to gas burner fire at different heating rates. Three large burning clouds are observed with varying flame characteristics. Thermal radiation properties are assessed by infrared images with the presented methods. Despite of the two-dimensional temperature fields, the flames are treated and characterized as three-dimensional objects. Fireball diameters and heights are calculated based on a representing radiating sphere with the same cloud volume. By the use of the solid flame model and assumptions for emissivity and transmissivity, heat fluxes and thermal radiation doses against distance are predicted. Thermal safety distances are presented based on the maximum irradiance and the allowed exposure time. The validation of the maximum and time-dependent radiation fields is achieved through heat flux sensors in varying distances to the fireball. The results prove the use of an infrared camera and a volume based size calculation to fully assess the thermal radiation hazards of fireballs.