Introduction
The application of different factors of radiation, more so in the industrial world is an occurrence whose relevance cannot be underestimated. The use of thermal imaging cameras, a device that is basically used to measure temperature without having contact with the materials constitutes one of such developments (Williams, 2009). In applying the device as a tool for measuring temperature, a number of factors come into play. One of these features includes the level of emissivity of the materials to be put under observation (Volmer, Mollmann & Willey, 2010). The fact that there also exist different procedures for measuring emissivity measures of the different objects cannot be underestimated. Furthermore, the emissivity values of these materials have an impact on the temperature readings for the same objects. It is proper to ensure that proper steps are undertaken while using the device for the various scientific and industrial applications (Modest, 2003).
Thermal Imaging Camera
According to Don Flagan (2007), this is a device used for measuring temperature through non-contact means. These devices have the capacity to perceive any forms of infrared energies, whether released, reflected or transmitted by the various materials on the face of the earth. A Thermal Imaging Camera functions at temperatures not below zero Kelvin. The device helps to convert energy into values that make it possible to read in temperatures. As Williams (2009) puts it, the device is typically a thermo graphic camera. This is owing to the fact that the devices makes user of the infrared radiation to produce images, just as the case is for ordinary cameras. The only difference between the regular cameras and the Thermal Imaging Cameras lies in the use of a specified array of visible light and the application of wavelengths respectively in their operations (Modest, 2003).
The device that is also referred to as TIC is applied in a variety of industrial operations. Some examples of such operations include firefighting, conducting home energy inspections and troubleshooting machineries and electrical structures among other uses. The gadgets are composed of five major component parts i.e. the amplifier, the detector, the display, the signal processing unit and the optic system (Volmer et al, 2010). These parts work together in facilitating measurements mainly in situations where the users consider, largely, the existence of temperature discrepancies and visual indication also required. Considering the non-contact nature of the device, it promotes safety for users by allowing them to measure temperature variations from a safe distance. In indicating the different temperatures as measured by the device, there exist different colors, which the gadgets produce as they detect various degrees of temperatures (Williams, 2009).
Thermal imaging Camera is a feature whose existence, since its invention, is associated with various aspects of military operations and law enforcement (Cverna & ASM International, 2002). Although its use has to a massive degree been associated with firefighting, its use in the field has been frustrated widely. This is blamed on the high costs of the cameras that are fitted within the gadgets. However, its effectiveness as a device for firefighting is obvious. Thermal imaging camera, in its use, is not hindered by the likes of smoke and darkness (Gorbett, 2009). Because of their high capacity to see through smoke and darkness, firefighters are able to rescue victims who cannot be spotted in cases where ordinary cameras are employed (Clausing, 2005).
Emissivity
This refers to the proportion of radiation, which a black substance or any surface releases, and the plank’s law predicted hypothetical emission (Flagan, 2007). Emissivity in relations to the surface of a material has to do with the amount of energy that is released in instances where the surface is viewed directly. According to the laws of emissivity, blacker or duller substances possess a higher level of emissivity, almost close to one. The brighter materials on the other hand are lower when it comes to this measure. Furthermore, the thickness of the materials under observation also serves as a factor for emissivity (Cverna & ASM International, 2002). Optically thicker material possesses a higher level of emissivity while the reverse is true for the optically thinner materials.
Reading Temperature
The reading of temperature among variant material is usually done using the Thermal Imaging Cameras (Gorbett, 2009). These gadgets, in real sense, do not visualize the temperatures of the object under observation. They, on the other hand, capture energy, in infrared form, from objects to their surroundings (Modest, 2003). By doing this, these devices help generate instant images in a color palette (Volmer et al, 2010). As the color palettes are produced, materials, which have cooler temperatures, produce duller colors while those with higher temperatures appear brighter in color.
Thomas Williams, in his book, “Thermal imaging cameras: Characteristics and performance” indicates that these devices capture the infrared energy which is produced when molecules and atoms within the materials vibrate, a behavior which typifies that of visible light. This enables the generated energy to be reflected and refracted. The energy is than absorbed and released by the materials (Flagan, 2007). The degree of movement between the atoms and the molecules determines the resultant temperature of the materials under observation. Here, the atoms and molecules that move faster generate higher temperatures than the relatively slower ones (Cverna & ASM International, 2002).
Also of importance to note is that these devices allow for the measurement of temperature in instances where regular sensors cannot serve. An example of such instances is where measurement ought to be taken on materials that move or are too hazardous to touch. Additionally, the devices are considered suitable for measurement of temperatures on objects that are significantly distant (Volmer et al, 2010).
Measuring Emissivity
Different methods can be used in determining the levels of emissivity of materials (Flagan, 2007). For instance, one can employ devices like thermo couples in determining the actual temperature of one material. The step that follows would include altering the emissivity settings of the object to find the most appropriate level of emissivity for the material (Volmer et al, 2010).
In cases where the objects have a considerably low temperature, covering the field of view of the object would be imperative. Here the material can be masked using a piece of tape (Williams, 2009). The temperature of the covering tape should them be measured and recorded. This should be followed by measuring the temperature of the adjoining areas on the material. The emissivity settings would then be attuned to match that which was used on the actual material (Modest, 2003). The figure that is obtained would therefore become the accurate emissivity for the object under observation (Cverna & ASM International, 2002). In situations where one can coat parts of the surface of the very material, the kind of paint put to use ought to be dull and black, having an emissivity value almost as high as 0.98. This would serve the same purpose as the masking tape would.
The general procedure for measuring emissivity includes selecting a location for conducting the procedure followed by the measurement of the apparent temperature of the environment. The target material would then be covered with another material before the object under observation is heated evenly. After this, the temperature of both the target material and the covering material would be noted. The emissivity value of the material would then be adjusted to achieve the real absolute emissivity of the object under observation.
Effect of Emissivity Value on Temperature Reading
Accuracy in temperature measurements especially in scientific and industrial application is a very imperative phenomenon. The process of achieving this goal is in many cases achieved by use of the emissivity value of materials. In order to measure the actual temperature of an object, knowledge of the emissivity value of the object is mandatory (Cverna & ASM International, 2002). This measure also has to match up with the determined radiant temperature. Determining the actual emissivity value of an object is however not as easy as it may seem. The ever-changing value of the measure owing to the dynamic nature of the phenomenon is responsible for this. Further, the heat cycle makes it impossible for the emissivity figure to remain constant for the various objects.
Emissivity, just like in the case of temperature, is determined by the wavelength applied while operating the Thermal Imaging Camera (Cverna & ASM International, 2002). Because of this, it is important that one possesses the knowledge of all the parameters to the instruments used in determining the emissivity value. Such values as bandwidth and wavelength have to be clearly monitored to avoid discrepancies in figures (Williams, 2009).
Failure to do this would comprise the outcome of the entire activity, as the figures obtained would not reflect on the actual measurements of the emissivity value and therefore the temperature of the target object. It would therefore be of significance to those involved in measuring emissivity to understand that, only a limited number of objects have static emissivity values (Volmer et al, 2010).
As Clausing (2005) indicates, thermal radiation is a substance, which all materials do release. However, the nature of the materials coupled by their temperatures determines the amount of radiation that can occur within them. For instance, radiations of considerably long wavelengths are obtained under lower temperatures. Steel for example becomes considerably less emissive where the transmission rate for the radiations is at zero. Therefore, it will appear cooler that it should actually be in such an environment. Here, what holds is, emissivity values, depending on their levels of accuracy, have an edge in determining how accurate temperature measurement for given materials are (Modest 2003).
Conclusion
According to this discussion, the significance of thermal imaging cameras and the aspects of emissivity are of massive importance in both the industrial and scientific world among other fields. The use of the thermal imaging cameras in measuring temperatures for cases of possible hazards, distant objects or non-contact scenarios is also obvious (Cverna & ASM International, 2002). Additionally, the emissivity values, which are measured using a variety of approaches, are important in achieving accuracy while measuring temperature in objects. Proper capture of the emissivity levels is mandatory in ensuring accuracy when measuring temperatures of objects (Modest 2003).
References
Brewster, M. Q. (1992) Thermal radioactive transfer and properties New York: Wiley
Clausing, T.L (2005) Emissivity: Understanding the Difference between Apparent and Actual Infrared Temperatures, Washington: Fluke Corporation
Corbett, G. P. (2009). Fire engineering’s handbook for firefighter I & II. Tulsa, Okla: PennWell
Cverna, F, & ASM International (2002) ASM ready reference: Thermal properties of metals. Materials Park: ASM International
Flagan, D (2007) thermal Imaging Cameras: Principles and Practice, Burlington, Massachusetts: Jones and Batlett Learning
Modest, M (2003) radioactive heat transfer, Amsterdam: Academic Press
Vollmer, M, et al (2010) Infrared thermal imaging: Fundamentals, research and applications. Weinheim: Wiley-VC
Williams, T. L. (2009). Thermal imaging cameras: Characteristics and performance. Boca Raton: CRC Press
