Types of Temperature Measurement Using Optical Methods The contribution does not include comparison of other optical methods of temperature measurement, such as thermovision. The paper focuses only on optical fiber methods of temperature measurement. One of the tasks of the paper is to present possible ways of evaluating temperature data. The individual principles of temperature measurement using optical sensors also require their own ways of converting the optical signal to the measured temperature in degrees Celsius. The use of fiber sensors for temperature measurement is possible using several physical principles which are described in the individual chapters of this text. The use of fiber sensors also offers the possibility of galvanic isolation, which brings the possibility of use in the chemical industry and various explosive environments. It is possible to use optical methods using optical fibers and the principles of blackbody radiation, luminescence in crystals, refractive index phenomenon in the fiber Bragg gratings, or phase shift of two coherent beams in interferometric sensors.
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In applications where such electrical interference can be expected, it is advisable to use other nonelectrical temperature measurement methods. When designing the measuring chain, account must be taken of the adverse effects of electrical and magnetic disturbances on metallic conductors between the actual temperature sensor and the evaluation unit that converts the signal from the sensor to the amplifier or analogue digital converter. Their typical property is low levels of electrical current or voltage. In a standard way, however, metallically attached thermocouple or resistive sensors, bimetallic, extensible in volume, and other principles which are connected to the measured object so that they touch it or are located in a space where a given ambient or general fluid temperature is measured, are commonly used in measuring applications. By these methods, surface temperatures of bodies can easily be determined. These methods require knowledge of the surface emissivity of the measured bodies.
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There are noncontact measurement methods using emitted radiation of the observed body, known as temperature measurement by thermal cameras. High-temperature measurement points in vehicles. is about a temperature fiber sensor for the aviation industry. An example of temperature measurement using optical methods is dealt with in the article from Bock et al. These are, in particular, points in the exhaust pipe, near catalytic converters, or turbochargers. An overview of some key locations in which the temperature is measured is given in Figure 1. There are a number of areas where it is necessary to measure or at least monitor this high temperature directly. One of the primary users of temperature measurements is the automotive industry. IntroductionĪt present, many fundamentally different ways of measuring high temperatures are used.
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Therefore, there is intensive development of optical and fiber optic methods based on blackbody and greybody radiation, luminescence, fiber Bragg gratings (FBGs), and interferometers. These may be areas with high electrical and magnetic interference or critical areas.
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Optical fiber sensors can be used in cases where standard electrical measurement methods cannot be used. Since the measuring chain is a functional combination of optical methods, optical fiber properties, and other photonic elements together with control electronic circuits, it is necessary to find a suitable compromise between the chosen measurement method, measuring range, accuracy, and resolution. The aim is to evaluate the current research of temperature measurements in the interval from temperature close to 0 up to 1000☌. The paper deals with the overview of fiber optic methods suitable for temperature measurement and monitoring.