Instruments for radiometrically determining temperatures are calibrated against blackbodies. The characteristics of blackbody cavities, especially their temperature uniformity and effective emissivity, are important in establishing traceability to the International Practical Temperature Scale. When used with non-black surfaces, the radiation thermometer indicates an apparent temperature. The user must recognize how to utilize information such as target emissivity and temperature of the surroundings to properly infer true surface temperature from the indicated value.

Decisions in our legal system are made by laymen. Even the most technical and complex cases are heard and decided by a judge or jury who may very well have no expertise on the questions which confront them. As a result, our legal system permits experts to explain complex phenomena to the fact finder and even to express his opinion on the issue which the fact finder ultimately has to decide. For example, an expert may explain not only how an airplane accident occurred, but also may testify that someone was at fault.

With the continued growth of legal activities involving litigation, lawsuits involving technical matters may be very complex. Expert witnesses are often hired by both plaintiffs and defendants to help clarify and simplify technical merits of a case in order for the jury to make an educated decision. The usage of infrared thermography in legal matters has also been growing. This paper reviews several areas where infrared thermography has been utilized in legal matters. These include analysis of building defects, fire analysis and equipment failures. Expert witness qualifications, test procedures and analyses are discussed. The role of industry and governmental standards is reviewed. Opinions from the infrared thermographic expert should be unbiased, factual and within the area of qualification of the expert.

As an overview, this is a consideration of a group of inorganic materials which transmit IR light in that region of the electro-magnetic spectrum from about 1 micron to beyond 25 microns. In addition to the transmission, some properties in visible light will be mentioned as well as refractive index, hardness, and thermal conductivity.

In the last few years, the sensitivity of Forward looking infrared (FLIR) devices has increased considerably. The requirements on the testing stations in production and in the field have changed accordingly. The heart of the test station is the infrared source, usually a "differential blackbody". In order to make much more accurate measurements, the source must be such that: 1. Its temperature and emissivity profiles are as uniform as possible. 2. The differential temperature is as stable as possible in the short term (hours) and long term (months). 3. The recalibration procedures are as simple as possible, reliable and traceable to an international standard. 4. The differential temperature is measured and displayed with high resolution (of the order of 0.001C). CI has recently developed a new differential blackbody source, based on very stable electronics, and microprocessor based technology, in an effort to meet the modern requirements for this type of instrumentation. The microprocessor is especially useful to automatically take into account systematic temperature gradients between the probe used to control the temperature and the emitter surface, or the emissivity differences between the emitter and reference plate, if needed. CI has also developed new radiometric calibration and uniformity test techniques, which use a particular version of its telescopic radiometers. These radiometers can measure temperature differences of the order of millidegrees near room temperature, and are also based on a special microprocessor programme which translates the detector signal to a temperature reading. This paper will describe some of the common problems encountered in the differential blackbodies, and to some extent, the work recently performed at CI to solve them. A radiometric technique to measure the temperature uniformity and stability will also be described.

Four references and two arrangements are described for cavity emissivities greater than one. There are different types of emissivities, but all depend on a radiometric output divided by what that output would have been if it had come from an ideal blackbody. Cavity emissivities can be greater than one for a nonisothermal cavity when the temperature of the reference blackbody is selected to have a lower value than the temperature of most of the cavity wall surface.

Too often the process of thermal image analysis is performed without any thought as to why and how we reach certain conclusions regarding image content. A scene is observed, inferertces made, and judgments rendered regarding the identity of objects and background that compose the scene. The purposes of this paper is to formalize the process of thermal image scene analysis using an explicit model consisting of surface and subsurface features that may be observed in any scene. The model is presented along with a comparison of the differences between thermal and visual scene analysis. Conclusions are made with regard to the application of this model to the use of artificial intelligence for automatic recognition of thermal imagery.

It is demonstrated that the temperature of a thermal radiator can be determined by curve fitting techniques using multiple spectral radiance measurements without prior knowledge of the emissivity of the source. This new passive measurement technique assumes only that a smooth function exists between spectral emissivity and wavelength. The spectral radiance values are fitted to a Planck radiation law relation to yield the temperature of the source. Error analysis shows that relative errors in the temperature measurements are generally an order of magnitude less than in the spectral radiance measurements and in the simultaneously calculated spectral emissivity values. Computer simulations are included which show the effects of varying different parameters, such as the number of data pairs, the wavelength range, the spectral emissivity behavior, the source temperature, and the measurement noise, on the accuracy of the temperature determination. Experimental confirmation of this technique is presented showing temperature measurements within 1% of the actual temperatures on a platinum surface within a temperature range of 1273-1724 K.

High temperatures generated during rapid thermal reactions require techniques to index time and calibrate high temperature. The technique used to establish time required the design and fabrication of a time indexing constant temperature source to measure reaction times. A unique black body source was used for high temperature calibration. These techniques and their applications will be discussed.

Two applications of thermography for testing and development of turbomachinery components are described: (1) Fabrication defects in the cooling system of internally cooled turbine blades are detected by transient heating of the blade and measuring its surface temperature distribution by an infrared imaging system. Defects like blocking, narrowing, widening and mispositioning of cooling channels can clearly be identified by the disturbance of the transient surface temperature distribution of the blade. (2) To improve the cooling configuration of turbine blades the cooling effectiveness over the total blade surface must be determined under test conditions similar to those in the turbomachine. The infrared measurement of blade surface temperature distributions in an hot air cascade and the method, to correct the infrared intensities for radiation reflected at the measuring surface, are illustrated in an example.

A characteristic piece of a solar array herein referred to as a Q-board was placed in a cryogenically cooled vacuum chamber with exposure to radiation from a solar simulator and subjected to a series of test conditions. The test conditions simulated failure modes which caused certain rows of the cells to be reverse biased. As a result of these test procedures, some of the cells on the solar array increased in temperature. Surface and bulk temperatures were monitored and periodic solar cell performance curves generated to evaluate degradation of the cells, if any, during the test. The bulk temperatures were measured by thermocouples bonded to the Q-board. The surface temperatures of the Q-board were monitored through a heated Potassium Chloride (KC1) cha bet viewing port by an AGA780 thermovision unit and digitally recorded. Since the array had an emmissivity of less than 1, (c -.8) and could only be viewed by the detector through the heated KC1 window, it was necessary to calibrate the detector using a blackbody radiation viewed through an intervening KC1 window. Compensations were made to account for the radiative and reflective contribution from the KCL window. Correlation of the measured temperatures to the theoretical or predicted values are discussed as well as the method used to calibrate the AGA detector and compensations made.

This report describes the instrumentation system, the calibration theory, and the error analysis of an experiment designed to measure front surface temperatures of the Barstow Solar Central Receiver panels. The instrumentation system uses an infrared detector, imaging peripherals, a collimator, and a 30 power telescope. The unique feature of this application is the large distance (200 m) between the detector and the target (1.27 cm diameter tubes). Sources of thermal radiation other than the target are found to contribute heavily to the input signal. Thus, the calibration scheme must specifically account for these background or environmental effects. During the data acquisition, two blackbody radiators at known temperatures are referenced periodically, and their output signals are used to define the calibration curves. These curves are valid as long as the environmental effects remain unchanged. The error analysis uses the Root-Sum-Square (RSS) technique for evaluating random errors. The biased errors are assumed to stem from spatial resolution problems, and are addressed using the optical transfer functions of the system. Data analysis and interpretation are covered in Part II, Receiver Evaluation.

Front surface temperature measurements made on the receiver at the 10 MWe Solar Thermal Central Receiver Pilot Plant near Barstow, CA are described. The receiver consists of 24 panels, each 45 feet long by 35 inches wide. Each panel is comprised of seventy half-inch diameter Incoloy tubes painted with an absorptive coating. Solar radiation, focused onto these panels, produces steam from water flowing through the tubes. The panel surface temperatures are needed to verify thermal-hydraulic computer codes used for performance predictions. Indications of large temperature gradients and fluctuations on a panel are needed in determining thermal stresses. The measurements were made using a commercial infrared camera/detector coupled with a 30X telescope to provide adequate resolution over large distances. The telescope and detector were located 660 feet from the receiver. Temperatures of one receiver panel were recorded during quasi-steady receiver operation. The trends of the results are corroborated with data obtained from receiver panel back surface thermocouples. The transient behavior of a panel section was recorded during a receiver shutdown, during which the focused radiation was quickly removed from the receiver. Results of the quasi-steady panel scan and the transient observation are presented.

Infrared thermography has been used to study spatial temperature distributions on heterogeneous catalytic surfaces under ordinary reaction conditions. Thermograms of supported catalyst wafers, gauzes, and foils, obtained under steady-state and oscillatory conditions, showed the presence of marked thermal variations on the surface of the catalysts. In the case of supported catalysts, large temperature variations were observed under steady-state conditions, and thermograms show that hot spots with high activity seem to dominate the process. In such a case, conventional calculations of specific reaction rate and turnover numbers with the implicit assumption of spatial uniformity would be in error. Thermographic observation has shown that spatial variations of the rate of reaction on catalytic surfaces seem to be greater than was previously suspected, and the implications, both practical and theoretical, may be far reaching. This work was the first to use thermal imaging techniques in the study of spatial phenomena on catalytic surfaces under steady-state and dynamic conditions. The technique yields valuable information and is potentially a useful and inexpensive addition to the array of tools available to researchers for the understanding of catalytic processes. Thermography may be useful in the testing and screening of catalysts, and appears to be the only generally useful method for obtaining spatial information on catalytic surfaces under ordinary reaction conditions.

To adequately examine the subsurface condition of a composite structure, a thermal imaging system (thermography) was comparatively evaluated with existing nondestructive inspection techniques and has proven to be more expeditious and ultimately more cost effective. Thermography is easily adapted to composite manufacturing, particularly in the rubber insulating materials, because of their strong transfer thermographic characteristics. Temperature conditioning is a standard process in the manufacturing of composites, which ensures component homogeneity and structural stability; thus, the desire to alter the temperature of a specimen from room ambient is a standard and uncompromising task.

A new measurement procedure, based on use of a scanning radiometer system and laser heating apparatus, has been applied to evaluate thermal conductivity of a 7075-T651 plate aluminum alloy specimen. This commercially available radiometer system operates on the principle of differential temperature measurement, where the temperature increments are produced by applied stress or heat. It also features digital data processing and display of thermographic images. The thermal conductivity value determined by this procedure was compared with a reference value for the material, and the two agree within the estimated error bounds of the methods.

Understanding the influence of fundamental welding parameters on the distribution of the heat flux on the weld and the resulting weld bead morphology has become increasingly important with the escalating emphasis on automated control of the welding process. The arc heat source distribution at the work piece has been studied using the underside infrared signature. Arcs were struck on a thin anode section ranging from 0.5 to 2 mm in thickness. Results from both experiments and calculations suggest that the arc heat input can be readily characterized using the IR thermogram. In addition, other properties such as weld pool cooling characteristics and solidification processes can be determined using this method.

A unique technique for microwave wavefront measurement using infrared (IR) detection for the purpose of wavefront reconstruction is presented. This paper extends previously reported IR detection results of microwave interactions, to the measurement of tangential electric or magnetic field magnitudes using resistive paper or a ferrite-loaded material respectively. Partial phase information is obtained by using subapertures, coated for IR detection, each oriented in the direction of maximum power transfer, which provides noisy phase difference measurements. This limited spatial relative phase information is used along with the measured magnitude to reconstruct the incident wavefront. Two previously reported algorithms are described for this reconstruction. The first algorithm uses relaxation techniques while the second more general algorithm is a Kalman filter type iterative algorithm.

Dynamic monitoring of steam trap and steam coil surface thermal patterns can indicate steam system malfunction. Condensate lines at atmospheric pressure showed a temperature fluctuation of several degrees due to a momentary pressure increase caused by a properly functioning steam trap cycling. A malfunctioning trap showed no such increase. This effect decreases with increased condensate line pressure. Steady state observation of the tempera-ture drop across steam traps could not reliably distinguish good traps from bad. Dynamic observation of steam coil surface temperatures showed a typical 10% to 15% loss of heating surface due to gas blockage. Purging by installing an air vent provides only temporary relief.

The detection of sub-surface defects and structures, by thermal pulse video compatible thermal imagers, ie beginning to complement the slower methods of ultrasonic scanning and in some applications to surpass them. In principal a short pulse of radiation is emitted from a xenon flash tube and is absorbed by the surface of the material under inspection. This energy diffuses as heat through the material and sub-surface features are revealed as variations in surface temperature, either on the far face or near face, by a scanning infra-red camera. The promise of thermal pulse thermography lies in its ability to inspect materials for defects and quality with great speed and without physical contact. Other methods of applying heat are currently being investigated.

The non destructive techniques of radiography, ultrasonics or eddy current are today generally accepted. Methods, basing on the variation of the temperature distribution (Thermogrammetry) always has been regarded as difficult. However, a method which requires no contact other than thermal transfer and which also can be applied if the object only can be accessible from one side, is very important. Developments for solutions to these difficulties has been continued. By using a THV- system in conjunction with a TV monitor ano today's computer technology, hitherto inaccessible effects can be recorded and evaluated.

Electronic infrared thermography allows fast and non-destructive measurements of temperature distributions of encapsulated solar cells on a panel under various operating conditions. Differences in the performance of the individual cells can be visualized and so called "hot spots" in the panel (due to partial shadowing, etc.) can be analyzed. IR image analysis was also used to determine the IR emissivity of different types of solar cells. This is one of the important criteria for the evaluation of the electrical-thermal behaviour of a cell for photo-voltaic or combined photovoltaic thermal applications. We designed a portable IR measuring system having both on-line and off-line interfacing possibilities with a minicomputer for image processing and analysis. During field measurements, the composite video signal of the IRT system is recorded on a video cassette. For analysis, the thermal images can be visualized on a TV moni-tor and, at the same time, they are digitized and transferred onto a PDP-11 computer for processing. A suit-able software package was developed to obtain different types of thermograms such as simple line profiles, 3-dimensional relief images and isothermal maps.

Rapid application of automotive brakes causes high temperatures with resulting thermal gradients. To analyze these components accurately, the inputs and heat transfer coefficients must be known. Transient thermal patterns measured on prototype parts were recorded on video tape using an infrared scanner. These temperature values were used as inputs for a finite element analysis to predict component stresses. This test series also showed that infrared thermography can be used to detect the development of thermal cracks in a component.

Recent improvements in thermal imaging systems having video recording and digital processing capabilities have resulted in renewed interest in thermography as a viable nondestructive evaluation technique. Examples of the use of real-time thermography for monitoring plastics manufacturing processes and structural integrity of fiber reinforced composites are presented. Newly developed passive thermographic and vibrothermographic techniques for characterization of composite materials are discussed.

Thermite is a mixture of a metal and oxide which is consolidated to form a composite chemical heat source. Thermal profiles of reacting thermite composites were generated and analyzed to determine the burn rate and the heat propagation during and after the reaction. These thermal profiles are used to establish rates of heat transfer. A time-expanded "infra-red thermography video will be used to show burn rate, heat propagation, and burn uniformity of consolidated thermite during reaction.

Heat powders are consolidated into dense composites to form concentrated chemical heat sources. During the reaction, a high temperature burn front propagates through the composites. The burn front is preceded by a lower temperature thermal front which generates thermal gradients. Thermography was used to determine thermal gradients preceding the burn front, during the reaction of the consolidated heat powder. The techniques involved along with the resulting thermography will be discussed.

A system has been developed under contract from the U. S. Air Force for noncontact testing of printed wiring assemblies (PWAs) in depot level environments. The testing is performed by sensing the thermal image of the powered PWA and comparing it to a thermal image from a known good PWA. Designed around a central host computer, the system is completely automatic and quite operator interactive. The complete system integrates a host computer with an Infrared Scanner, a Digital Image Processor, a trackball controller, a TV monitor, a video printer and a fixture for mounting the PWA under test.

Infrared thermometry has a long history of being used for high-temperature applications where no other conventional form of temperature measurement would prove effective or be safe. However, until recent years, instruments for precision measurements in the low tem-peratures were not available. Industrial leaders have been improving the accuracy and precision of infrared thermometers. Also the necessary size of the target has been minimized at good working distances. Sighting systems on the instruments have been improved so an end-user can identify the exact target being measured. With all of these improvements, a new generation of infrared thermometers has evolved. Complete system control and wide temperature range capabilities are now available.

Wormser Scientific Corporation has designed, provided construction surveillance, and performed testing on a large number of sizeable active solar energy systems over the past ten years. In solar energy systems, the energy or heat generated in individual solar collectors is transferred using a heat transfer fluid to a storage reservoir and from the storage reservoir to an industrial or institutional user. For best efficiency of operation, the system should be designed and adjusted to result in uniform temperature increase in the solar collectors when they are exposed to the sun and heat transfer fluid is circulated through the system. Since the author had previous experience with non-contact temperature measurement and scanning, he used these techniques in testing and adjusting the solar systems. The paper briefly describes typical large active solar energy systems and discusses methods of using remote infrared temperature sensors for testing and adjusting these systems.

Aerial thermography and spot radiometer techniques were used for the assessment of roofs and heat loss through building envelopes of office buildings. The inspections were part of the diagnostic programs developed by the National Bureau of Standards (NBS) for the General Services Administration (GSA) to evaluate the thermal integrity of new and existing office buildings. The infrared inspections by aerial thermography and the spot radiometer measurements were performed by outside contractors; all other tests in the program were performed by NBS. This paper presents the analysis and results reported by the contractors, and discusses the capabilities and limitations of equipment, and make recommendations for aerial thermography and spot radiometer inspections on office buildings. Also included are comparisons of R-values determined from spot radiometer and heat flow meter measurements, and discussions of the results in conjunction with the ground-based infrared survey and other techniques that were utilized. Specification formats for procurement of contractor services are suggested for further development.

Over the past few years, interest in the use of infrared thermography in residential dwellings has increased. With this growth comes the need for a better understanding of thermal images. Just as in other applications of thermal imaging, different thermal signatures represent different characteristics of the object being studied. Thermal signatures must be properly identified. In the case of residential thermog-raphy, thermal anomalies found on exterior and interior walls indicate certain conditions within the walls. images on interior walls can offer a great deal more information, if properly noted, than images on exterior walls. Through the incorporation of thermal imaging for quality control in residential insulation retrofit, a number of thermal patterns related to specific construction techniques have repeated them Selves. A majority of these patterns are common and quite recognizable. The purpose of this paper is to identify some of the common anomalies found in interior residential thermography, their relation to construction and their probable causes.

A data base of 3901 electrical problems discovered in industrial thermographic inspections is analyzed. Covering 165 days of field work, the data provide a basis for determining cost:benefit ratios. Analysis shows that an industrial plant can effect a $41,400/year savings by fully utilizing an inspection and repair procedure costing $2180.

Despite careful detailed planning of reinforced concrete structures, technical installations must subsequently be anchored in the concrete. The longer the time between the planning and completion of the structure, the greater is the expense and the more dependent the structure is on the further technical development of the installation. In power station construction, for example, one expects to have to install several hundred thousand anchorages for each station. The reinforcing rods should not be damaged during the necessary drilling work. Each damaged rod must be checked to ensure that the safe loadbearing properties of the structure are not impaired. A method which shows the exact position of the reinforcement in the concrete, considerably reduces the incidental and consequential costs of drilling work (Figure 1).

Thermography, used in construction engineering, has become a accepted tool in the last few years. In combination with new facilities (Instrumentation, application technologies) thermography not only is in use in energy saving, but also in quality controle and construction examination.

The increasing demand for thermographic process monitoring in industry can finally be met with the introduction of a new modular line-scanning technology that enables each individual user to fit an optimal combination of measurement and data-analysis functions to his requirements. This article describes some of its many applications andcompares the new line-scanning concept with existing temperature-measurement methods.