Every object whose surface temperature is above absolute zero (-273 degrees C.) radiates electromagnetic energy which is a function of its surface temperature. The intensity of this radiation varies along the wave lengths of the electromagnetic spectrum from visual to the infrared ranges.

This energy in the case of certain materials at elevated temper­atures falls in the longer wave length red end of the visible spectrum and may be seen (red hot steel, for example). As the wave length increases this heat generated electromagnetic energy moves into the infrared spectrum.

Using a highly sensitive, real time, infrared Imaging system it is possible to observe, quantify and record the thermal picture of the surface temperature of the object whose temperature is between -20 and +2000 degrees C. The sensitivity of the equipment is such that it is capable of detecting temperature differences between two given surfaces to an accuracy of 0.2 degree C. at an ambient temperature of 30 degrees C.

The infrared heat scanning equipment consists of an infrared camera, with optics transparent only to infrared radiation, and a TV type display monitor. The camera converts the radiated heat that it senses into an electrical signal. This signal is displayed on a special display monitor as a real time heat image of the object on which the camera is focused. The heat picture, known as a thermogram, is composed of a gray scale with continuous contrast ranging from black to white. Areas of higher temperature appear lighter, areas of lower temperature appear darker. If an object, or part of an object, is warm (or hot), it will appear bright in the heat image, if an object, or part of an object, is cool, it will appear dark in the heat image. Intermediate shades of gray indicate variations between the extremes of temperature.

The thermal image of an object shown on the display monitor screen can be photographed for a permanent record, using a specially adapted camera, and gives qualitative visual information about the surface temperature of the object.

Should quantitative temperature data be required the isotherm mode is selected on the monitor. To determine the temperature level of an object the isotherm marked is first set at known reference temperature body. The isotherm level is then varied throughout the temperature range until it reaches the area of interest (unknown temperature). The temperature differential between the known reference source and the object can now be determined from the information thus provided with the use of the system calibration curves.

Home