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Compensating for Reflected Temperature in Hot Environments
Tip provided by: Wayne Swirnow Infraspection Institute Staff Instructor

When performing quantitative thermography in areas with high ambient temperatures and strong, multiple sources of radiant energy, it is important to pay particular attention to the level and direction of the background energy reflected from objects being measured.

Both imaging and non-imaging radiometers convert the invisible infrared radiation emitted by an object into a temperature value. When measuring thermally opaque objects, the infrared energy collected by these devices is the sum total of energy emitted by, and reflected from, the target’s surface. When performing infrared inspections in areas with significant sources of reflections, it is important to understand and control sources of reflected energy to help eliminate both qualitative and quantitative errors.

An example of an environment with significant background radiation would be the emergency generator room of a data center. Often this is a small room populated by one or more large diesel engines with attached generators. These engines have exposed high temperature exhaust manifolds and pipes, turbo chargers, and coolant pipes all of which radiate large amounts of heat during operation. The thermal reflections created by such equipment can make qualitative imaging difficult and significantly affect the accuracy of radiometric temperature measurements.

Emergency generators are often located in close proximity to electrical switchgear and transfer switches which are the subject of an infrared inspection. When performing an infrared inspections in such locations, thermographers can minimize errors by shielding the measured object from sources of reflections. In some cases, a thermographer may use their own body to help shade or shield the target. As an alternative, it may be necessary to use a sheet of cardboard or other thermally opaque material to temporarily block the source of the reflected energy.

When using a radiometer that has corrective inputs for reflected energy, a thermographer should measure and compensate for reflected temperature to further ensure measurement accuracy.

The Infraspection Institute Standard for Measuring and Compensating for Reflected Temperature Using Infrared Imaging Radiometers provides simple and practical procedures for dealing with errors associated with reflected temperature. Copies of the standard are available through the Infraspection Institute Online Store .

Wayne Swirnow is a Level III Infraspection Institute Certified Infrared Thermographer® and professional infrared consultant. Wayne specializes in commercial and industrial thermography as well as being certified by the Building Performance Institute as a Building Analyst. Wayne is the founder and owner of Infrared Imaging Services LLC a commercial infrared inspection company, headquartered in New City, NY.

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