Inspectioneering Journal

Art to Science: Changing Infrared 180 Degrees

By Nagy Wassef, Technical Advisor at Quest Integrity. This article appears in the January/February 2024 issue of Inspectioneering Journal.


One of the hardest things in a marriage is getting couples to agree. Why is that? Simple, they each have their own opinion, and see situations through their own eyes. The same is true for infrared (IR) thermographers. It is unusual for two of them to agree on temperatures because they, too, see temperatures through their own eyes/instruments. Facts and opinions are different; although one spouse’s opinion is that the house is cold, the other spouse’s opinion could be that the house is hot. The fact is, however, the house is 72°F. Wouldn’t it be great if we could agree to agree? Wouldn’t it be great if we could distinguish facts from opinions in the world of infrared? The great news is now we can. We now have the ability to get repeatable, accurate, and reliable infrared temperatures for fired heaters. Not only that, but these values can be obtained by any trained infrared thermographer utilizing any fired heater applicable instrument.

It’s About Time... and Temperature!!

When asked why you trust your IR temperatures, the most common answer I hear from infrared thermographers (including myself in the past) is, “Based on my experience...” Well, assuming a brand-new infrared thermographer was hired who does not possess infrared experience, how would he know how to correct the temperatures if his boss is not able to share his experience? Maybe your reply is, “He will just send a preliminary report until his more experienced boss can confirm the temperature corrections.” In another scenario, if two different infrared thermographers have different experiences and techniques of correcting temperatures throughout their career, how would one infrared thermographer be able to prove his experience is more valuable than the other IR tech?

If these questions are making you second guess your experience, then you would surely agree that it’s important for us to continue developing and understanding infrared technology to keep up with this fast-paced tech world. Although experience is a valuable asset, we need to study the science behind our experience.

Is it true that there are ways to objectively correct infrared temperatures?

The main issue with conventional infrared technology is that it is subjective. Through the use of algorithms referenced herein using a scientific approach, one is able to achieve more accurate, objective results. The science was developed to make temperature corrections based on application models and theories presented by Dr. Peter Saunders [1]. These algorithms utilize a science-based infrared correction approach that is widely recognized and adopted [1]. Of course, in the digital age, the algorithms and any additional logic are best enabled by software that can be developed using the referenced science. The common temperature corrections utilized with conventional infrared monitoring are a single background temperature and emissivity. But as you can see, below, much more must be considered to achieve the levels of accuracy and objectivity needed. Table 1 shows the benefits and temperature corrections that the scientific algorithms must consider when correcting raw temperatures.

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