Thermal Imaging Blog from Fluke Thermography

I’ve been working on a project this past week with a couple of young people. I’m impressed with two things. First, they have more energy than I have. Second, I have more experience than they have. While energy is great, relying on experience often means I know how to do things “smarter,” using less energy. I know I sound like an old guy now (and I am) but it also causes me to remember how much I’ve learned from so many other people over the years. For that I am grateful!

Last week we talked about how important mastery of the basics is. If you haven’t mastered operation of your imager or the basics of heat transfer, get out a calendar and commit yourself to a plan to do so.

I also recommend keeping a list of questions you encounter. Jot them down in a notebook or on your computer. Questions like, “Why do the reflections of the ducks appear warmer than the ducks themselves?” (See below for a discussion.) Or one of my all-time favorites, “Can we see an infrared rainbow?” (Short answer: yes, but not with the technology you and I can afford!) There will be, of course, hundreds of seemingly more relevant questions to be listed and answered.

Some of the best questions are “dumb” questions, those asked in innocence or ignorance! Don’t be embarrassed by dumb questions—unless those are all you ever ask!—but embrace and learn from them. There are also many useful questions to which there are no ready answers; these cause us to stretch and seek and, I find, often lead us to new and important places.

Students in our training courses often remind us how important hands-on discovery is in the learning process. They don’t want to hear us lecture, they want to explore and discuss with others. Learning doesn’t get any better than hashing things out with each other!

I often find setting up a simple experiment with a friend can help us understand an unknown issue or answer a question. Together we can provide a valuable “check and balance” for each other and test our knowledge in several ways. At that point we can also validate it against what others have learned. If it still passes the test, only then can we cautiously accept it as a working hypothesis.

If you are going to grow in this profession, you’ll need to become an expert. Don’t duck away from what you don’t know. Dive into it and learn! And by all means explore and learn with your professional colleagues—they too will have a long list of great, dumb questions.

Why do the reflections of the ducks appear warmer than the ducks themselves?

• Radiance from just water = emission from water + reflection from clear (cold) sky
• Radiance from duck reflection = emission from water + reflection from clear (cold) sky + reflection from side of duck.
• Radiance from topside of duck = emission from (wet) duck + reflection from cold sky.
• Radiance from side of duck = emission from duck + reflection from water
• Duck reflection = reflection of emitting/reflecting duck + reflection of sky + emission of water

So…if the topside of the duck is cooler than the water, then the reflection should appear warmer than both the water and the topside of the duck.

Adding the duck’s reflection to the water’s emission/reflection makes it appear slightly warmer than all else.

Thinking Thermally,
John Snell—The Snell Group, a Fluke Thermal Imaging Blog content partner Normal 0 false false false EN-US X-NONE X-NONE

Normal 0 false false false false EN-US X-NONE X-NONE

I’ve been working on a project this past week with a couple of young people. I’m impressed with two things. First, they have more energy than I have. Second, I have more experience than they have. While energy is great, relying on experience often means I know how to do things “smarter,” using less energy. I know I sound like an old guy now (and I am) but it also causes me to remember how much I’ve learned from so many other people over the years. For that I am grateful!

Last week we talked about how important mastery of the basics is. If you haven’t mastered operation of your imager or the basics of heat transfer, get out a calendar and commit yourself to a plan to do so.

I also recommend keeping a list of questions you encounter. Jot them down in a notebook or on your computer. Questions like, “Why do the reflections of the ducks appear warmer than the ducks themselves?” (See below for a discussion.) Or one of my all-time favorites, “Can we see an infrared rainbow?” (Short answer: yes, but not with the technology you and I can afford!) There will be, of course, hundreds of seemingly more relevant questions to be listed and answered.

Some of the best questions are “dumb” questions, those asked in innocence or ignorance! Don’t be embarrassed by dumb questions—unless those are all you ever ask!—but embrace and learn from them. There are also many useful questions to which there are no ready answers; these cause us to stretch and seek and, I find, often lead us to new and important places.

Students in our training courses often remind us how important hands-on discovery is in the learning process. They don’t want to hear us lecture, they want to explore and discuss with others. Learning doesn’t get any better than hashing things out with each other!

I often find setting up a simple experiment with a friend can help us understand an unknown issue or answer a question. Together we can provide a valuable “check and balance” for each other and test our knowledge in several ways. At that point we can also validate it against what others have learned. If it still passes the test, only then can we cautiously accept it as a working hypothesis.

If you are going to grow in this profession, you’ll need to become an expert. Don’t duck away from what you don’t know. Dive into it and learn! And by all means explore and learn with your professional colleagues—they too will have a long list of great, dumb questions.

Thinking Thermally,

John Snell—The Snell Group, a Fluke Thermal Imaging Blog content partner

Some problems don’t necessarily “shout” at you. The increase in temperature of this surge protection device in a substation is only a few degrees warmer than normal. Seeing the signature required adjusting the imager skillfully. Understanding the device could fail at any moment required additional background knowledge and clear communication with the customer.

Nothing is so important in this business as knowing the basics. That’s why I’ve often come back to such topics as adjusting level and span or emissivity or heat transfer. You can have a great imager, good training and a picture-perfect report, but if you don’t have the basics down pat, you’ll never succeed in making a difference for your customer—and making that difference is the only way to pay the bills!

Thermographers can learn a great deal, and test their skills, by simply looking at the world around them and questioning what they see. For example, why do the reflections of the ducks in the water appear warmer than the ducks themselves? While we may not care about ducks, the thought process will help make us better themographers. More on this next week!

In the 30+ years I’ve been in this business I’ve seen many people try to cut corners to get going faster. In the end they always make mistakes, sometimes serious ones, and have to go back to get the basics right.

If you don’t fully understand every last feature of your imaging system, take some time over the next few days or weeks to do that. Even if you don’t routinely use a certain feature, learn how it works so you have it in your “tool kit” when you do need it.

Make sure your images are perfect– perfect focus, perfect perspective, and perfect level/span adjustments. Why would you settle for anything less?

Determine how you will incorporate radiometric temperature measurements into your work flow. There is no right way, but take the time to state it clearly so your customers understand what you are doing and why. Then follow your procedure.

Are you still feeling a bit fuzzy about some part of heat transfer and radiometric theory? Dive back into your training manual and/or take a webinar or class so you are 100% clear about it. I still find each time I go back to the basics I learn something new and reinforce what I already know.

Reports are an essential part of our work. The professional standards I mentioned last week give good guidance on what that report should look like, at a minimum. Manufacturers like Fluke have done a superb job of developing report writing software that not only makes life simple but also produces great looking reports.

A thermographer can find few tasks as important, or rewarding, as reviewing the report with the customers. It is the best way to ensure corrective action is taken in an effective way and to determine the best measure of success.

The report, a great a product as it may be, is usually not our end product. It is just one of the steps along the way to having our work actually make a difference. The steps to success are not magic. They include (1) establishing good communications with the customer, (2) conducting a thorough and professional inspection with the most appropriate imaging equipment, (3) documenting our work and, finally and most importantly, (4) following up with the customer.

While our role in having work actually accomplished may be limited, I’ve often found going over the report with the customer provides a great opportunity to “close” with them and secure a promise of action on their part. On a practical level, customers often have questions, either technical questions or questions about the interpretation of our findings. Without answers, the whole process can get stalled and end up in a pile on their desk.

Finding a problem like these hot connectors on a dry transformer means the customer can avoid a very costly failure—if they actually are motivated to fix the problem beforehand. The thermographer’s role should include a follow-up after the inspection and the report to ensure successful completion of the work.

I remember a great thermographer at an auto plant who printed all of his reports with a highlighter-yellow border on them. When he walked around the plant, he could quickly spot his reports and immediately follow-up with his customers. His intention was not just to create a fancy report but to have that report motivate the customer to do the work to correct the problem. His simple system allowed him to get much better results than many others in his company.

I had a great example of the value of a follow-up with an insulation contractor. For whatever reason he could not make sense of the images in my report. He kept drilling in the wrong places and not finding what I said would (or would not!) be there. By the time I stopped by the job site, he was so frustrated and so sure I was wrong, he’d “blown me off.” When I showed him how to read the images—both understanding the color palette and being able to locate the problem areas—all was well and the job was completed successfully. I also made a friend and ally of him for future work.

The last contact we have with the customer should not be just sending out the report (or the invoice). We are successful only when our work makes a difference. Why? The savings in the long run, quite literally, pay our salaries! If the work is not done, we’ll end up out of a job. The best way to measure our performance is to see how often our work motivates the customer to get the job done. So pick up the phone or stop by their office and see how things are going. In the end, if you are doing your job well, they may also, as I discovered, give you more work or even a referral. Not bad for a day’s work!

Thinking Thermally,

John Snell—The Snell Group, a Fluke Thermal Imaging Blog content partner

Last week I talked about the value of following professional standards. Not only do they lay out the best “recipe” for success but standards are also widely accepted as “collateral” in most industries where we work. By following standards, your work will immediately gain credibility.

Section 14 of ASTM C-1153, Standard Practice for Location of Wet Insulation in Roofing Systems Using Infrared Imaging, clearly states what data needs to be collected and included in the report if the work is to comply with this important professional document.

A key component of all standards is documentation. Not only do the images need to be documented, but the data about the conditions before and during the work. In order to make your life simple and your work effective, I urge you to make data collection as systematic as possible. There are few things worse than scrambled or missing data but some of us had to learn that fact the hard way! Please learn from my mistakes.

Nearly all standards have a list of data that should be recorded for the entire job. Such things as air temperature, wind speed and direction, building type, time of day/night, etc. are all captured for the entire inspection. Of course, if there is any change during the inspection, that should be noted. The check list you work from for your inspection should key directly to the standard you are following.

With regard to the inspection itself, more data needs to be collected for each and every image. Many new thermal images make this documentation very easy by providing both a simultaneous visual image and either text or voice annotation. While the visual image may not always be perfect(due to poor lighting, lack of detail, etc) it is typically good enough to provide basic identification information later should any questions arise. Gone are the days of matching up separate visual and thermal images! Still, when faced with abnormally bright or dark scenes, take the time to make sure the visual image is adequate.

Fluke’s new IR-PhotoNotes system provides another brilliant means of documentation by linking associated images. You can, for example, take a visual image of the identification numbers on the front of an electrical enclosure and associate it with the thermal image of what is inside. I predict you’ll find this feature very useful!

I find the voice annotation feature to be very useful. I like to script what I’m going to say so that I know I’ve gotten all the details in the proper order when I listen to them while writing the report. For example, in a building I’ll clearly state (1) floor level, (2) direction of view, (3) exterior or interior wall, and (4) a quick description of what I’m seeing. If I’m in a motor control center (MCC), I might state (1) equipment identification numbers, (2) type of device, (3) phase and line/load side on which the problem is found, (4) load across the phases and again, (5) a quick description of what I’m seeing.

One bushing on an oil-filled circuit breaker can look just like another one after a long day’s work. Good documentation is critical to success. You don’t want to point the repair crews to the wrong bushing or have them miss this one that may well be ready to cause an outage.

Text annotation, whether in the imager or in the report template, should be keyed to the voice annotation so that you can listen to your voice and quickly fill in the related text. That, in turn, should show up directly in the merged report. What a time savings that all can be!

Take the time to streamline the data you record. Get what you need and do it in a systematic fashion. The investment will pay handsome returns when it comes time to write your report,do your analysis, and again when you sit down with the customer to explain your work.

Thinking Thermally,

John Snell—The Snell Group, a Fluke Thermal Imaging Blog content partner

Last week I talked about how to move yourself and your imager into the best position to get good thermal data. Another big part of being successful is understanding and following professional thermography standards. Like a good time-tested recipe, these help us get high quality, consistent results.

As I’ve said before, I’ve made plenty of mistakes in the nearly 30 years I’ve been in this business. In fact the knowledge many of us gained in making mistakes is the foundation for professional standards. Following standards helps us avoid common mistakes and follow procedures that will result in success.

Inspection of buildings, especially large ones, needs to be done following professional standards.

Thermography standards have been developed under the auspices of two primary organizations, ASTM and ISO. Additionally, the National Fire Protection Association (NFPA) has two standards that relate to the technology. Other organizations have also developed standards related to thermography and more are being developed every year.

All professional standards are written and kept current by volunteers in committees. All are also copyrighted and can be purchased for a reasonable fee. Revenue from selling standards is a primary source of support for the activities of the organizations, so I would ask that you purchase standards rather than use illegal copies.

Currently excellent standards exist for all the main applications of thermography. This is what is available:

• ASTM E 1934, Standard guide for examining electrical and mechanical equipment with infrared thermography

• ASTM C-1060 Standard practice for Thermographic Inspection of insulation Installations in Envelope Cavities of Frame Buildings

• ASTM E1186 Air Leakage Site Detection in Building Envelopes and Air Barrier Systems

• ASTM C 1153 Standard Practice for the Location of Wet Insulation in Roofing Systems Using Infrared Imaging

• ASTM E2582 Infrared Flash Thermography of Composite Panels and Repair Patches Used in Aerospace Applications

• ISO 6781 Thermal insulation, qualitative detection of thermal irregularities in building envelopes, Infrared Method

• ISO 18434-2.1 Condition monitoring and diagnostics of machines—Thermography —Part 1:General procedures

• ISO 18436-7 Condition monitoring and diagnostics of machines — Requirements for qualification and assessment of personnel —Part 7:Thermography

• NFPA 70-B, Recommended practice for electrical equipment maintenance

• NFPA 70-E, Standard for Electrical Safety Requirements for Employee Workplaces

Where would building professionals be, for example, without standards relating to the use of the blower door? The same need for standard methodologies apply to using a blower door and a thermal imager.

In addition to these there are also standards for certification as well as a number of standards related to the imagers and infrared radiometers we use.

To be honest, a number of these standards need to be updated and there are more areas of application where work needs to be done! All of the professional committees responsible for these standards are driven by volunteers like you and me. The work is not hard but, in our ever busier and busier world, many feel they have less and less time for such things. We all will pay for this neglect!

I urge you to obtain and use professional standards. That will benefit us all. I also ask that you consider volunteering on the committees that write and maintain standards. If you’d like more details, just go their respective websites and initiate contact with them.

Thinking Thermally,

John Snell—The Snell Group, a Fluke Thermal Imaging Blog content partner

After years of working with new thermographers in our training classes, I’ve learned a lot about how people learn. First, we never get it right the first time! Don’t worry about making mistakes, in fact, it is important to make them. But it is also equally important to learn from them. In class we let people “stumble” once or twice but we help them find where the learning “trip hazards” are and protect them from major failures.

A very common mistake new thermographers make is to stand in one position. Not surprising! They get so fascinated with their new “toy” that they forget to even move. Moving, but doing so safely, is crucial to getting good results.

It is important to move to a position that you capture some point of reference in the image. In this case we can see all three phases and quickly see it is the center phase that has a heating problem.

Whether we are searching for an anomaly or trying to get a detailed image of one we’ve already found, it is important to be in the right place. When searching, plan to move a lot. Get in a spot with a good vantage point and scan over large areas using appropriate level and span settings, usually set manually (Learn more about setting level and span manually here). Avoid walking and looking at your screen at the same time. To do otherwise is just asking for an accident. Move, stop and image.

If you are detailing something you’ve already found, whether a hot electrical connection or an area of missing insulation, get as close as you can safely to show exactly the area you want to document. Typically for an electrical connection, this means showing at least two of the three phases, and preferably all three at once. For insulation or air leakage, show the problem and an easily recognized object, like a door or window, to help locate where you are looking. In all cases, move closer. Every pixel in our image is important and the closer we are the more value they have.

While either image can work, the one on the right is better because it is taken at right angles to the wall and, as a result, is in better focus.

I’ve also watched new thermographers struggle with focus. Often this is because they are simply in the wrong place. In a building, for instance, they often try imaging a long wall from one spot with the result being part of the wall is out of focus. Remember modern imaging systems have a very shallow depth of field. It is far better to move and stay parallel to the wall and take several images, all of which you can easily keep in focus. The same thing happens when looking at an overhead buss duct. Focus, image, move and repeat.

Remember that like visible light, infrared radiation travels in a straight line. We need to get in a position that we can see the “target” with our eyes before we have any chance of seeing its thermal image. Once you get the basics of camera operation down pat, you can more easily think about where you need to be to get those great images. But when you move, do it safely. Watch for trip hazards and moving vehicles and don’t move and view the image at the same time.

Next week I’d like to return to the topic of industry standards. We don’t need to re-invent our profession. We just need to be smart enough to follow the “recipes” others have developed for us.

Thinking Thermally,

John Snell—The Snell Group, a Fluke Thermal Imaging Blog content partner

Last week we discussed how to adjust level and span manually. Sometimes this can lead to a lot of “button pushing!” It is not a big deal – just one of life’s little aggravations. Thankfully, many models of Fluke imagers have a very helpful solution: 1-TIME AUTO ADJUST.

Both images were taken using AUTO adjust. In both cases the overall image quality is excellent but there is not a great detail in the hot/cold water itself. Why? The temperature of the counter on which the cups rest determines one end of the SPAN setting.

How does 1-TIME AUTO ADJUST work?

When the imager is in the MANUAL mode, you can press the F3 button and instantly get a 1-TIME AUTO ADJUST. This feature works just like AUTO but with one very important difference: it only works when you press the F3 button. The image is then adjusted based on whatever is in the field of view at that moment. The warmest temperature defines the upper limit of the SPAN and the lowest temperature defines the lower limit.

Using the same cups, I simply moved close enough to the water to exclude the counter from the field of view and pressed F3 (1-TIME AUTO ADJUST). Immediately the SPAN is decreased and the LEVEL set appropriately for each cup to give amazing detail in the water (and ice).

When does 1-TIME AUTO ADJUST work best?

As I indicated last week, I often find it most useful to be in the MANUAL adjust mode. But it is also great to have the option of quickly re-adjusting the SPAN. When?

• If I need to quickly adjust to the right SPAN and LEVEL to look at wall insulation, I will walk right up to the wall and press F3. The image immediate adjusts a very tight SPAN at a LEVEL appropriate to the wall temperatures.

• When I don’t understand how to best adjust an image for a particular situation, for example an energized dry transformer, I can press F3 and quickly get a different view; it may not be perfect but it will help me understand what further manual adjustments I need to make to get a perfect image.

• When I’m conducting a functionality check of my imager by viewing the face of a person, I can move close to their face, press F3 and quickly end up with an image adjusted with a narrow SPAN for a LEVEL appropriate to facial temperatures, just as I did with the wall.

Inside a home the sun on the window shade is hot enough to force the SPAN setting to be increased so much that the spot of missing insulation is not easily seen. The solution? I moved close to the wall, excluding the window, and pressed F3 (1-TIME AUTO ADJUST), allowing me to see the insulation issue. The overall image is “noisy” due to the narrow SPAN and the window is now saturated but the detail I want for my analysis is much more clear.

What are the limitations of 1-TIME AUTO ADJUST?

Just as is the case with using AUTO, if you have extraneous hot or cold areas in the image, 1-TIME AUTO ADJUST will take them into account as it adjusts, resulting in a poor quality image.

How can I use 1-TIME AUTO ADJUST successfully?

Ensure that objects with extraneous hot and cold temperatures are not in the image when you press F3. As an example, rather than pressing F3 while viewing a wall with a cold window and warm radiator, point the imager at the floor or move closer to the wall so you are viewing only the wall. When you then press F3, you’ll get an adjustment that is much closer to what you want.

Of course you can always make a fine adjustment by going into MANUAL or, after downloading the image in Smartview. If you have it, try 1-TIME AUTO ADJUST and learn what it can and cannot do. You’ll quickly learn when to use it to great advantage.

Next week we’ll move on to the basic, but very important topic of what is your point of view. This will not be a political discussion, but one of how to gain the best thermal image!

Thinking Thermally,

John Snell—The Snell Group, a Fluke Thermal Imaging Blog content partner

Last week we discussed how to adjust level and span automatically and when that feature is best used. While using AUTO can be very convenient in many situations, you’ll quickly find times when MANUAL adjustment is essential, either to getting the best image or understanding what you are seeing.

Use AUTO adjust to get “in the ballpark. The problem is, when you have a large span of temperatures—cold to hot in the case—there is little detail in any single cup.

How does MANUAL work?

Although it takes a bit of button pushing to get there, using MANUAL adjustment is not difficult and you’ll quickly learn how to do it without thinking. The current mode you are using is displayed in the upper right corner.

Many models of Fluke imagers are have a great feature designating the F1 key, when held down for several seconds, to toggle between AUTO and MANUAL modes. You can also quickly get to MANUAL by pressing the F2 key until the menu choices show MANUAL or AUTO. Either way, just press the F2 key again or until you reach the options for LEVEL or SPAN and then INCREASE or DECREASE.

I find it easiest to adjust SPAN first to what I think will be most useful.

When does MANUAL work best?

• I use the MANUAL feature when I know I’ll need a very narrow span. For example, if I want to trace down the location of heating in an electrical component, I’ll set the SPAN at a minimum and then increase LEVEL until only a small visible area is left in the image.

• If I have a good idea of what the difference temperature should be, say between insulated and uninsulated areas, I can adjust the SPAN to that difference and adjust LEVEL to the temperature of the insulated wall; the uninsulated areas will then show as warmer or colder depending on the direction of heat transfer.

• Whenever I’m looking at a situation where temperatures are changing, such as a steam trap cycling, and I want to determine exactly when they reach a certain level, I can fix both SPAN and LEVEL manually and watch for the object or process to show up.

• If there are extraneous objects in the field of view that will cause the AUTO function to adjust poorly, I can adjust manually exactly as I’d like the image to be.

When I use MANUAL mode, I can adjust SPAN to be quite narrow and LEVEL appropriate to each cup individually. The result is amazing detail in each cup.

What are the limitations of using MANUAL?

Using the MANUAL adjustment mode is not as fast as AUTO. I guarantee you will get tired of pushing buttons on some jobs! There will also be times when you’ve adjusted the image so that you can understand what you are seeing but, overall, the image will not be very good looking or even understandable to a non-thermographer. In such cases two images may well be needed, one adjusted manually showing the exact problem and another adjusted more broadly, either manually or automatically, showing the problem in the overall context.

SPAN and LEVEL adjusted appropriately for this cup.

How can I use MANUAL successfully?

All thermographers must master using MANUAL adjustments or they end up missing a great deal. There is simply no way around it. Practice on the same three cups of water I talked about last week. Interestingly, you will find that the best MANUAL adjustments are often very similar to what you achieved with AUTO when you moved in close and excluded extraneous objects. Remember, if the MANUAL adjustments are not working for you, just switch briefly back to AUTO to see what is going on or drop the image into Smartview and optimize the settings there.

SPAN and LEVEL adjusted appropriately for this cup.

Next week we’ll talk about a really great feature available on many Fluke imagers, 1-time auto adjust.

Thinking Thermally,

John Snell—The Snell Group, a Fluke Thermal Imaging Blog content partner

We want to know how Fluke thermal imagers have helped you, and to say thank you, we are giving away a brand new 55 inch flat screen TV!  Tell us how you have been able to:

• Grow your business
• Spot inefficiencies
• Reduce costs
• Improve your productivity

Tell us your story; include situations and discoveries made with your Fluke thermal imager. Don’t worry, you don’t have to write a full essay – give us some general comments, we’ll conduct a phone interview, write it up and submit it to you for your final approval prior to publication.

For more information and to enter to win, visit here.

55" Samsung flat panel LED 6005 Series Smart TV (a $1249.99 value)

I’m all for using the AUTO adjust feature found on most thermal imagers. That said, it does not mean I can turn my brain off! Many new thermographers believe they can just put their system on AUTO and life will be good. Not true.

AUTO adjusts the span of the image to accommodate all three cups by setting the top of the SPAN at 130F and the bottom at 30F.

How does AUTO work?

The AUTO feature is brilliant. It analyzes the image and adjusts to whatever is in it. The highest and lowest radiance levels define the top and bottom of the span setting, as well as the level of mid-point.

You can easily see AUTO in action by looking at three cups of water, one hot, one cold and one at room temperature. Notice what happens when you view all three in one image. Now watch the scale change as you isolate each cup individually. I would encourage you to practice until you are clear how AUTO works and what the limitations are.

When each cup is imaged individually, AUTO changes the span setting based on which cup is in the image. For the cold cup (left) span become 29F-70F, for the room temperature cup (middle) span becomes 64F-77F and for the hot cup (right) span becomes 64F-128F. Not my warm reflection in the center cup driving the upper limit of the span up slightly.

When does AUTO work best?

• I use the AUTO feature when I have little idea of what my setting should be. AUTO will generally get me in the ballpark, hopefully at least to have a decent image and a basic understanding of what’s going on.

• I also use AUTO when I’m looking at a wide variety of new territory, whether that is a building or a manufacturing facility. Again, my intent is to have a basic image (even if the temperature range is not refined) that gets me to the next logical step.

• When I’m looking at something that is changing temperatures fairly quickly, like a radiator heating up or fluid being transferred after a valve is opened, AUTO can change settings much faster than I can manually. This allows me to see the changes and understand them.

What are the limitations of using AUTO?

If there are any extraneous hot or cold objects in the image, they will cause AUTO to adjust and accommodate these extremes. For example, if you look at a hot line connection with the clear sky behind them, the lower end of the scale will probably be set at -20F or lower and the connector will not appear hot. Or in a house, if you have an incandescent bulb and a window in the image, the insulation patterns in the wall will be lost because the span is set too wide.

How can I use AUTO successfully?

Keep extraneous hot/cold objects out of the image when possible. Use AUTO as a starting point and, as needed, switch to MANUAL (I’ll cover this next week) or drop the image into Smartview and optimize the settings there. AUTO works well as long as you use it as a tool and not simply rely on it for an answer!

Thinking Thermally,

John Snell—The Snell Group, a Fluke Thermal Imaging Blog content partner

The image palettes we have available to us are remarkable. They’ve come so far since I first got into this business in 1983. We can now also easily change the palette in the software. Wow!

The Fluke AMBER palette with red and blue saturation indicators is a nearly perfect palette to use, especially in the field while working. The blue saturation shows air leakage into the ceiling in the left section of the roof. The blue rectangles are cold windows and a cold metal chimney flue

Still, many people have questions about which palette to use. My recommendations are as follows:

• While working in the field I strongly recommend using a “monochromatic” palette. Fluke has really perfected the AMBER palette, which  incorporates red and blue saturation indicators. You can’t go wrong working in this palette day in and day out! My second choice is the GRAYSCALE but it is not as good as AMBER. RED-BLUE can work well in the field, but it tends to not print well in a report.

• For reports I often use the HIGH-CONTRAST palette because it looks so darned good in print! Be aware that sometimes it can be confusing to non-thermographers—even when they are  nodding their heads saying “yes, I see…”—so make sure the imagery is clear and simple. And watch out for the green tones as they are not very intuitive.

The HIGH-CONTRAST palette can work very well in reports as people find the images very persuasive. The performance of three different windows can be seen very clearly in this winter image. The top window is single-glazed, the bottom right is double-glazed and the bottom left is a high-performance, low-E double-glazed window.

• Don’t routinely use either of the inverted palettes (AMBER or GRAYSCALE) because they are not the norm. However, every once in a while I find them very useful, especially to show small hot spots. If you use an inverted palette, clearly indicate the same to minimize the chance of confusion.

I see many new thermographers continually switch through all the available palettes. This is a waste of time. Consider my recommendation, try them for yourself, and learn which ones work best and stick with them. If you ever do have a doubt, and some scenes are challenging to portray, simply drop the image into Smartview and change it though all the options. You’ll quickly see which one works best.

Thinking Thermally,

John Snell—The Snell Group, a Fluke Thermal Imaging Blog content partner

When Fluke IR-fusion® was first launched, I wondered whether or not it would be perceived as just another marketing gimmick, and if not, how well it would be used. Time has proven that few find it gimmicky and most use it very well.

In the field I nearly always use the Full Infrared setting (left) for IR-Fusion® rather than the Picture-in-picture setting (right) which results in a smaller version of the thermal image. The blue area is where air is leaking into the kitchen exhaust fan ductwork.

Over the years, I’ve learned a couple tricks about IR-fusion® that I wanted to pass along. First, while in the field I nearly always use the Full Infrared setting. Remember, no matter how the image is set up I can change it later in Smartview, given that I’ve saved the images in an IS2 format, to whatever I want.

I see many people use the Picture-in-picture setting while in the field, but I don’t recommend it. Why? I want to use every bit of the screen to display the vital thermal information rather than just seeing a small portion of the center of the screen.

I also see many new thermographers using the Blended setting in the field. Again, I do not generally recommend this. Not only do we want a full infrared image, but we don’t want to make a mistake common to using the blended setting. Experienced thermographers know glass is opaque, but the blended setting has caused many new thermographers to assume they are seeing through a window.

Once I’ve imported the image file into Smartview, I switch the setting as appropriate. For reports, I’m a big fan of both the Picture-in-picture setting, as well as the Blended settings, because they so powerfully show the relationships between the visual and thermal worlds.

And don’t forget this important fact: when your IR image is in focus, the alignment of the thermal and visual images in IR-fusion® is perfect. No imager manufacturer other than Fluke can say that and it is worth a lot!

Take some time this week and explore how the various IR-fusion® setting work and which are best at showing the information you want. And please let us know what you think in the comments section so others can learn from your experiences!

Thinking Thermally,

John Snell—The Snell Group, a Fluke Thermal Imaging Blog content partner

We’ve spent the past several weeks discussing heat transfer. Radiation is a special mode of transfer because that is the mode by which energy is transferred from surfaces to our imagers.

All of what we see in the thermal image is nearly always based on the amount of radiation emitted from or reflected by the surface. Most of the time, it is quite easy to distinguish strong or specular reflections because, like a mirror, they move when we move – relative to the surface.

Applying a piece of electrical tape to either a cold window glass (top) or a warm sheet of steel (bottom) with variable oxidation allows a thermographer to consistently make accurate radiometric temperature measurements. Note both materials are quite reflective. In both cases the emissivity is set for the value of the tape (0.95) with an appropriate reflected background correction value.

But we are often interested in measuring the temperatures of the objects we are viewing. When we measure radiometric temperatures, we are really only carefully quantifying the radiation that makes up the thermal image. The imagers are calibrated to correlate a temperature with a certain level of radiation intensity. If a surface emitted perfectly, we could easily know its temperature based on how much radiation it emitted. The hotter it is, the more it radiates. But no surface emits perfectly!

From opaque (non-transparent) surfaces we see a combination of emitted and reflected. Because the reflected radiation is not related to the surface temperature, we must tell the imager to disregard that portion of what it sees. We do that by correcting for emissivity (E); reflection (R) then is 1-E.  We must also correct for the temperature being reflected. With these two pieces of correction information, the imager’s processor can determine an accurate radiometric temperature.

The correction, however, is not as accurate as we’d like it to be when the surface has an emissivity of less than 0.6 (approximately) or when the reflected temperature is extremely different that the surface temperature. This is true of all imaging systems especially when they are used in the real world versus a laboratory where all variables can be controlled. Clearly the proviso about emissivity means you cannot measure temperatures of nearly all bare metals—a fact that is, unfortunately, not widely reported in our industry.

When you need a high level of accuracy, especially on low emissivity surfaces, and where safety allows, simply apply a small piece of electrician’s tape firmly to the surface. Set the emissivity to 0.95 and the background correction to the temperature of whatever would be reflected if the tape were a mirror. You should be able to achieve an accuracy of +/-2C or 2% of the measurement.

I would urge you to try some simple experiments in the quiet of your office or kitchen until you are comfortable making the corrections and achieving a high level of accuracy.

Try and it out and let us know how it goes in the comments section.

Technorati Code: S2PFW5XB9AU4

Thinking Thermally,

John Snell—The Snell Group, a Fluke Thermal Imaging Blog content partner

For young children and pets, the first look in a mirror can be very confusing! They may be asking themselves. “Is that real or…?” Most thermographers share a similar exasperation the first time they see a thermal reflection, most commonly from a bright piece of metal. Many go on to understand that reflections are not reality, but many also continue to be confused about exactly how to deal with them.

All surfaces are reflective to infrared radiation to some extent. Bright metals are the most reflective. You can feel this by moving a piece of common aluminum foil very close to your face. Suddenly your face will feel warm! Why? The foil reflects your body heat back on itself rather than having your body radiate to cooler surroundings.

Most surfaces are not particularly reflective. Human skin is among the least so, but even we—regardless of skin color—are about 2% reflective. Most painted or heavily oxidized surfaces are between 10-20% reflective.

Window glass is somewhat reflective to infrared radiation and, more importantly, highly specular or mirror-like.

Glass and still water are two common surfaces that are very thermally curious. While they are only 20% and 5% reflective, respectively, because they are very smooth they can look mirror-like or specular. When polished smooth, any materials  like stone, tile, wood or even glossy paint, will appear specular even though they many not be highly reflective.

There are two easy ways to understand how reflective a surface is. First, while looking through your imager, simply move back and forth. If what you see changes appreciably, the surface is probably fairly reflective or specular. Next, heat the surface 10-20F above ambient temperature and firmly apply a piece of electrician’s tape to it. If the tape shows up clearly, the material is probably fairly reflective. Try this!

For all materials not transparent to infrared radiation—and fortunately that means most materials—reflection and absorption have an inverse relationship. Human skin  is both 2% reflective and 98% absorbing. Bright aluminum is approximately 95% reflective and only 5% absorbing.

Over the course of the next week, have some fun exploring which materials are reflective and which are not so reflective. See what you can learn. We’ll come back next week and discuss the issue of emissivity, in particular how understanding it is essential to making an accurate radiometric temperature measurement.

Thinking Thermally,

John Snell—The Snell Group, a Fluke Thermal Imaging Blog content partner

For the past several weeks, we’ve been reviewing heat transfer. Thermographers must understand the basics if they are to successfully interpret their images. Over the next two weeks, we’ll wrap up the review with a discussion of radiation.

Electromagnetic radiation is not only a powerful mode of heat transfer, it is also the way energy moves from a surface to the detector of our imaging systems. We already know a great deal about many forms of radiation. Electromagnetic radiation travels at the speed of light, in a straight line and can most easily be defined—even if not completely accurately—as a “wave.”

Radiation is defined by its wavelength. We define various “bands” of wavelengths, such as ultraviolet, visible light, and long-wave infrared, based mainly on how they interact with materials. While each band or form differs in significant ways, some also share commonalities. Some materials are transparent to certain forms, like light passing through a glass window. Look in a mirror and you are seeing electromagnetic energy being reflected. Sit outside on a sunny day or next to a fire and your skin absorbs radiant energy making you feel warm.

My wife, sitting by the fireplace, enjoys the fact that infrared radiation is strongly absorbed by human skin.

When infrared radiation interacts with materials, interesting things also happen. Thin-film plastic, regardless of color, is quite transparent. Most bare metals, even if somewhat oxidized, are fairly reflective. And nearly all non-metallic surfaces absorb infrared radiation efficiently—no matter what their color.

For thermographers, the sun is typically the most critical source of radiation affecting our work. Sunlight is composed of a full spectrum of radiant energy rather than just light or infrared so it can behave uniquely. Outside, its energy is quickly absorbed causing surfaces to heat various degrees (no pun intended). We need to pay attention to the color of the surface because absorption of full-spectrum sunshine, unlike infrared radiation, does vary with color. A brown ceramic insulator in a group of gray polymer insulators will often be warmer in the sun. The dark trim on a light-colored house will be warmer. You can have fun on a sunny day seeing dark-colored letters heat up enough to be able to read a sign in a thermal image. On a cloudy day the words are typically invisible!

A “Think Thermally” t-shirt differentially absorbs the sun and the lettering heats up enough to be seen clearly in a thermal image. What would this look like in the shade?

Next week, we’ll review how reflection of radiation affects our work. It is one of the most important aspects of thermography we need to pay attention to, especially if we are making quantitative assessments and measuring temperatures.

Thinking Thermally,

John Snell—The Snell Group, a Fluke Thermal Imaging Blog content partner

As we continue the discussion about convective heat transfer, it is useful to define two types of convection, natural and forced. When quantities of fluids are moved in either way, we also use the term “bulk energy transfer” because it is really the movement of the fluid itself, and the energy inherent in it, that results in the transfer.

Using a blower door forces convection. The shape and location of the various cracks and holes in the thermal envelope can result in dramatic thermal patterns.

Natural convection is powered by the difference in temperature, and thus the density, of the fluids involved. As fluids are warmed, they become less dense, and, at the same time, are also displaced by more dense, cooler fluids. As a result, warmer fluids are pushed upward as the cooler fluids sink. The greater the temperature difference, the greater the convective movement, and the more energy transferred. A summer thunderstorm is a classic example of natural convection.

Forced convection involves a pump or fan or some other means of artificially moving the fluid. Forcing convection in this way typically results in a great deal of energy being transferred. Think of how quickly the air temperature can change when a sudden windstorm springs up.

As thermographers we have to watch for the effects of both natural and forced convection. Inside a building, as anfor example, you may see a difference in temperature between the floor and the ceiling of 3-5°F due to natural circulation patterns. Outside the wind can quickly change the temperature, typically by cooling, of the side of a building or a connector in a substation. If you fail to take these changes into account, you will not be able to accurately and fully understand the nature of what you are seeing.

Other variables (aside from velocity, which we talked about last week) must be considered as well. Geometric shape and orientation to the fluid flow can both have a large influence in the patterns we see.

I often notice this around windows. This is because windows are typically either a good deal warmer or cooler than the walls, and because they also project in or out geometrically. In the winter, I can watch cool air falling across the inside of a window to chill the floor below and in the summer the effect of air being warmed by the window can be seen on the ceiling above.

Of course architects recognize this fact and often put HVAC ducts near windows to mask over these effects of convection. Look at any active heating or cooling system and you will see the affects of disruption to the moving air by the surrounding surfaces.

A blower door forces convective airflow through small cracks and holes in the envelope and their shape and location determine what the resulting thermal patterns will look like. You’ll see similar patterns around active machinery where airflow from both from the machine itself as well as the HVAC system, what is termed “spurious convection,” can result in interesting thermal signatures.

A boiled lobster has a good understanding of convective heat transfer!

The consequences of not understanding convection or not paying attention to its effects can mean making mistakes in your understanding of what you are seeing. Take the time to learn the basics and then be careful as you apply that knowledge in the field. Most of what we need to know is firmly rooted in a common sense understanding so we can all be successful if we just apply ourselves.

Next week, we’ll talk about heat transfer by electromagnetic radiation. This is important to us both because of the effect on temperatures around us, but also because our imagers detect this kind of radiation.

Thinking Thermally,

John Snell—The Snell Group, a Fluke Thermal Imaging Blog content partner

When heat transfer occurs in fluids—defined simply as non-solids—the rate and total transfer are governed by several factors, two of which are easily known: temperature difference and area. More challenging to define precisely is “h” or the Convective Heat Transfer Coefficient. This all-important variable is the amalgamation of a number of influences on heat transfer in fluids. Let’s look at the most important of them and how that might affect what we see with our imaging systems:

• Velocity of the fluid

• Orientation to the flow

• Geometric shape

• Surface condition

• Viscosity

All of these factors are important to consider, whether you are a thermographer working on buildings, industrial equipment or both. For most of our work, the fluid in question is the air surrounding us and the surfaces we are inspecting. The transfer of heat between the air and the surfaces can be considerable and can also result in patterns that can be confusing if we are not paying close attention to convection.

This remarkable image, taken by one of my students, show changes in wall temperature caused by air currents moving around and through fiberglass batt insulation in the walls of a home. Interestingly, the blower door was not being used to depressurize the home at the time!

Of the five major influences, velocity typically has the greatest affect. Whether we work out-of-doors, where we must pay attention to the wind, or indoors where air currents can have a dramatic influence, the velocity of the fluid has a powerful affect on “h” and, as a result, on total convective heat transfer. The relationship is direct: increase velocity and you increase convective heat transfer.

A simple experiment demonstrates this. Put your hand in the air and notice what it feels like. Now wave it back and forth several times. Notice you can literally feel the difference in heat transfer—cooling in this case—caused by the increased velocity of the air movement. You have, in essence, increased “h” simply by waving your hand.

If you look at the upwind and downwind sides of any building or any piece of industrial equipment influenced by air currents and you’ll see differences in surface temperature—both warmer and cooler—related to velocity.

I have found it important to measure the velocity of air movements so that I better understand their influence. This can be done very easily using any of the simple “personal weather stations” now readily available in the marketplace. Kestrel in particular, makes several fine, reasonably priced products that work well.

A personal weather station, like this Kestrel brand model, provides a simple means of quantifying both wind and air currents.

Convection is both a large and an important topic so next week we’ll continue the discussion about “h” and other issues related to convection. In the meantime, please keep your thermal eyes open and watch for thermal images showing the influences of this powerful mode of heat transfer!

Thinking Thermally,

John Snell—The Snell Group, a Fluke Thermal Imaging Blog content partner

As thermography professionals, we must be well grounded in the basics of heat transfer. If not, we’ll make mistakes in understanding, interpreting, and presenting our data. If you don’t feel 100% confident in your understanding, I urge you to move in that direction and will offer these posts as simple starting points.

Convection happens in fluids, like this cup of tea. With a carefully adjusted image you can actually see the currents of warm and cool fluid moving!

“Simple” is an important part of the process for me. Anyone doing research on heat transfer can quickly run smack into “COMPLEX!” While that approach is often necessary, let’s begin by simplifying—recognizing that the world is not always so—in order to start the foundation on which we can learn more and more “complex” later on.

Convection happens in fluids. Let’s again go back to our mug of hot coffee. When you hold your hands above the mug, heat is transferred by convection.  Your hands gain energy as air, having been warmed by the mug, moves over them. How much heat is transferred is determined in large part by various circumstances,,all lumped together and called the Convective Heat Transfer Coefficient (or h). These can include velocity and direction of flow among others. Like conduction, transfer also depends on the difference in temperature between the fluid and the surfaces with which heat is being transferred (in either direction), and, if we are concerned about total energy transfer, the area over which transfer is happening.

Newton’s Law of cooling succinctly describes conductive heat transfer:

Q = h • ΔT • A

In which:

Q = total conductive heat transfer

h = Convective Heat Transfer Coefficient

ΔT = temperature difference between the fluid and the surfaces involved in the transfer

A = Area of surfaces over which transfer is taking place

As was the case with conductive transfer, remember the net transfer can occur in either direction. Stick your finger in the hot coffee and the transfer is into your body. Once the coffee has cooled to room temperature (70°F/21°C), heat is transferred from your warmer body into the coffee.  There may be instances where the coffee and your finger are exactly the same temperature, in which case ΔT equals zero and no heat transfer happens!

We are all prone to simplifying how we speak about convection by saying such things as “warm air rises.” While this seems to describe reality, what is really true is that the less dense warmer air is displaced by the more dense, cooler air surrounding it. Think of a cork in water. Literally the cork is pushed upward as gravity pulls the water downward. “I thought we were going to keep this simple,” you say! Yes, but we also need to be accurate. You can read more (some of it just plain “hot air”) about the movement of fluids in a great online discussion on Home Energy Pros, a great website for building scientists.

Here I’m holding a piece of paper just above the neck of a thermos bottle filled with hot coffee. The heat transfer from the more buoyant warm air can be heating the paper. Is the warm air rising or being “pushed” by the cold air around it? That is an interesting question to explore!

Between now and next week, give some further thought to the issues related to convective heat transfer and take time to look at examples of convection with your imaging systems. We’ll come back to that mysterious “h” or Convective Heat Transfer Coefficient next week.

I also wanted to take a moment to wish all our Chinese friends—especially the Fluke China team and our mutual customers there—a Happy New Year of the Dragon.