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Infrared Tips and Tricks
1) Focus and Compose! You can improve a thermogram in some ways after it is stored, but you will never be able to improve the focus or to remove spurious thermal reflections! Get it right the first time and you will save yourself a trip back to the field. Focus carefully! If reflections from hot or cold sources from overhead or in the background impinge on the target, try changing your position to minimize or eliminate them. (This is the “Fo” of the acronym FoRD—Focus, Range, Distance.) 2) Choose the Right Temperature Range Do you know the range of temperatures that you are going to be imaging? Be sure so that you can set up your camera with the correct range to view the temperature range correctly. When observing the target, fine-tune the temperature span of your camera to produce the best possible image. This will affect both the quality of your thermogram and your temperature measurement accuracy. (This is the “R” of the acronym FoRD—Focus, Range, Distance.) 3) Know your Maximum Working Distance If you are measuring target temperature, be sure you know the maximum working distance from which you can obtain accurate temperature measurement. With an uncooled bolometer FPA, the target image passing through the camera’s optics must occupy at least 9 pixels of the FPA—and preferably more, to be accurately resolved. If the camera is too far from the target, the target spot will be too small, and the accuracy of the resulting temperature measurements will be compromised because the camera will average the temperatures of the target spot and the environment. As a general rule, the closer you get to your target, the more accurate your temperature measurements will be. Getting close helps maximize the camera IFOV across the target, providing better resolution. Show just enough of the scene to enable someone to identify the target. Never get closer than the minimum focal distance of your camera optics or you won’t be able to focus the image. (This is the “D” of the acronym FoRD—Focus, Range, Distance.) 4) Do you have to Measure Temperature (quantitative) or Simply Produce a Clear Image (qualitative)? What’s the difference? A quantitative thermogram "measures" the temperature of a condition. A qualitative thermogram can document that a thermally noteworthy condition exists. A sharply focused image is critical to both, but if the task is to measure temperature and it’s possible or likely that you’ll be asked to compare and even trend temperatures of the same target over time, be sure to record all target and environmental conditions that could affect measurement accuracy: e.g. emissivity, ambient temperature, wind speed and direction, humidity, reflected heat sources, etc. 5) Keep the Background Simple When working outdoors, for example, doing utility inspections, you will find that most targets are close to ambient temperatures, but the sky is very cold. You can silhouette the target against the sky to focus attention on the target. Avoid visual obstructions: the effort will pay off in your thermograms. When working outside, be sure to consider the effects of solar reflection and solar gain on your image and temperature measurements. It may be necessary with older types of infrared cameras to work at night to eliminate the solar reflections that masquerade as fault hot spots. 6) Hold Your Camera Steady All current longwave FLIR cameras have fast, 60-Hz frame rates, but many older infrared cameras have much slower frame rates, inviting blurring due to camera movement during the recording of images. As a matter of best practice, all cameras should be held as still as possible when freezing and recording an image. When you press the “store” button, do so gently and smoothly. Even slight camera movement can rob your pictures of sharpness. Use a brace to steady your arm, rest the camera on a convenient surface, or use a tripod. 7) Camera Maintenance and Lens Cleaning The camera body, cables and accessories may be cleaned by wiping with a soft cloth. To remove stains, wipe with a soft cloth moistened with a mild detergent solution and wrung dry, then wipe with a dry soft cloth. NOTE: Do not use benzene, thinner, or any other chemical product on the camera, the cables or the Accessories, as this may cause deterioration.
Lenses
All lenses are coated with an anti-reflective coating and care must be taken when cleaning them. First and most importantly, always blow off loose dirt; using a compressed air line (free of moisture) or a can of compressed (canned) Air (i.e. “Super Duster 134”), commonly found at computer/electronics suppliers. Next use a soft cotton ball/cloth, Q-tip, or Kleenex type tissue (no Aloe or other additives), soaked in Acetone (also with no additives or 96 % ethyl alcohol may be used) to gently clean the lenses surface. The lenses should be wiped once with the solution, and then discard the cleaning medium and prepare another. If ethyl alcohol is unavailable, DEE (i.e. ‘ether’ = diethyl ether) may be used for cleaning. Sometimes drying marks may appear on the lenses. To prevent this, a cleaning Solution of 50 % acetone and 50 % ethyl alcohol may be used.
NOTE: Please note the following:
- Excessive cleaning of the lenses may wear down the coating.
- The chemical substances described in this section may be dangerous. Carefully read all warning labels on containers before using the substances, as well as applicable MSDS (Material Safety Data Sheets). 8) E/B/P/S Series Battery Charging These new Lithium-Ion batteries provide an operation time of approximately 2 hours and when “Battery Low” is displayed on the screen, it is time to charge the battery. If you do not remove the battery at this point, and continue to operate the battery beyond this warning, then the camera continues to run but will shut off on it’s own accord when completely dead or when you are able to replace it. The problem with this is, the battery charging pattern can be severely disrupted, the battery can be severely damaged and/or the battery may not seem to charge properly once it is placed back in the charger. By ‘properly’, I mean the battery charger will have a ‘flashing red light’ and after the normal charging time (about 1 hour – which is normally required at the ‘Low battery’ warning level) the charger is still flashing red and most people assume that the battery is now faulty. WRONG! If you now continue charging the battery for about 2-4 hours in total (or overnight) and then you look at the charger after waiting this extra time period, you may still see a flashing red light, but lift the battery out of the charger and wait a few seconds, then place it back in the charger; the lights should change back to the green ones (solid green and flashing green ones) indicating that it is now recovering and still may require a topping up. Save yourself a headache and some cash, always charge your batteries asap after seeing this ‘Battery low’ warning … it’s there for a reason!
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