Infrared Training Center

Friday, November 15, 2013

Emissivity Explained; In Plain English

itc logo (2)This short video explains thermal emissivity in a simple to understand format using thermal imaging or thermography to illustrate the concepts.

Wednesday, October 2, 2013

MSX Explained - in Plain English

itc logo (2)Have you ever wished you could have a high fidelity thermal image, but also be able to read labels and see discrete details not shown in the thermal image?

Well now you can, with a new technology called MSX.

MSX stands for Multi Spectral Dynamic Imaging, an exclusive image enhancement technology now available on several infrared cameras. This new technology is based on a unique onboard processor that provides extraordinary thermal image details in real time. MSX incorporates real-time thermal video augmented with visible spectrum definition. It produces exceptional thermal clarity to highlight exactly where the problem is. MSX ensures easier target identification without compromising radiometric data. The quality of the thermal images is excellent. There is almost no need any more for a separate digital image; MSX embosses digital camera detail onto thermal video and stills.

How does it work?

An onboard processor continually processes the visual channel and extracts only the visual detail from the visible channel. That visual detail is then added to the thermal image information. Unlike many thermal fusion technologies, the thermal information is not diluted at all, it is just augmented with visual detail not apparent in the thermal image. The result is an incredibly robust and fully radiometric thermal image displaying details and making it easy to know what is being viewed and where problems lie. See this video.

MSX Explained

Friday, September 6, 2013

Use of the Wedge Method for Emissivity and Reflection Independent Temperature Measurement

By: Ralph Rudolph
R. Rudolph Consulting LLC @
www.temperatureconsultant.com

clip_image002A technique called the Wedge Method or Roll Nip method is finding increased use in measuring strip temperatures in the metal production/processing industries as it is touted as providing the dual advantages of appearing to be independent of the material emissivity and the presence of any ambient reflected radiation. Basically, the concept is quite simple: Picture a horizontal steel strip that contacts and at least partially wraps around a large roll, usually a deflector roll used to change strip direction or a bridle roll used to set strip tension. Aim a radiation thermometer almost parallel to the strip into the gap formed between the roll and strip tangent point, as deep as you can go. (Viewing at an angle from the side is fine). This gap, as the claims state, can be treated as a blackbody with an emissivity of 1.0 (see Figure 1). Hence, you don’t have to worry about ambient radiation as reflectivity is 0.0 and you don’t have to worry about changing material emissivity. This is partly true and partly wishful thinking.

Blackbody conditions exist for a cavity if and only if all sides of the cavity are at the same temperature. If the roll being used has a very low thermal mass (heats up easily) and there is a large wrap around the roll and sufficient strip tension to allow heat transfer to occur between the strip and the roll, then the roll will heat up to near strip temperature over a time period, but because the roll has natural convection, conduction and radiation losses, the roll can never quite reach the strip temperature. Emissivity never reaches 1.0. It should be obvious that if the strip abruptly changes temperature, which can happen with strip thickness or furnace temperature changes, it will take time for the roll to change temperatures. Heat transfer between the two can take quite a while during which time the temperature reading from the wedge system will be quite inaccurate.

Wedge or cavity measurement method
Figure 1.

So, if a system is designed well, with a major roll wrap, low thermal mass roll, sufficient strip tension and steady long term operation (no major changes in strip temperature), this method can work as claimed (except that emissivity must be set somewhat lower than 1.0 to compensate for the roll being at a slightly lower temperature than the strip).

Given human nature, however, I’ve seen numerous instances where folks have not understood why the wedge method can work and who have misapplied it. Believe it or not, I’ve seen an instance where a so-called wedge method has been applied with zero roll wrap, with the strip simply passing over a support roll. And this system was (unfortunately) designed by the equipment provider who should have known better. I would guess that a majority of wedge method applications that I’ve seen have been poorly designed, with little attention paid to the amount of roll wrap or roll material and with little understanding of what occurs during changes in strip temperature.

There is a modification to the wedge method that can provide a significant improvement: Mount a second Radiation Thermometer to monitor roll temperature and compare this reading to that of the wedge RT. Using a PC with input and output cards (and most any older PC will work), abrupt deviations between the two readings which occur as strip temperature changes can be used to correct for errors. If accuracy is desired, it’s well worth the extra expense. You get what you pay for.

Monday, August 5, 2013

Online Introduction to Outdoor Electrical Surveys using IR Thermography Course Updated

Menu SlideThis introductory course is designed to give you a straight forward explanation of how Infrared technology fits in the outdoor electrical inspection industry. This course earns 1 ITC Certification Renewal Credit.

Students' Course Rating: 4.3/5


Updated 2013-08-05: added professional narration, improved graphics, interactive knowledge checks, glossary, search, slide notes, navigation with menus.

Objectives

  • An overview of a outdoor electrical survey goal and process
  • An outline of industry guidelines and standards
  • A demonstration of images and analysis
  • A summary of reporting capabilities
  • A briefing on additional accessory tools

Course Home Page

Wednesday, May 8, 2013

Optical Gas Imaging Re-Certification Exam Now Available

itc logo (2)The Optical Gas Imaging Recertification Examination is designed for the Optical Gas Imaging thermographer who needs to recertify an ITC Optical Gas Imaging certification. The prime candidate is a thermographer who has been unable to accumulate 32 certification renewal credits (by attending IR conferences, other IR courses, and/or writing/presenting articles and papers) during the 5 years of his certification validity. Payment is by credit card.

Click here to go to the Exam Home page

Thursday, April 4, 2013

Using a Wide Angle Lens as a Macro or Close Up Lens

itc logo (2)Some thermographers are surprised to learn that many wide angle lenses can be used for high magnification work. After all, the wide angle lenses have a larger IFOV and IFOV footprint, so how can they be used for small targets effectively?

Here is a typical example for a FLIR E60 camera (320 x 240 resolution):

Lens FOV IFOV (mrad) IFOV footprint at 19.7” Working Distance
25° x 19° 1.36 0.03”
45° × 33.8° 2.59 0.05”

The specs above don’t indicate that a wide angle lens is any better, in fact it has a larger footprint. So what gives?

Take a look at the thermograms below:

E60 25 deg lens full FOV macro Here is a thermogram of a ruler taken with the standard 25° lens at its closest focus distance of 9.2”.

Note how the scribed lines on the 100ths scale are fuzzy and merge together. The horizontal FOV is about 3”.

This indicates that items this small cannot be resolved using this lens.
E60 25 deg lens Zoomed FOV to match 45 deg lens macro I have enlarged the 25° image to illustrate the blurred lines on the scale.
E60 45 deg lens full FOV macro Here is the same ruler taken with a 45° lens. The scribed lines can clearly be seen and differentiated. The horizontal FOV is about 1.5”.

What’s the secret? The 45° lens can be focused much closer to the target (1.2”). Hence it effectively can resolve smaller targets.

Does a wide angle lens work as well as a dedicated close up lens? No, of course not. You might notice that the sharpest areas are in the middle of the image. A dedicated optic for close up work would be designed to reduce this effect while achieving higher magnification.

But as a dual purpose optic, when you need to do some close up work, a wide angle lens is pretty handy.

Here are some images from a FLIR P640 for comparison.

24 Deg lens

46 deg lens