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  #16  
Old 5/14/18, 5:30 PM
Chuck Evans's Avatar
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Default Re: Questions of the Week 05/13/2018

Quote:
Originally Posted by btoye View Post

Bonus: Low E coatings should be arranged on the panes to reflect IR toward the inside of the home in colder climates, and toward the outside in warm climates.
After consulting with the judges on this, they have agreed to accept your answer to the bonus question (technically, the coatings reduce the emission of heat in the form of infrared radiation)

Congratulation! You've earned bragging rights on the Bonus Question.

In very hot climates, the Low-E the coating should be on surface #2 (reducing the ability of the outer glass to radiate heat into the structure across the space between the panes). In very cold climates, it goes on surface #3 (reducing the ability of the inner pane to radiate heat out of the structure across the space between the panes).

Surfaces are numbered from the outside in: The outside surface of outside pane is #1; The inside surface of outside pane is #2; The outside surface of the inside pane is #3; the inside surface of the inside pane is #4.




Chuck Evans (TREC #7657)
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  #17  
Old 5/14/18, 5:45 PM
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Default Re: Questions of the Week 05/13/2018

Good questions Chuck. I do plan on taking a level 2 class, so I can answer essay questions.



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  #18  
Old 5/14/18, 7:11 PM
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Default Re: Questions of the Week 05/13/2018

Congratulations Brad.



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  #19  
Old 5/14/18, 9:30 PM
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Default Re: Questions of the Week 05/13/2018

Quote:
Originally Posted by btoye View Post
Good questions Chuck. I do plan on taking a level 2 class, so I can answer essay questions.
YEA Brad!
Must be da T-Shirt.



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  #20  
Old 5/14/18, 9:52 PM
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Default Re: Questions of the Week 05/13/2018

Great questions Chuck, thanks for your time. Congrats Brad!




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  #21  
Old 5/15/18, 4:07 PM
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Default Re: Questions of the Week 05/13/2018

Congratulations, Brad! He got "Bragging Rights" to the Bonus Question.




There are 4 more questions that are begging to be answered...




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  #22  
Old 5/15/18, 4:15 PM
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Default Re: Questions of the Week 05/13/2018

Good job on the bonus question Brad - and the world awaits the main answers!
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  #23  
Old 5/15/18, 5:42 PM
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Default Re: Questions of the Week 05/13/2018

Alright. To help get things going, I'm going to give the answer to question #2

2. Ordinary glass is opaque to infrared radiation.
True
False
It depends… (explain)

Answer:

It depends on the infrared wavelength. Glass is opaque to long wave infrared (LWIR), which is what most thermal imagers detect, but not short wave infrared (SWIR). If you image an incandescent light bulb with a LWIR imager, you will see the heat radiated from the glass itself. A SWIR imager can actually see the filament inside the light bulb.

The two images that I posted earlier were taken by Scott Gilligan, using his SWIR imager. The first one shows through the bulb to the reflector and you can actually see a reflection of the filament in the reflector. The second image is tuned to only show the filament.

OK so let's give everyone a second bite at the apple. The folks who have already posted a response get to take a second crack at it. As a hint, there is still one question (other than #2) that nobody has provided an adequate answer to yet - "RAT"s.



Chuck Evans (TREC #7657)
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  #24  
Old 5/16/18, 9:44 AM
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Default Re: Questions of the Week 05/13/2018

1. B
2. It depends on the infrared wavelength
3. B, C
4. F
5. up [feeling like the coffee still isn't kicking in, but thanks for the mulligan]
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  #25  
Old 5/16/18, 4:56 PM
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Default Re: Questions of the Week 05/13/2018

OK. Here's an at-home experiment for question #5 for those who have an imager at home.

Set your Emissivity to 1.00
Set your Reflected Temp to 70°F

Take an ice cube out of the freezer and shoot it with your imager (make sure you get close enough to it). Record the temperature. Now change your Emissivity to .50 and do it again. What happened to your reading?

Now set your Emissivity back to 1.00 take a glass of hot water (100°F+) and shoot it with your imager. Record the temperature. Now change your Emissivity to .50 and shoot it again. What happened to your reading?

When you change the Emissivity value of your imager, you're telling it what % of incident radiation it is detecting is coming from the object that you are observing and what % is coming from other places. Think about what process your imager is going through when you change emissivity values...

Now somebody answer this:

Decreasing the emittance value of your imager will cause the observed temperature to go ____
Up
Down
It depends… (explain)

Note: the above experiment will not give you an accurate temperature result, but it will demonstrate the process the imager goes through and provide the answer to question #5.



Chuck Evans (TREC #7657)
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  #26  
Old 5/16/18, 7:47 PM
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Default Re: Questions of the Week 05/13/2018

My Seek Reveal Pro has 5 emissivity settings, from matte (.97) to gloss (.30). It has no reflected temp setting. That being said, ice cubes at .97 measured 19 deg f, and at .30 measured 30 deg f, (more accurate). Microwaved a cup of water, at .97 measured 165 deg (more accurate) and at .30 measured 271 deg (it was not superheated boiling!)

It depends on accuracy, but the lower the emissivity setting the higher the temperature reading....
Thanks for the lesson.

Last edited by snadeau; 5/16/18 at 7:55 PM..
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  #27  
Old 5/16/18, 11:41 PM
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Default Re: Questions of the Week 05/13/2018

Steve,

Thanks for running the experiment, but unfortunately, you can't do it with your imager because it provides no control over reflected temperature. I have no idea what it is assuming for reflected temp or what it's trying to do in the way of calculation.

The four images below represent the experiment on an imager with both emissivity and reflected temperature control.

As you can see with the ice cube (looking at the spot temperature), reducing the emissivity from 1.00 to .50 causes the imager reported temperature to decrease (note: the * on the display indicates that the temperature is outside of the selected range set on the imager)

On the glass of hot water, reducing the emissivity from 1.00 to .50 causes the imager reported temperature to increase.

So, the answer to the question is:

5. Decreasing the emittance value of your imager will cause the observed temperature to go ____
Up
Down
It depends on whether the reflected temperature is higher or lower than the target object temperature. If the reflected temperature is higher than the object temperature reducing the emissivity value will cause the observed temperature to go down. If the reflected temperature is lower than the object temperature, reducing the emissivity value will cause the observed temperature to go up.
Setting imager emissivity tells the imager how much weight to give to the apparent temperature of the target object vs. the reflected apparent temperature when calculating the observed temperature from the total incident radiation.

For an authoritative reference, you could refer to the "Infraspection Institute Level-II Certified Thermographer Reference Manual" chapter on emittance.

Keep in mind that changing emissivity does not alter the image itself in any way. Emissivity only matters when you need to determine actual temperatures. It is not necessary for qualitative thermography. This is why Jim Seffrin advises Home Inspectors not to include temperatures in their reports as they can be very inaccurate if the inspector does not take these and other factors into account.

Note that the objective of this experiment was to illustrate the effect of changes to the emissivity settling, not to produce an accurate reading of the temperature of the ice cube and water glass. The values that we used for emissivity and reflected temperature were not the correct values to yield an accurate temperature measurement.
Attached Images
File Type: jpg IR_12897.jpg (171.7 KB, 6 views)
File Type: jpg IR_12898.jpg (171.6 KB, 6 views)
File Type: jpg IR_12900.jpg (171.7 KB, 5 views)
File Type: jpg IR_12899.jpg (171.7 KB, 5 views)



Chuck Evans (TREC #7657)
Level III Infraspection Institute Certified Infrared Thermographer (#8402)
HomeCert Houston Home Inspections & Thermal Inspections Find us on Facebook
The Woodlands Home Inspections
Magnolia TX Home Inspections & Thermography


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The InterNACHI Awards Committee is the final authority of issuance of any award the committee offers.

Last edited by cevans; 5/16/18 at 11:52 PM..
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  #28  
Old 5/17/18, 9:01 AM
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Larry Kage, CMI Larry Kage, CMI is offline
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Default Re: Questions of the Week 05/13/2018

Bumpity...bump...bump.




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The InterNACHI Awards Committee is the final authority of the issuance of any award the committee offers and any rules interpretation updates.
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The above post represents my personal opinion.
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  #29  
Old 5/17/18, 12:00 PM
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Default Re: Questions of the Week 05/13/2018

Very informative - thank you. The books are a bonus, but the learning keeps me coming back.
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  #30  
Old 5/17/18, 12:23 PM
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Chuck Evans Chuck Evans is online now
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Default Re: Questions of the Week 05/13/2018

Still waiting for someone to put up all 5 right answers. No more clues.



Chuck Evans (TREC #7657)
Level III Infraspection Institute Certified Infrared Thermographer (#8402)
HomeCert Houston Home Inspections & Thermal Inspections Find us on Facebook
The Woodlands Home Inspections
Magnolia TX Home Inspections & Thermography


Houston, TX
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The InterNACHI Awards Committee is the final authority of issuance of any award the committee offers.
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