by Maurice Lee MIIE(mech),
A motor industry Test Engineer with 30+ years experience

In the automotive testing world the IR camera is an extremely useful tool. Here are a few examples of how I have used the technology.

Reduce Defroster Testing Time!

The design of windshield defrost demist ducting is complex, hampered by the dimensional constraints due to other essential vehicle parts, it is awkward to say the least to provide an adequate and evenly distributed airflow to the inner face of the glass.

To validate a design, a typical defrost development test is as follows:-

Following design guidelines for the intended market a vehicle needs to be chilled to
-20°C or so and soaked (to achieve uniform temperature) for up to 8 hours to ensure a known start point. The windshield has a known amount of water sprayed on and is left to cure for several minutes to establish uniform crystal consistency. The vehicle engine is started and allowed to idle with the appropriate heater/windshield defrost settings.

As the engine heats up and warm air flows through the defrost ducting, a thaw pattern develops on the screen.

At set intervals, a recording is made of this thaw pattern and a certain area of glass must be clear of ice within a predefined time, as defined by the Testing Standard used.

Processing these results takes some time and if the defrost system provides uneven or inadequate thawing and needs improvement, the whole costly process needs to be repeated (often for several iterations of duct design).

If an IR camera is used looking at the outside of the glass while using the same test conditions, but with the vehicle stabilized at normal lab ambient (say 20°C); a thermal pattern appears on the glass within a couple of minutes. This pattern, once formed, does not seem to significantly vary in shape, only in intensity.

Design alterations can be made to the duct and outlet apertures and minutes later the process can be repeated. Once the desired pattern is achieved, the expensive ‘cold’ test can be attempted.

Of course this method does not initially guarantee success, as time has not been a factor in the process but uniform or desired temperature distribution can quickly be resolved.

The thaw process starts due to a certain glass surface temperature. If an IR camera is used to record a low ambient defrost test; time, glass temperature, and thaw pattern data can be collected.

If the same vehicle is then allowed to achieve normal ambient throughout (e.g. +20°C) and a ‘warm’ repeat of the defrost test is carried out, there will be a correlation between the glass temperatures in relation to time.  It should therefore then be possible to carry out defrost development tests with reasonable confidence at ambient conditions.

Editor's note: Image subtraction can be a powerful image processing tool for applications like this. Very often there will be unwanted reflections from overhead lights or other heat sources that you will see from the glass. By taking an image before the defrosters are turned on; and then subtracting that image from the images captured during the test, you can effectively eliminate the spurious reflections and display only the changes caused by the air flow.

See the "air"!

Automotive Heating Ventilation & Cooling (HVAC) engineers face the challenge to establish and maintain comfortable ambient conditions within vehicles.

In order to test new or modified systems the passenger compartment air circulation needs to be measured in some way. Air movement around a vehicle is quite slow, the fastest within the passenger compartment being at the outlet of cooling/heating vents.

These outlets are quite small in size, if measuring equipment is placed in the airflow it can both disturb and restrict, thus affecting the measurements being taken.

As with windshield defrost ducting, climate control ducting is a complex shape made to follow a tortuous route. The airflow from most ducts is often very difficult to direct into a laminar uniform pattern. Any information about the actual pressure/flow profile from a duct can assist in design improvements.

There is a product available which is a paper composite material formed in a sheet of honeycomb perforations.  Using an 8mm thickness with a honeycomb size of 4mm with a paper wall thickness to the cells, placed at 90 degrees to the airflow it presents very small disturbance or restriction.

Being made of paper, it conducts heat poorly while due to its depth (contact area) and small mass readily assumes the temperature of the air passing through the honeycomb.  If an IR camera is directed at the honeycomb, but in the airflow, the camera bulk will restrict the airflow and the image will be of the thin edges of the mesh.

If the camera is angled at the honeycomb sufficient to ‘blank off’ sight of the airflow source, the image will be of the inner walls of the honeycomb, which is radiating the IR waves allowing the IR camera to measure the temperature of the air flowing across it.

Uneven air distribution from a vent will readily display a temperature profile across the target area. This alone can be used to develop duct and outlet design.

Maurice receives an InfraMation Executive Attaché Case for his newsletter contribution. Published articles also earn credit towards IR recertification

• Reality TV Hots Up as UK Channel Airs Sex Videos
  Reuters, NY - Nov 22, 2004
  Channel 4 insisted that the show, which will feature videos filmed using thermal-imaging to minimize their graphic nature, was designed to help rather than ...

• WEVA: On the Move
  TheHorse.com, KY - Nov 21, 2004
  ... with thermography before using scintigraphy. Knowledge of how to use the equipment, and what indicates a problem, are key to successful thermal imaging, noted ...

• Mission: preserve and protect
  Richmond Times Dispatch, VA - Nov 21, 2004
  ... restoration contractor GBG Inc. used ground-penetrating radar, metal detection, thermography and ultrasound. Combining the results ...

• Emergency Response System Delivers Maps in Record Time
  Yahoo News (press release) - Nov 19, 2004
  ... the wake of September 11, 2001, when EarthData utilized a multi-sensor approach to map Ground Zero with digital imagery, laser terrain data, and thermal imaging ...

• Preliminary Study Tackles Wind Power, Bat Issues
  SolarAccess.com News, NH - Nov 9, 2004
  ... Staff and interns for BCI compiled all of the data they gathered through physical searches, thermal imaging, radar studies and ultra sonic detection records ...

Here is a selection of recent new threads by IR Community members. Feel free to click the links, see how people have responded, and post your own response if you like.

• Calculating Insulation U Values
  I am trying to calculate overall U Values for a building based on internal/ external temperatures.I know this should be fairly straightforward provided i take all variables into account. I need a formula to help with this, I have tried several, but none of them give me great confidence.

• Tank Car Testing
  We were asked to check the integrity of the insulation of a carbon dioxide car. Anybody do this yet and/or any ideas?

• Business Plans
  Now I know many or most of you operate as employees of a larger operation. I am interested whether anyone operates independantly - freelance small business - and has written a business plan for IR work...and if you'd share.

• Hot spots and motor efficiency - Still more Q's
  My question now is more specific to hot spots in the circuitry. I'm wondering if we can draw any correlation, even to within some reasonable range, of motor efficiency degradation and, say, a 150°F hot spot on a single leg of its power supply on a lug at the breaker or mag. Say the motor is only a couple of years old and rated as a premium efficiency unit.
   

• IR for steam leaks
  Yesterday I walked by one of our flash tanks and heard a hissing noise. I had a feeling that we had a leaking sight glass gasket so I took our Flir e-4 camera and scanned around the sight glass. Couldn't see anything, so I took a piece of plastic laminate and lo and behold found the leak. I scanned the laminate and could see the leak. My question is; Why could I not see the leak area without putting the laminate there to "catch" the steam? Is it possibly because the leak was minute and ambient conditions were higher than the leak area, or am I totally "off base" here. Could I use the manual settings instead of auto and see it?

• IR scan of heel
  Medical IR is not my forte, and do not intend to pursue it, but I guess I have a little "Curious George" in me. I have what I believe is a heel spur and out of curiosity "shot" both my heels just to see if there was a difference. Here are the scans. Why would the bad heel appear colder in the spot that is giving me pain?

And of course if YOU have a question or want to start a discussion on a topic, we would love to hear from you. Just post a new thread on a message board.

Brainteaser of the Month  [top]

Here is this month's brainteaser. Readers who email us the correct identification and explanation of the object(s) in the thermograms are entered into a drawing to win a prize from ITC. Please put "Brainteaser" as the subject of the message.

Click here to email your guess

Do you have an interesting image that you think would stump other thermographers? If so please email me your image (preferably in native .img, .jpg, .tif, .tgw, or .tmw format) with an accompanying visible photo and explanation. If your image is used, you receive a gift as well.

Some readers believe that these circles were UFO's or aircraft warning balls. Nope, just some dishes from a communications tower in the background.

Congratulations to our winner, Pierre Duval from the Naval Station at Newport, RI and a thank you to Alex Farías Santodomingo all the way from Columbia for the thermogram. Both Pierre and Alex receive a special ITC low emissivity traveling coffee mug.

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