Magazine for the auto service professional
Issue link: http://asp.epubxp.com/i/780462
16 | ASP February 2017 Technical will show temperature data along with the image. Most tools store the image as a jpg file on a removable SD card, and some tools can also download the image through a USB connection. e tools you'll find at places like Home Depot and other big-box stores are best suited for industrial or residential applications. ey can focus to infinity and some have a visual-light sensor to enhance the image display. What they probably don't have is a big thermal image sensor. A bigger sensor captures a more detailed thermal image, and that's what you need for automotive work. e spec sheet of most tools lists the pixel size of the display screen, but unless the specs also show the size of the thermal sensor, you have no way to compare it with other tools. e next step up in price is where you'll find imagers that are useful for automotive work. ermal range, accuracy and sensitivity will be more than adequate on all of them. e more important differences from one tool to the next include image display options (zoom, color palate, etc.) that make it easier to detect more subtle temperature differences. e more expensive models include an optical sensor to add visible light details to the image. When comparing thermal imaging tools, the most important specification is the size of the thermal sensor. By its very nature, a thermal image is fuzzy around the edges, and a low-resolution image can appear as a poorly- defined blob of heat energy. While a built-in optical sensor provides useful detail, a bigger thermal sensor provides a sharper thermal image; that's where to spend your money. ermal imagers with a really big sensor can cost as much as a scan tool, but there are several models at lower price-points with a decent-sized thermal image sensor. Some thermal imagers are made specifically for automotive work. ey include built-in software with guided tests and a library of images showing known-good and known-bad components. is can make the tool easier to use right out of the box, and it can also help you explain your test results to the customer. e next step up in price range buys a tool that can produce thermal images almost as clear and detailed as a photograph. Most are complicated to use and are specifically designed for documenting scientific research or industrial inspections. ey are also very expensive, some costing as much as a new car. What can it do? Like all automotive diagnostics, most of the problems you can find with a thermal imager can also be found with other tools and tech- niques. But as noted earlier, a thermal image can visually show you the problem, saving time and giving you more confidence in your diagnosis. For example, the image in Figure 1 shows a warm spot inside the headliner of an Acura MDX. e vehicle's battery was being drained overnight, and the tech found a 230 mA key-off current draw at the battery. Honda/Acura models are known for faulty cell phone Hands Free Link (HFL) control units that stay active with the ignition turned off, and the thermal image quickly confirmed the This Acura cell phone link control unit remained active with the ignition off, draining the vehicle's battery overnight. Its temperature was only a bit above ambient, but that was enough to confirm the tech's suspicion without having to measure circuit current draw. Photo courtesy of Ronald Leverett