Choosing a Thermal Imaging Camera: Some are “Hot,” Some Are Not
A thermal imaging camera plays a central role in identifying failures in electrical systems or components before they happen.
By Scott Black
Advanced New Cameras Are More Precise, Easier to Use Than Older Designs
A thermal imaging camera plays a central role in identifying failures in electrical systems or components before they happen. While the technology is relatively advanced, the concept is simple: since nearly everything gets hot before it fails, thermal inspection is a valuable and cost-effective diagnostic tool with many industrial applications. Since typical electrical failures occur when there is even a minor temperature rise, problems can be detected well in advance of a failure. Consequently, temperature is the optimal method to know if an electrical system or component is working properly or will soon be subject to operational distress.
Thermal imaging identifies the transfer of infrared heat radiation from an object and provides the means to scan the thermal emissions of various surfaces and display an image of temperature distribution. Specialized detectors in an infrared camera capture the smallest variations in temperature, and with the infrared camera, an inspector can see the change in temperature from the surrounding area, identify whether or not it is abnormal, and predict possible failure.
Once a highly specialized and very expensive technology, now affordable thermal imagers are used to detect heat rises caused by the faulty operation of an electrical connection, motor, bearing, or even a deteriorated insulator. This affordability has arrived not a moment too soon: most of these types of problems would otherwise go unnoticed until a failure or an expensive tear-down. Clearly, avoiding such a disaster helps the thermal imaging camera pay for itself in an extremely short time.
Based on its functionality and ability to minimize the chances of expensive equipment failure, adding a thermal imaging camera to your in-house electrical predictive maintenance program is a virtual no-brainer. The question is, which one is best suited to your company’s unique requirements? Following are some criteria that should be considered before making this important purchase:
All thermal cameras will provide a thermal image of a trouble hotspot. Having the ability to provide a visual image, however, is a major plus in providing context. The visual image can subsequently be inserted into a report for presentation to the client, making it easier to understand the exact nature of the issue, including its location. In some instances, companies are providing cameras that are able to combine or overlay the thermal and the visual image, a third mode referred to as “fusion.” Ultimately, overlaying the rich detail of an infrared image on a high-resolution visual reference image can provide greater insight to what is being displayed in the infrared image.
What’s more, if the image is scalable, it can include as much of the visual or the thermal as is necessary to convey the information—for example, the operator might generate a large visual image of a problem area device, but only use a small thermal image in the center to highlight the actual trouble spot.
While most “pistol-grip” thermal imagers on the market do include some visual camera capability, the image resolution is often equivalent or inferior to that of a camera phone image. A poor-quality visual image-as well as an equally low-quality thermal image-can detract from report findings and may mean additional follow-up readings: what this means is that resolution is of critical importance in the selection of a thermal imaging camera-and resolution means pixels.
There are cameras available with a wide selection of pixel ranges: “typical” thermal imaging cameras offer 120 x 120 (14,400 total) and 140 x 140 (19,600 total); cameras available containing 180 x180 pixels (32,400 total) provide superlative resolution. Ultimately, additional pixels mean more valuable and accurate temperature information to isolate electrical problems. For industrial plant managers, electrical contractors, and building inspectors, more infrared resolution results in simplified analysis and higher quality findings.
Some cameras are equipped with larger screens than others. Virtually any size screen, from 3.5-inch color LCD’s and above, provides easy-to-read displays, which allow the technician to discuss preliminary findings with a client by referring to images using his camera screen. In such a case, a bigger screen can help show a hot spot more easily, before an official report is produced.
The better cameras, with their more tightly designed infrared detector arrays, provide temperature measurement accuracy as high as 2 percent and 100MK (0.1°C) thermal sensitivity, which translates to more accurate and conclusive findings. Much of the accuracy of the instrument, though, is derived from its pixel count, and the increased resolution will provide many more points of temperature information. When a user needs to find the actual source of a hotspot, increased resolution amounts to increased precision in identifying problems. When the camera has to do any averaging, it will contain far more information to start with.
Quality cameras are also capable of performing within a wider temperature range. The ability to generate accurate measurement at -20°C to 350°C is a more-than-acceptable range.
Ease of Use
Cameras all rely on menu-driven functions and “soft-keys,” a set of buttons that change function depending on which menu is in use, as displayed by corresponding tabs on the screen. While some cameras boast simplified functionality by offering as few as three buttons, this limited number of buttons means that most basic functions require extensive multi-step routines, forcing the user to click through several menus to get to a basic task or setting. Conversely, cameras that feature “hard-coded” buttons provide direct access to frequently used functions. Additionally, more sophisticated navigation pads make it easier to get to a desired function or setting more intuitively, with fewer clicks.
Power Supply/Battery Life
The last thing a technician wants is to be out in the field and have the camera’s battery die; thus, the longer the battery life, the better. If the battery does lose power, it’s imperative to be able to switch to a spare battery quickly and easily. On some cameras, the battery isn’t removable by the user, meaning that the camera must be plugged in to charge, similar to a cell phone. Consequently, the camera can only be employed as far as the cord will stretch, or the operator has to walk around with an extension cord.
A long-lasting (five-hour) field-swappable Lithium-Ion (Li-Ion) battery ensures that a fresh battery can be inserted and the operator can keep working. What’s more, there is no need to take the unit out of service for factory battery replacement when the battery no longer charges. Easy replacement, Li-Ion battery technology, unlike older nickel metal hydride (NiMH designs), is less susceptible to “memory effect”-that is, it can be recharged everyday after you use it and it will fully charge, not only up to the point of its last use.
The issue of durability is a crucial one, given that the camera is going to be deployed in a variety of harsh, industrial environments. Further, given that some of the measurements will be taken in awkward spots or under equipment, there is a high likelihood that this costly piece of equipment will be dropped at some point; thus, impact resistance is an absolute must.
The durability of the camera is generally derived from its overall design, rather than any specific features. Double-molded housing is instrumental in providing the requisite impact resistance, and dust-proof construction will keep harmful material out of the camera’s sensitive mechanism. Smaller cameras also fit more easily into a holster, signifying that carrying the camera safely doesn’t have to be a decision between holding it in your hand or constantly having to stow and retrieve it from a carrying case.
It should also be noted that some popular infrared cameras rely on older designs, which, as with most electronics, are generally larger and heavier. Thus, while some vendors portray their bigger cameras as being “built like a tank,” the reality is that the new, smaller, lighter cameras are often more rugged and powerful, even with their smaller footprint.
Furthermore, a camera that features a lightweight ergonomic grip design is critical, as it will make all-day, one-handed, “point and shoot” operation easier with less strain on the user. High-resolution, fully featured cameras as light as 1.3 pounds can be found on the market, whereas some pistol-grip cameras on the market weigh twice as much.
Image Storage Format
The format in which the images are stored is an important consideration. It’s best to use a camera that stores files in a common format, such as the JPEG format, unlike some of the different formats used by some cameras which no one else will be able to read, unless they’re using proprietary software that is often required.
With a popular format such as JPEG, the camera can be plugged into any computer with a USB cable (or the memory card can be transferred to a card reader) and the images can be transferred and sent as e-mail attachments or inserted in Word documents for easy sharing with anybody. What’s more, you should look for a camera in which the JPEG images preserve all of the embedded temperature data. In other words, a JPEG may pass through several recipients and the temperature data is never lost.
As a point of contrast, some camera makers rely on two image formats: a proprietary one for preserving temperature, or radiometric, data, and a more mainstream format, such as bitmap (BMP) where the temperature information is stripped out for the sake of sharing. Oftentimes, generating such a shareable format is a cumbersome, multi-step format that relies exclusively on the camera’s proprietary software. The challenge with this is that a technician who wants to share an image with a client while on a job site must download the image to his/her laptop, import it to his camera’s proprietary software, go through several steps to export it as a BMP, and then share it. Using a format such as JPEG, a client could directly access shareable images right off the memory card, or the camera (with a USB cable).
The longer a technician can operate the camera without having to download the images-thermal, visual, or fusion-the more productive he or she can be. For that reason, the image storage capacity of the device should be as large as possible, eliminating the need for the technician to stop taking measurements in order to clear the camera’s memory card.
Image storage, it should be noted, goes hand in hand with resolution: the higher the resolution of the images, the more space will be needed to store them. Accordingly, buying a high-resolution camera with a low storage capacity would be an imprudent purchase.
Low-light areas like electrical cabinets, storage facilities, or nighttime spots will create dark visual images that can hamper the ability to illustrate problems effectively. To combat this, a few infrared cameras are available with a built-in illuminator lamp, helping to assure quality images even in the most dimly lit areas.
The optimal thermal image camera features reporting software powerful enough to create professional-looking reports while relying on an easy-to-use and convenient template approach, so that the user is not “reinventing the wheel” each time a report is generated. Further, the camera’s software should offer a simple procedure for integrating pictures with the text and producing a report that can be more easily understood.
As mentioned above, some cameras lose significant functionality when a computer containing proprietary reporting software isn’t nearby. This is due to the fact that the software serves as the critical link to take the camera’s proprietary image format and export popular, easier-to-share images. Cameras employing popular image formats such as JPEG obviate the need for such exports and really only rely on software for creating reports.
While most thermal imaging cameras are relatively easy to use, training can ensure that the operator is able to use the device to its best advantage. Choosing a vendor that offers industry-recognized training on its cameras is critical. Additionally, look for training that is available both in-class and online. This serves as a valuable mix for substantial, upfront, up-skill learning and accessible continuing education.
Which One to Choose?
No camera is right for every thermal imaging task. However, if you can identify a camera that fits the preceding criteria, it is likely you will have a camera that will offer superior performance for the vast majority of field applications.
Any consideration of thermal imaging cameras should include the recently launched i-Series from FLIR Systems. The three-camera FLIR i-Series range-the i40, i50, and i60-meet all of the critical parameters of thermal imaging applications. What’s more, they offer significant ease of use to help in-house plant maintenance, electrical and HVAC technicians, building inspectors, and professional thermographers alike find problems faster and more easily.
But whether you purchase the i-Series or another camera for your thermal imaging jobs, it’s wise to find a device that meets as many of the preceding criteria as possible. In doing so, you’ll have a camera that’s versatile and flexible, while keeping your capital investment to a minimum.
About the Author:
Scott Black is a product manager at Extech Instruments, a subsidiary of FLIR Systems, Inc. Black has been at Extech for five years and has over 22 years of experience in the instrumentation business.