What to Look for in a Thermal Imaging Camera
There are a number of components that contribute to both the quality and the cost of a thermal imaging camera. The two most important factors are the detector resolution and the thermal sensitivity.
The detector resolution describes the number of pixels. The most common resolutions are 160 x 120, 320 x 240 and 640 x 480 pixels. A 320 x 240 detector produces an image composed of 76,800 pixels. Since each pixel has a temperature associated with it that is 76,800 temperature data points. Higher resolutions also produce visibly clearer images.
Thermal sensitivity is the smallest temperature difference the camera can detect. A sensitivity of 0.05° means the camera can distinguish between two surfaces with only a five-hundredths of a degree temperature difference.
Another important factor to consider is the thermal imaging camera’s temperature range. The range tells what the minimum and maximum temperatures are that the camera can measure (-4°F to 2200°F is typical).
To obtain the best thermal image to analyze, there are four adjustments that can be made to most cameras: focus, emissivity setting changes, reflective temperature setting changes and thermal tuning. Each of these adjustments must be considered when selecting a thermal imaging camera.
Just like a standard camera, the lens of the thermal imaging camera needs to be focused to enhance the clarity of the image. Most cameras can be focused by twisting the lens. More sophisticated cameras have a push-button focus.
Emissivity is the amount of radiation emitted from an object compared to that of a perfect emitter of radiation when both are at the same temperature. Adjusting the emissivity is important when taking temperature measurements or when comparing the temperatures of two different objects. Not all cameras allow the user to input reflective temperature.
The reflective temperature setting allows the user to compensate for surrounding objects’ temperature reflecting on an object. Just like emissivity, reflective temperature is important when taking temperature measurements or comparing two objects’ temperatures. Not all cameras allow the user to input reflective temperature.
Thermal tuning the camera involves adjusting the span or temperature range that the camera sees while in manual viewing mode. Manual mode allows the user to adjust the span to a desired range, and the camera will always display this temperature range. Using the manual mode is best when used to bring out temperature differences of the object being viewed.
Thermal Imaging Camera Limitations
Because thermal energy can be reflected off shiny surfaces, thermal imaging cameras cannot see through glass. Thermal imaging cameras can be used to gather information about the inside of a wall, but they cannot see through walls. It is also important to know that thermal imaging cameras should not be used as the only deciding factor that a problem exists. Using other instruments should always be used to confirm the problem.