Frequently Asked Questions
Q: Do you work for an IR camera company?
A: No. I am an independent scientist. I only recommend a product based on my own experience about what it can do for scientists and educators. I do appreciate those companies that offer discounts to support non-profit scientific research and science education.
Q: Which IR camera do you use to record those videos?
A: FLIR E30bx. Its specifications can be found here: http://support.flir.com/DsDownload/Assets/49001-1701_en_50.pdf. On January 7, 2014, FLIR debuted the $349 FLIR ONE, an IR imager for smartphones, which may be a better option.
Q: What is the emissivity setting for those videos?
A: 0.95 (close to those of water, paper, glass, paint, plastic, and wood at room temperature according to this website). Some materials used in our experiments may have very different emissivities that could lead to false images. To circumvent these problems, we often wrap objects up with thin paper or plastic whenever possible. If it is impossible to do so, we try our best to ensure a fair experimental condition by checking if the IR colors are approximately the same when the objects are both at room temperature. Since we are only looking for qualitative results in many experiments, the videos should be sufficiently reliable. Subtle results caused by small temperature differences close to the sensivity of the cameras have also been confirmed by using a sensitive surface temperature sensor.
Q: Which IR camera would you recommend to science teachers?
Q: How can I record a video or project to a screen using I3 or I5?
A: Unfortunately, neither camera comes with the recording or projection capability. Cameras that have these capabilities are more costly. A simple workaround is to use a webcam (web camera) to record its screen or show it on a projector. Fixing the IR camera and the webcam above the lab bench should give satisfactory results.
Q: How sensitive are these IR cameras?
A: Most of them are able to detect a change of 0.1°C immediately (as IR radiation travels at the speed of light).
Q: Why is an IR camera better than a thermometer?
A: With a thermometer you get only one data point at a time. With an IR camera, you get thousands of temperature data points at once and these data points are instantly used to create an easy-to-understand picture on the camera's screen. All you need to do is to point the camera towards the subject, just like what you do with a conventional digital camera. With a holistic image that shows the dynamic change of a temperature field, you will be able to see subtle, transient phenomena that would otherwise go unnoticed.
Q: What are the limitations of IR cameras?
A: They only detect surface temperatures in most cases. If you need to measure the temperature field in the bulk, you may insert a thin slab or a thin screen with very low thermal conductivity to "cut a slice" of the temperature field and examine it through an IR camera.
Q: I cannot afford an IR camera at present. What can I do?
A: You can use the YouTube videos provided by this website in your class. If you are not satisfied with only videos, you can try the IR experiments with a sensitive thermometer, a temperature sensor, or an IR thermometer. Most of our IR experiments are reproduciable using those measuring tools, though they take much longer time and are less appealing.
Q: What are your general advices on setting up an IR experiment?
A: In general, you should set up a "clean" thermal environment for your experiment. By "clean" I mean there should not be unwanted energy sources or sinks or heat flows in the view. For example,
- You should always insulate your experimental subjects from the lab bench. It is a good idea to rest them on a foam board.
- Use caution when handling water. If you spill water, your lab bench will appear to be cooler than the ambient temperature for as long as the water is evaporating.
- If an unwanted thermal mark (such as "leftover" heat from a previous experiment or your fingerprints) takes too long to vanish (warm up or cool down back to room temperature), use a fan to blow air towards it to accelerate the heat dissipation.
- If you need to touch the subject in the middle of an experiment, consider wearing a glove to reduce heat transfer from your hands.
Since an IR camera automatically produces an image based on the highest and lowest temperatures detected in the view scope (you should not turn this feature off because in an experiment you do not really know what temperature range is optimal for the images), a hot or cold spot from an irrelevant object will reduce the contrast of, or "contaminate," the image of the subject. If a process generates very weak thermal signals, its image will be lost in a wider temperature range. So even if you think a heating or cooling source is far away from the subject and will not affect the experimental results, you should still avoid it for better imaging results. If it is unavoidable, simply put up a screen to block the thermal radiations from it. This is especially important in the classroom where there may be many moving thermal objects—including students themselves.
Try setting up a comparison experiment whenever possible. For example, if you would like to study the heat of solution of salt, use two cups of pure water and add salt to one of them. Leave another one in the view to compare the heating or cooling effect resulting from a control condition.