A thermal imaging camera is quite expensive. This is practically the price of a mid-range smartphone, not far from even the high end! Whether it's Android, Apple or single thermal imaging cameras. We are talking here of a few hundred euros for the cheapest to several thousand euros for professional thermal imaging cameras! I bought the HTI HT-102, Android thermal imaging camera in USB-C, which is much cheaper than the classic brands like Flir or Seek, specialists in the field, to see what it had in the belly.
What is a thermal imaging camera?
A thermal imaging camera can detect heat differences from one point to another. It captures infrared radiation and transcribes it as a temperature zone. Generally, you have a beautiful dark red for a very warm body and a green area for a colder body. Generally speaking, you can change these colors, but these are the most used colors I would say. Beware, unlike the film you make in your head, a thermal imaging camera does not allow you to see a body that emits heat through a wall, a door or any other obstacle! Infrared radiation is simply blocked.
The difference between thermal and infrared camera
An infrared camera and a thermal imaging camera are not used in the same way. Although both types of cameras use infrared radiation emitted by a body or object, sensitivity differs between the two.
The infrared camera
The infrared camera captures wavelengths in the order of the micron. It is mainly used in the dark and with additional lighting to film night scenes. For television or hunting for example… Infrared cameras usually give images in shades of white-grey, slightly pink/purple. Landscape in shades of grey taken by an infrared camera
The thermal imaging camera
While the thermal imaging camera captures wavelengths in the order of one-tenth of microns. Sometimes called heat waves, they are directly related to the temperature of the body or the object that produces them. As a result, it is used to measure the thermal emissions of a place and can detect temperature differences on an electrical installation, insulation defects on a building, etc. Like the infrared camera, thermal can also provide images at night, with better image quality and no additional lighting. The images are in several colors depending on the temperature: blue, green, yellow, red. Colors that can be changed generally. 
The test of HTI HT-102, Android thermal imaging camera
An important criterion is price. The HTI HT-102 costs a hundred euros. The best known like Flir or Seek range from about 250 euros to 500 euros… There is an Apple version, which is the HT-101 model.
Features
- Model: HT-102
- Color: black
- Material: metal
- Temperature range: -20 to 300 degrees Celsius
- Accuracy: 3 degrees Celsius or 5% of reading
- Resolution: 0.1 degrees Celsius
- Workband: 8-14 m
- Horizontal angle of view/ vertical angle of view: 43 degrees Fahrenheit.
- Infrared image resolution: 32 x 32
- Visible image resolution: 640 x 480
- Image format: png
- Video format: mp4
- Image frequency: gHz
- Focal length: fixed
- Operating temperature range: 0 to 35 degrees Celsius.
- Storage temperature range: -20 to 60 degrees Celsius.
- Taken: USB Type-C and Android.
- Power: Power from external devices, such as Android phones
- Dimensions: 59 x 30 x 12 mm.
- Weight: 19g
The content
The HTI HT-102 is very well packed, you have a big block of hard foam. In addition to the thermal sensor, you have a plastic transport box with the foam inside pre-cut to match the shape of the sensor. In addition, you also have a micro-usb/usb-c adapter. So it's perfect for transport, but also for compatibility with your smartphone. Even if the latter does not have a USB-C port, the adapter is there to solve the problem.
HTI HT-102
The HTI HT-102 is used with the "Thermal Viewer" app. The app allows several things:
- take a normal photo
- capture a thermal image
- have a photo with thermal image overlay
- change colors for the thermal image
- Know the temperature of a particular point
- Film
When you read the comments on the Play Store, you notice that people complain about the discrepancy between normal vision and thermal vision when superimposed on both. This story seemed rather strange to me, because if the person or the people who made the application could overlay 2 images, I could not see why they could not integrate a function that could shift the images. Especially since if the application was installed once, it's still a glaring problem! Except that people have not quibbled enough to the application. After 2 min, I discovered that there is a hidden function that can solve this problem! Just click on HTI, and there you can change the overlay!
The results
Example 1
Thermal image of a 3D print This thermal image is a thermal image of my 3D printer at the end of printing:
- you notice the heating tray that heats more on the right side than on the left side
- The ambient temperature is blue-green
- The 3D print is yellow because still a little hot
- The top of 3D printing that is super hot as it just ended
- Above the cross, the heating head of the 3D printer which is super hot, it's normal because it was at 200 degrees Celsius
Example 2
Another thermal image of a 3D print On this one, we notice the same details as the previous photo, but with a few more details:
- you notice the flow of air coming out of the fan at right angles as well as its path! This air is visible because a little warmer. Why is it a little warmer? It was when I saw this picture that I realized it, but if not, I think I would never have thought of it. The reason is simple: the heating tray sends hot air to the fan! So this one sends air at room temperature at first, but warmer air during 3D printing, making it less effective in cooling!
- The engine also heats up a bit
- The metal axis is also a little warmer due to friction
- The discrepancy we see is due that the photo was taken while the printer was in operation, so in motion.
Example 3
Thermal image of a wireless mouse For fun, does a wireless mouse heat up? The answer is yes and fairly uniformly for this model as can be seen.
Example 4
Thermal image of a handprint In some films have seen sequences where thermal cameras indicate a person's footprints. Is the camera accurate enough to show that? I didn't test with my feet, but I put my hand on a sheet 1 sec, and then I took a picture. You can clearly see the shape of the hand!
Example 5
Stick USB that heats up This image indicates that my USB stick heats up a lot (but it was no secret to me), but also the USB hub with a warmer area in the center, and as well as the cable that powers the usb hub!
Example 6
Thermal image half hidden by a handkerchief This image is to prove that a simple handkerchief can block thermal radiation. then see a person behind a wall…
The defect
There's one flaw: if your smartphone is in automatic change mode of your screen position in landscape-portrait mode, if this feature activates, the app reacts as if you had disconnected the sensor and put it back on. Except for this defect, I find this thermal sensor very interesting and very useful. It certainly does not have the accuracy and resolution that sensors 3 to 5 times more expensive, but these measurements are relatively correct and accurate. Link: https://fr.gearbest.com/testers—detectors/pp_009475122308.html?wid=1433363 