Today I’d like to share a useful tool with you all – Thermal Imaging Camera for Smartphones. During circuit design or troubleshooting, Thermal Imaging Cameras can directly “SEE” the temperature distribution, and it’s easy to find and locate the insufficient heat accumulation and heat dissipation in circuit design. There are not many manufacturers of Smartphone Thermal Cameras on the market. I have used FLIR One Pro and Seek Compact Pro before, and last month I just got an InfiRay T3S. Let's make a comparative evaluation.

From Left to Right – FLIR One Pro，InfiRay T3S，Seek Compact Pro

1. Size, Weight and Material

a. Size

FLIR One Pro is the largest because it is equipped with a visible light camera. InfiRay T3S has the largest resolution with bigger lens. Then Seek Compact Pro is the smallest product among those three and its lens is also small.

Size Comparison of Thermal Imaging Cameras

b. Weight

All of the three products are light weighted.

• FLIR One Pro - 38g

• Seek Compact Pro - 15g

• InfiRay T3S - 40g

c. Material

Material of the shell is able to affect the product's strength, fall resistance, weight and electromagnetic radiation resistance.

• Seek Compact Pro - it feels like cheap plastic, and it's a kind of hard-shell plastic with average quality.

• InfiRay T3S - its shell is made of metal only, and that’s why it is the heaviest among those three. The shell of InfiRay T3S is oxidized and it feels comfortable. The all-metal shell can not only protect the internal circuit board when it is impacted, but also could shield electromagnetic wave. Therefore, in some strong electromagnetic environment, such as substation, InfiRay T3S can work normally without being affected.

• FLIR One Pro - it is made of synthetic resin. Feels soft and comfortable. It has a certain cushioning effect when falling. At the same time, FLIR One Pro does not have any lens exposed, which can protect the lens from being scratched or broken.

d. Lens.

The working wavelength of thermal imaging is 7-14µm. During this wavelength, the best lens material is definitely Germanium. While some producers also use less expensive synthetic materials. Through research and direct consulting with manufacturers, we learned that the lens materials are as follows:

• FLIR One Pro - Vulcanized Synthetic Materials

• Seek Compact Pro - Vulcanized Synthetic Materials

• InfiRay T3S – Germanium

Lens Size - FLIR One Pro, Seek Compact Pro, InfiRay T3S

For the infrared band, Germanium is a natural and excellent high transmittance material. Its transmittance is more than 95%. With the coating, the overall transmittance can reach more than 99%. While among synthetic materials, only selenium sulfide or zinc sulfide can pass through the infrared band. The transmittance of these materials is about 90%, and with coating, it can only reach about 95%. The higher the transmittance of the material, the clearer and cleaner the lens image can be. At the same time, because the infrared energy loss is small, the temperature measurement accuracy will be increased.

2. Image Quality

The basic functions of Smartphone Thermal Cameras are imaging and temperature measurement.

Resolutions of the three models are:

• FLIR One Pro - 160x120, with visible light camera 1440x1080 pixels

• Seek Compact Pro - 320x240

• InfiRay T3S     - 384x288

Let’s compare their image quality in below.

a. Nearby Static Objects

Start with FLIR One Pro, the overall image quality has been upgraded to a certain level with visible light images superimposed. For nearby static objects, the overlapping parts of infrared image and visible image can still match basically.

The resolution of Seek Compact Pro is 320 x 240 and its image quality looks almost the same as FLIR One Pro’s 160 x 120 resolution. Moreover, it can only see the hot target, and the reflected image of the floor is very fuzzy and almost invisible.

The images taken by InfiRay T3S have the highest resolution of 384 x 288. Sharp edges, clear details, sufficient sense of hierarchy, and even the images reflected from the ground are very clear.

b. Nearby Portrait

Image processing ability of FLIR One Pro is good. Compared with Seek Compact Pro, FLIR One Pro has lower resolution, but better image quality. Due to the complexity of the shooting target and the clutter of the background, the point-to-point overlap of the visible light superposition part can not be achieved, and the superposition effect needs to be strengthened.

Take a look at those images taken by Seek Compact Pro, it feels like a "pit" with white on the outside and black on the inside everywhere. And the hair and background are almost mixed in Seek’s images.

While images from InfiRay T3S is much clearer. The hair and facial features of the model are very clear, and even the fat and muscle on her face can be seen clearly.

c. Medium Range Image

Above images are all taken from twenty meters away.

The image quality of FLIR One Pro is good at close range, however when shooting a 1.7 meters high model from twenty meters away, it is difficult to distinguish the human body from the floor reflections. The superposition gap between visible and infrared images is becoming larger and larger from long distance.

With Seek Compact Pro, although the overall image still looks rough, and the "big pit" with white outside and black inside is still there, the details of the human body are better than those images taken by FLIR One Pro, which can distinguish the body and the reflection of the model.

InfiRay T3S’ image is very clean, showing model’s head, arms, even palms, feet and reflections of the human body.

d. Long Range Image

FLIR One Pro's infrared image is totally a blur without visible light camera overlap. While with visible light images, the effect of floors and windows is better. However with the increase of distance, the difference between visible and infrared images is becoming larger and larger. Thus in general, with the increase of visible light, the image recognition is much higher.

The "big pit" of Seek Compact Pro is finally out of sight in those images. Although the floors and windows can be distinguished, the trees and street lamps on the road in front of the building can not be seen.

Those images taken by InfiRay T3S can not only clearly distinguish the floor and windows, but also the logo of the open windows and the roof. Most of all, the street lights and signs in front of the building are clear as well. To be honest, if you only look at the front three pictures, you can't tell what is in front of the building.

It can be seen from the previous images that InfiRay T3S has the highest resolution. Its image is delicate, clear and layered. Even without the visible light image superposition like FLIR One Pro, the image edge is very sharp. Especially when shooting nearby static target, the small lines and logo on the main target are very clear.

3. Temperature Measurement

• FLIR One Pro: 20 - 400℃， accuracy ±3℃ or ±5%

• Seek Compact Pro: 40 - 330℃, accuracy unknown.

• InfiRay T3S    : 20 - 120℃, accuracy ±2℃ or ±2%

It can be seen from the above data that although the temperature measurement range of InfiRay T3S is not the widest, the temperature measurement accuracy is the most accurate.

a. Body Temperature Measurement

• FLIR One Pro - 35.5℃

• Seek Compact Pro - 33℃

• InfiRay T3S - 36.13℃

Generally speaking, the temperature measured by FLIR One Pro and InfiRay T3S is close to the normal forehead temperature range (35 ~ 37 ℃), while the temperature measured by Seek Compact Pro is quiet off. Even though the temperature measurement accuracy of the Smartphone Thermal Cameras is lower than the thermometer, its advantage is that the temperature measurement speed is faster. You are able to get the temperature instantly by checking the forhead.

b. PCBA Temperature Measurement

FLIR One Pro, with the help of visible overlap, can see positions of components, however the problem is that the thermal and visible images do not match very well.

It’s kind of hard to find positions of each component with Seek Compact Pro. Just could barely see PCBA itself.

InfiRay T3S is able to provide a clear image and it’s easy to locate the component with the highest temperature.

c. Parameter Settings

For temperature measurement, the setting of parameters has the greatest influence on its accuracy. All three products have emissivity settings. Both FLIR One Pro and Seek Compact Pro come up with several settings which is simple and easy to understand, like Sub Light, Semi Matte, Semi Highlight and Highlight. However expert users may not be able to set emissivity for specific material to get accurate result. InfiRay T3S has temperature measurement parameters such as emissivity, ambient temperature, humidity, distance, reflection temperature, temperature correction and etc. Although it is troublesome for primary users to understand and set these parameters, if they are set well, hardware engineers can get the most accurate temperature. The reflection temperature is a very important parameter and it can accurately measure the temperature of the peripheral device beside the high temperature device.

4. Battery Lifetime

FLIR One Pro equipped with battery that needs to be charged before use. Seek Compact Pro and InfiRay T3S are powered by smartphones through USB connection.

The battery lifetime of FLIR One Pro is very short. It only lasted about thirty minutes when I used it. When ambient temperature is lower, the battery lifetime is even shorter.

5. Conclusion

Considering materials, image quality, temperature measurement accuracy, InfiRay T3S is the best and highly recommended. (All rights reserved. Please indicate the source if repost)