thermal sensitivity vs thermal accuracy


The FLIR E-series e60 has thermal sensitivity of 0.05 C while the FLIR i7 has thermal senstivity of 0.1 Celsius. Both have thermal accuracy of 2%.

Is the thermal accuracy over the entire range of the image or portion of the image (pixel wise)? If only part. Say there is a difference of 0.1 C in the portion, for example. 23.1 Celsius and 23.2 Celsius between 2 pixels. And if the the 2% accuracy is in different pixels or portions. Then it’s possible the 23.1 would become 25.1 C and the 23.2 C would become 21.2 C turning the 23.1 and 23.2 to bcome 25.1 and 21.2 C? Then thermal accuracy would smear any advantage of the thermal sensitivty. Unless it is uniform across all image portion? If so. What circuit parameter(s) exactly cause the thermal accuracy to change?

Those enegy audit. Can you really see difference between 0.1 C and 0.05C thermal sensitivity cameras?

Thermal sensitivity and thermal accuracy are different specifications. There is another factor that you need to be aware of which is spot size. An infrared imager (imaging radiometer) cannot accurately measure temperatures at the single sensor (pixel level)

Spot size defines the minimum size object that can be accurately measured with a given lens at a particular distance with a particular imager. Anything smaller than the spot size cannot be accurately measured, although it may be readily seen. The spot size will cover some number of sensors and is an important consideration when performing quantitative anaysis.

Thermal sensitivity specifies the minimum change in signal due to variation in incident radiation that the sensor can detect (i.e., how small a temperature variation can the imager see). The sensor can detect temperature variations in things that are too small for it to measure.

Each sensor in the array will have a different response curve to infrared radiation. Each cell in the array will vary in signal response from other cells around it for the same incident radiation. This is corrected through the camera firmware (set during the factory calibration process) and is periodically normalized through the NUC (non-uniformity correction) process, which corrects for drift. Most current imagers NUC automatically.

Basically, your imager will periodically flip a uniform temperature screen up in front of the sensor and readjust for the signal level of each pixel in the array so that it renders the same temperature across the whole array. Think of it like the mirror in an SLR camera. Every time your imager freezes and makes the familiar clicking noise, which is the screen flipping up in front of the sensor, it is going through the NUC process.

The NUC process is what eliminates the “smearing” that you refer to.

This is also the reason that your uncooled imager should be given time to warm-up and reach equilibrium in the environment in which you are using it. You may also notice improved image clarity an accuracy immediately after the NUC event.

This is but one of many reasons that thermography is not simply point and shoot. If you are doing energy audits you should be focused on the thermal patterns (qualitative analysis)

Yes you can see significant differences between imagers with different spacial resolutions and thermal sensitivities.

Uhm… just wondering. Decades ago. Digital camera only has 320x240 resolution, then 640x480 then 1Mpixel then 5Mpixel, now 15Mpixel. Thermal camera have 1Mpixel already. Given technological improvement. Do you think we would also have 10 megapixel (sensor wise) thermal camara in the future or is there a theoretical limit that give the maximum say 3Megapixel even 10,000 years into the future (akin to telescope not able to focus light at planck scale due to certain limit called the airy disc)? If so, what is the theoretical upper megapixel limit for the thermal ccd sensel?

I was wondering the same thing myself. WTF Chuck?


How did we manage to leap from a question involving an i7 imager to theoretic maximums for sensor arrays? If you’re working with an i7 now, I don’t think that you will be bumping up against the upper limits of the technology anytime too soon.

Your question might be better posed to someone involved in the design and engineering of detectors and imagers rather than on a user forum.

I think we told him to research before he selected a camera!!! :-0

?? :slight_smile:

1mp IR camera detectors (you can only buy the cores currently) are in the $80k range. Keep in mind that is just the core. Its video currently supports 720P. I would say at least another two years when 320x240 will become the norm with 640x480 coming down to the 320x240 prices within two years.

There are a lot of other integration’s that will be coming out before we see the 1mp cameras coming down in to the $20k range (where 620x480 is now). The biggest of which will be on board video storage and imagers that function more like a video camera that can take images rather than a camera that has a video out. I also wouldn’t be shocked to see on board Android integration (not just WiFi, the entire OS) or maybe some sort of proprietary tablet style camera.

The manufacturer that will take a quantum leap ahead of the others is the one that solves the problem that 90% of IR is reporting. There are ways to shorten that up with technology…some sort of auto tuning would rock, laser distance meter instead of laser pointer to calculate FOV automatically (among other things), auto emissivity (don’t ask how that would work) and further integration with other technologies for building science and PDM.

Another cool one would be to integrate the IR line scanner technology in to modern imagers for 3d imaging of moving parts. If anyone were to do something like this it would be Fluke since their parent company owns a company that makes IR line scanners, plus they have a huge industrial customer base already. Although who knows, it isn’t like FLIR doesn’t have the ability in the technology either.


Your right Rye. The wavelength of IR is longer than visible. Therefore, there is a maximum resolution that can be obtained with IR that is much lower than the resolution capable with visible light.
The smaller the wavelength, the better the resolution. Using your telescope example (slightly modified) - we can’t focus a microscope on individual molecules not because of the limits of magnifying lenses, but because we are bumping up against the resolution of light (limited by the wavelength). So we use a different technology with a much smaller wavelength of “light” in the form of a scanning electron microscope.

I don’t know what that effective upper limit of resolution would be for Infrared. But I’m sure someone could calculate it.


Where did you get the information that in 2 years 640x480 will get down to price of a 320x240 and the latter will be the norm?

I’m thinking now whether to transfer payment for a FLIR i7 with only 120x120 resolution. I plan to use it to see if aircondionining room is well insulated. Is this effective? Also mold water damage. At night. I always walk in the garden outside my house. I want the i7 to double as spotter of dangerous rats and snakes in the bushes. But snakes are said to be cold blooded. What is the temperature of a snake body with respect to the surrounding? Is it same temperature? Hope someone here can try to use their thermal camera to aim at snakes in the zoo. Pls. check the temperature as it would finally make me decide whether to get an i7 or wait for the 640x480 when it gets to the price of an e60 in 2 years. Thanks.

Once the snake has been solar loaded on a clear day, thermal capacitance will make it visible to you in the dark garden, as long as the snake cooperates and doesn’t spend his day in the shade or hide under a leaf in the dark.

You should wait for more advanced technology to come along. Imagers will be far more advanced 10 years from now. They will be so inexpensive that they will sell them as disposables.

hehe, how very true Chuck.

Rye, I am only guessing as to pricing…there is obviously no way of knowing this. I wasn’t really talking about the price of the E60, I should have clarified that. I think the 640x480 cams will be in the $10k to $15k range within two years. Which is ballpark pricing on the T300 to T400 currently. As a side note, 640x480 has more than held its pricing over the past two years vs what we have seen in the 320x240 and the sub 160x120 markets. Realistically speaking the 160x120 has actually held its pricing as well. The largest drop has been in cameras in the sub 160x120 range and the 320x240 range. This is mainly due to the Ti32 being almost 1/2 the price of other 320x240 imagers, when it released. The Fluke 160x120 cams are actually the same price they were two years ago, up until last month. FLIR has gone from the i/b 40 to the e40/e40bx which is $1k less or about 20%.

If you wait for something coming out, there will be something on that horizon, etc, etc, etc.

There is basically zero reason to wait for anything in technology for more than a month or two…even then that would drive you crazy over time.


Buying a high resolution imager in 2 years will put you 2 years behind your competition in experience!! Put a 120x120 in the hands of an experienced thermographer and a 320x240 imager in the hands of a beginner and see who finds the snake first!!:stuck_out_tongue:

I can’t beleive all this over an I7!?
That’s not even a “real” IR camera in this industry (IMHO).

Just go buy the thing and learn.
In 10 years you can throw it away and get something better (as many have).

I hope you don’t get bit by a rat or a snake while you wait for prices to come down. :mrgreen::mrgreen::mrgreen::mrgreen::mrgreen::mrgreen::mrgreen:

i7 is not even a real IR cam?

Oh no… I just made a telegraphic transfer payment to the manufacturer in Estonia and will get it in a few weeks.

Is there any thermal imaging course in Asia? Did you guys all learn it direct from a physical teacher or online course?

The i7 is useful enough to sample the 7-13 micro environment. Without this device, there is no way for you to know if a metal is below or above 100 Celsius at a distance… ain’t it. Also I think the i7 would be useful as a thermometer to measure forehead of people who may have fever. This is accurate enough that it could be used as replacement for a non-contact thermometer in hospital, right?


That depends if you consider that the +/- 2% will put you at 96.63F to 100.57F of human body temperature. 100.57F would be considered a fever for a person that is running at 98.6F.

Personally, I think all the border IR and fever IR is something to make the masses feel good about “things being taken care of”.

The others here are correct. At the very low end of the spectrum you should buy at least a FLIR E40/E40BX. If you can afford it, go up to the E50/E60. They are also correct in the fact that training is more valuable in the long run. Without the ability to adjust focus the I7 is not really considered any type of professional IR camera. They are really good for field guys of electrical companies or power companies that want to do some quick shots of panels, etc (just as an example)


As posted, you must decide the application and pick the camera.

There is nothing wrong with the I7 (for the intended purpose).

You are so all over the board on what you want to use and camera specs from $2k - $89k range, I am lost…

You can not do electrical/mechanical inspections with an I7 and go to the airport and prevent SARS Virus from entering your country…

How about Ebola? :mrgreen:


They just came out with a fart detection thermal imager. It has video capability too!!

Too bad I only hear this now that I have ordered the I7 from Estonia (all I7 are produced in Estonia). But I don’t like manual focus. I want to also use the i7 at streets or close parking to detect which cars are recently parked (heatness of the engine and hood) and I don’t want to keep focusing lens as it can lose time and make people notice. At home and office. I’d use the i7 to check on electrical panels to see which is breaker hotter and need replacement. Also to check on whether certain outlets and wires have enough thickness to be resistant to dangerous heat. Also inspecting what part of a room can cause heat making aircon lost efficiency. i7 is enough isn’t it. If not why not so I can maybe cancel my order at Estonia.

For me. The i7 is more of home use as well as field use. Admit it that a chechen rebel would benefit from even the i7. When in dark neightborhood. I want to use the i7 to quickly see if there are hidden people in the vicinity. And I don’t want to use manual focus and adjusting it slowly because in tactical situations. Time is of the essence.