Flir Thermal Camera Question

[bostonman]

I have a Flir Thermal Camera - Model TG267 that I bought used.

I'm new to thermal imaging and expected the image to show a more distinguishable separation of heat.

As an example, my boiler has several routes of copper pipe along with a few gauges. The copper pipe and fittings are extremely hot and the face of the gauges are quite cool (especially compared to the hot copper pipes).

When I aim the camera in this area, some of the copper pipe is blue, some is red, and the gauges show all red. Since all the copper pipe is hot (probably >120 degrees F), I expected to see red lines in all the directions of the pipes and some blue spots where the gauges are since the faces are much cooler than the copper pipe (and gauge fittings).

Initially I suspected the cold concrete floor is throwing off the camera, so I aimed parallel to the floor and still got similar results.

When I aim the camera at my concrete foundation walls and windows, I see blue for the window (it's currently around 45 degrees F outside), but the walls show a shade of red. I expected everything to be blue since the windows and walls should all be quite cool.

I tried changing the image to rainbow and lava, but got similar results.

Am I using the camera wrong?

[bostonman]

I've been tinkering with this camera and still have some questions.

Attached are four pictures. The two named 'Rainbow Color 1 and 2' were similar except I moved the camera a bit more to the right. It's a picture of my baseboard and window.

As it shows, a bit more heat is shown rising on the wall in one picture versus the other. This is what I'm confused over, why do things change when I either change angles or change which objects are in the picture?

The other two are the same picture, just two different modes. In the one named 'Iron Color' it shows more red (i.e. heat rising from the baseboard) than the one named 'Rainbow Color'.

Am I just interpreting the images incorrectly?

[Bud]

The camera is trying to auto range and give you the best contrast picture. It detects the coldest and hottest spots in a scene and stretches the palette to fit in the temperature span. As you change the scene even slightly, the span will be slightly different  which is enough to re-fit the palette, changing the color of a same spot from the previous scene. In order to avoid this and get consistently mapped color you need to disable auto range (enable manual range). This will lock the mapping but may not give you best contrast picture, you will need to manually adjust lower and upper bounds of the temperature range.
Not all cameras have manual range, typically mire expensive cameras do.

As to different colors in two different palettes- you cant compare that, each palette has its own mapping of temperature to color.

[bostonman]

This makes a bit more sense.

Looking at my manual, I don't see a way to turn off auto range.

Some images appear to be spot on with what I'd expect for a thermal image, but then other images baffle me. Sometimes an area is cold, yet, the camera shows some red.

Although I haven't dug into this much, my assumption is that an area is red with respect to a cold area instead of it being red because it's extremely hot.

I still don't understand why the pips and gauges on my boiler show blue on areas that should be red hot. My thought is the cold coming off the basement floor is interfering. Also, areas in my basement (non heated) such as my workbench show red areas indicated warmth, but most areas should be about 60 degrees F.

The things that have fascinated me: if I press on an area with my hand, the heat that is transferred from my hand to the object remains warm for quite some time. I tried this on my where I placed the palm of my hand on the wall and my hand image remained for a good three-minutes.

The way heat dissipates from my baseboards and stove is amazing. I think it's so cool to see the peaks and valleys of heat in an area.

[Bud]

Regarding pipes and gauges, if they are bare metallic, this may throw thermal cameras off. Have a read on materials emissivity. For accurate measurements of a material you need to offset the camera with values specific to particular material. This works as a correction coefficient. Again cheap cameras do not have material emissivity setting.
To test this you can place a strip of black electric tape over the pipe and look again. The part covered with tape will show correct temperature (less some loss through the tape). Or you can paint the bare pipe for an experiment.

[Gyro]

...
I still don't understand why the pips and gauges on my boiler show blue on areas that should be red hot. My thought is the cold coming off the basement floor is interfering. Also, areas in my basement (non heated) such as my workbench show red areas indicated warmth, but most areas should be about 60 degrees F.
...

Specifically, the glass on the faces of the gauges is reflective to LWIR. Point your camera at a window and all you will see is your own reflection, not what is on the other side. Most likely you are seeing the reflection of the basement floor. Likewise any Chrome, it has very low thermal emissivity. The bits of tape method is the way to go.

EDIT: Time to do some reading. Iirc, there are some useful documents on the Flir website. Fraser has probably posted some useful stuff on here too if you search.

[JXstaystonight]

One thing to keep in mind is that thermal cameras often struggle with objects that have low emissivity, such as shiny metal or reflective surfaces (like the gauges on your boiler). The reflection from those surfaces can skew the readings, making them appear hotter or colder than they actually are.

Another factor to consider is the effect of ambient temperature on your readings. If your basement is cooler, the camera might show more red (indicating warmth) in areas that are only slightly warmer than the surroundings. This can be misleading, especially if you're comparing small temperature differences.

[bostonman]

If your basement is cooler, the camera might show more red (indicating warmth) in areas that are only slightly warmer than the surroundings.

I haven't read much about thermal imaging, but I assumed this was the case.

Initially I thought "red" indicated a specific temperature range, but, due to experimenting, it seems red indicates a warmer area.

My basement is probably 60 degrees at the moment. If I've understood things correctly (between this thread and experimenting), an area that may be 70 degrees will show red since it's hotter than the ambient area. Yet, if I looked at my stove when it's on, it will show red with the surrounding area blue/yellow to show the cooler area.

[Berni]

Good thermal cameras allow you to set a manual range, that way red or blue is a specific temperature.

Also most shiny objects are not going to be measured correctly by any thermal camera. They typically have a low emissivity, this means they radiate very little IR. This long wavelength IR light is what the camera measures. In theory you can compensate by setting the exact emissivity in a good camera, but in practice it does not work. These shiny low emissivity surfaces also are great mirrors for IR, so they will reflect IR light from other hot objects in the room, so the temperature measurement will be wrong.

The solution for low emissivity is to cover the object something with a high emissivity. One way is to paint it, black permanent markers work well for that. Other way is to stick something to the surface, my favorite for that is Kapton/Polyamide tape (good emisivity and has a wide temperature range), but something like masking tape might work well too.

Also watch out that long wave IR has a very long wavelength, so a lot of mat finish metal objects still look like a perfectly smooth mirror. These IR photons are such long wavelength that they don't see the fine surface features.

[bostonman]

my favorite for that is Kapton/Polyamide tape (good emisivity and has a wide temperature range),

This isn't too reflective for the camera?

The explanations make much more sense. I had a feeling part of the issue was the quality of the camera, but I didn't realize metal and shiny objects would cause issues.

I assumed a mirror would cause issues, but expected to distinguish more when I aimed it at the boiler pipes. Hopefully over the weekend I'll have time to experiment more by adding tape to see how it affects the image.

[Berni]

Kapton has a emisivity of 0.96 so it is very close to being a black body. Thermal cameras typically use a default emissivity of 0.95 since that's about what most IR opaque materials are.

You have to remember that these cameras only see the world in long wavelength IR, while we only see the world in visible light. Something being shiny or transparent to visible light does not necessarily make it act the same in IR. For example LWIR does not go trough normal soda lime glass at all. Quite a few transparent plastics are also opaque to LWIR, this is why CO2 IR lasers cut them so nicely. While some plastics are reasonably transparent to it, for example you can't see trough black garbage bags, but a thermal camera can see right trough it like the bag is transparent. A good cheap "thermal window" is saran wrap, it can be used to replace the door on a piece of electronics to get accurate thermals while still being able to see trough the door with a thermal camera (and visually too since that plastic happens to also be transparent to visible light)

Some gasses are also opaque to LWIR like CO2 or methane. So if you have a CO2 gas leak, you won't see it visually, but on a thermal camera it will show up as a black cloud of smoke. This is also why CO2 is a greenhouse gas, it prevents earth from radiating out into the cold space in LWIR, so it makes out planet get hotter.

[bostonman]

Thermal cameras typically use a default emissivity of 0.95 since that's about what most IR opaque materials are.

I'm uncertain I understand exactly what this means. My camera apparently isn't fancy enough to have the settings mentioned in this thread, so we can rule out making changes to it.

Does this mean it's designed to only "see" objects that have emissivity of 0.95? I assumed thermal cameras just saw what they are capable of seeing, but it could be changed?

I need to better understand emissivity. I did some quick reading, but the concepts didn't quite sink in to apply it to the camera.

Earlier I played with the camera and was amazed to see that it saw my hand inside a black Hefty trash bag. I also looked at my boiler pipes (again) and the copper must have a poor emissivity (or too reflective) as it didn't show hot throughout the pipes. It does show heat on the grey colored pipes existing the boiler (they are not black iron, but grey..... grey threaded iron?) to a degree. The brass bleeder valve connected to the grey threaded iron doesn't show as well.

I applied black electrical tape to the copper pipe and the sides showed as red while the center part showed white. Looking at the 'rainbow' color range on the camera, white is the hottest, so this makes sense.

[IR_Geek]

I'm going to try and not 'geek out' to much.   You are running into one of the rabbit holes of infrared imaging / radiometric measurements.    EVERYTHING above absolute zero emits radiation ... the walls, floor, people, trees, etc...  The key is having an instrument capable of seeing it or in reality  the temperature difference.   One of the main metrics for an infrared camera is NETD (noise equivalent temperature difference).   I personally can't stand that term as it doesn't really reveal an infrared imagers true performance.   However, for the case of understanding emission it will work.   If everything in your scene is the same exact temperature then even the most expensive ($100K's) infrared camera wouldn't be able to see anything.  That's where emissivity is an excellent 'trick'.  There are two terms that you need to understand.   Apparent Temperature and Absolute Temperature.     Apparent temperature is what all infrared imagers see unless you account for the other parts from the equation ... 1 = T + R + E  ...  T = transmission, R = reflection, E = emission.     You can get to the absolute temperature once you account for the reflection, transmission, and emissivty. 

Take the copper pipe you were looking at.   If you want the absolute temperature, the most accurate would be a thermocouple.   However you can not plaster the entire pipe with thermocouples.   To get an accurate reading you need to know the emissivty of the pipe and the reflections.  In this case the transmission through the pipe would be 0.   The emissivity could vary from shiny copper (~0.03) up to oxidized copper (~0.74).   That would then mean the reflection is then calculated as ( R = 1 - E ).    Now you have to consider all the other objects in the room that could be emitting and then therefore reflecting off the pipe.     

Rabbit hole #2 ... spectral content of sensor, optics, and material.
Rabbit hole #3 ... the atmospheric transmission losses between the object and sensor.

This is why there is such a difference between a thermographic collection and a radiometric collection.   Thermography takes a lot of shortcuts and assumptions.  Nothing wrong with that but it is sometimes misused which can lead to erroneous results.

You are on the right path and there are many free sources of information.    I highly suggest the older books (PDF's) and take much of what you see on websites with a healthy dose of skepticism.    Even FLIR and FLUKE gloss over a lot of things.

[bostonman]

Wow, you seem to know your IR.

The basic concepts make sense and something that I assumed in the beginning that reflective surfaces affect the image. I thought it would be more mirrors and windows, however, I was able to see a a perfect blue rectangle when I shined it on my basement casement windows.

Most likely I'll conduct more research. This camera was a bit more of a toy than a need for a project, however, going forward, maybe I'll use it for looking at circuits that I build. At the moment I tinker at random times which helps me learn so going forward I'll have a better understanding at interpreting images on more important stuff than measuring 170 degrees F on copper pipe.

So if I could set the emissivity on my camera to ~0.03, then I'd be able to see the heat coming off the copper pipe without the need for black electrical tape or Kapton tape?

[Berni]

So if I could set the emissivity on my camera to ~0.03, then I'd be able to see the heat coming off the copper pipe without the need for black electrical tape or Kapton tape?

No.
See my previous post.

Yes if something has a emissivity of say 0.1 that means it only emits 10% of thermal radiation as compared to a black body (it is what defines the emissivity of 1.0). So if the camera compensates by boosting the IR light signal by 10x to get those 10% to become the 100% of a black body you will then get the correct temperature... only if ALL these cases are true:
- Room is completely uniform in temperature
- Thermal cameras ambient temperature sensor is the same temperature as the uniform room
- No other warm objects present in the room (this includes your warm human body, so step out of the room and operate it remotely)
- The object you are measuring is completely clean of any dirt (as the dirt might have a different emissivity)

As you might notice, all of these conditions are actually pretty difficult to guarantee in real life use cases, especially all of them at the same time. This is because low emissivity objects are also great mirrors for LWIR light, hence they reflect thermal energy from other warm objects in the room (including yourself and your warm thermal camera) so with more IR light it looks like it is hotter than it is, these is no way for the camera to tell these apart, hence why you need the conditions listed above. It is the laws of physics that pose this limitation, not the camera. Same for those IR thermometers

So in the end it is easier to just put a piece of tape on it.
Besides if you want accurate temperature measurements there is no beating sticking an actual probe on the object.

[bostonman]

Besides if you want accurate temperature measurements there is no beating sticking an actual probe on the object.

I fully agree with this statement. My model camera is low end (or believe to be), so I wasn't expecting much, however, it is better than I anticipated.

Initially I thought with a 160 degree F pipe and a surrounding temperature of approximately 60 degrees F (along with a cold concrete floor), the camera would show everything with perfect color separation.

Your explanations have helped understand why this isn't the case.

I guess some confusion remains with how do I know which objects have low or high emissivity?

My heater baseboards (hot water heat) were painted white at one time. When I aim the camera on them, I see a horizontal red line indicating the heat in that area and then uneven vertical (what appear to be) flames rising up from them; obviously the heat rising up the wall.

How do I know if what I'm seeing is real because the baseboards can be reflective to the IR.

[timeandfrequency]

An abstract about the influence of emissitivity.

I guess some confusion remains with how do I know which objects have low or high emissitivity?

Emissitivity table found in Yumpu

[bostonman]

The table link seems to be broken.

[Bud]

I guess some confusion remains with how do I know which objects have low or high emissivity?

Higher end thermal cameras have a setting where you select the material you intend to measure, e.g brick, concrete, glass, particular metal, etc. The camera then applies proper emissivity correction.

[Berni]

How do I know if what I'm seeing is real because the baseboards can be reflective to the IR.

Best way is to hold the camera steady and then wave your hand around the object of interest. If it is a low emissivity surface then you will see the reflections of your warm hand moving around on the surface of the object. If nothing appears to move, then it is a high emissivity surface.

This connection between low emissivity and being a mirror also goes back to physics. The reason why objects in the same room all equalize to the same temperature as the room is the fact that all warm objects around room temp radiate LWIR. If a object is colder than the room then it gets more LWIR light shining on it than it is emitting, hence it warms up, opposite for hot objects, they radiate more than they get radiated on, so they loose energy in total. Now if you had a material that radiates LWIR with an emissivity of 1.0 while also being a mirror to LWIR, then that object would radiate its energy out, while bouncing away any LWIR that hits it. As a result this object would start getting colder than the room it is in by simply being there. This violates the rules of thermodynamics, since you could apply this object to the cold end of a heat engine (like say a Stirling engine) and get infinite free energy. Hence you will never find a low emissivity material that doesn't look shiny in some way.

There are some ways to cheat this rule to get free cooling anyway. For example there are materials that can be below ambient while in direct sunlight. They do this by being very reflective to visible light while being a black body to LWIR light. Sunlight does not contain much LWIR, while outer space is basically a black hole for LWIR as the photons just keep going without ever bouncing back. Hence when such a material is exposed to a clear sky it can radiate away LWIR into outer space and not have it come back. You can see this effect yourself if you point your thermal camera at the sky, it will look very cold.

You can't rely on tables from the internet to tell you the emissivity as that only applies to perfectly clean and uniform surfaces. Most real life surfaces are dirty or corroded and that dirt might have a significantly different emissivity.

[timeandfrequency]

The table link seems to be broken.

Strange : the link opens without any problem on my computer 
Here's another one : https://www.omegaengineering.cn/temperature/Z/pdf/z088-089.pdf

[bostonman]

You can't rely on tables from the internet to tell you the emissivity as that only applies to perfectly clean and uniform surfaces. Most real life surfaces are dirty or corroded and that dirt might have a significantly different emissivity.

Although I have very little understanding, I feel this is an accurate statement. Upon looking at tables, I questioned which category my painted baseboard covers fall into, so I realized the tables are not completely applicable.

This thread has taught me that thermal cameras and emissivity is complicated. Prior, I thought you just aim the camera and everything in the room will show as colors that accurately provide temperature regardless of material.

Aiming the camera on surfaces and getting low/high emissivity is a bit clearer for me now. One thing I'm curious about is placing my hand in a black (Hefty) trash bag and the camera seeing it. I even put space between the bag and my hand, and the camera still saw it.

Black tape on something hot (such as copper pipes) make sense because (or at least I thought) the tape becomes the "same" temperature as the copper pipe, so you're measuring the tape; but maybe it's measuring the pipe since the bag covering my hand is measuring my hand.

[IR_Geek]

This thread has taught me that thermal cameras and emissivity is complicated. Prior, I thought you just aim the camera and everything in the room will show as colors that accurately provide temperature regardless of material.

This is one of the hardest things to get people to understand.     I can't count the times I've seen videos on YouTube or TV (ghost hunters makes me want to bang my head against a wall!) that completly mis-represent what "Infrared" can actually do.

As for your question about the black hefty bag:   It is transparent in the 7-14um wavelength range that handheld uncooled cameras operate in.   Think of it like a piece of glass that is transparent in visible (0.4-0.7um).   

On the topic of black electrical tape on an item to measure:   It's such a small thermal mass that it will quickly become the same temperature as the object you put it on.   However, since it has a high emmissivity it will radiate that temperature instead of reflecting other temperatures in the room.     A good way to understand that is to put a piece of tape on the object and another piece on some cardboard.   Put the taped cardboard in the same image and compare.

[Berni]

Aiming the camera on surfaces and getting low/high emissivity is a bit clearer for me now. One thing I'm curious about is placing my hand in a black (Hefty) trash bag and the camera seeing it. I even put space between the bag and my hand, and the camera still saw it.

A black body object is not necessarily visually black!

You have to understand that thermal cameras operate in a completely different part of the electromagnetic spectrum as human eyes do. At the same time the optical properties of a material is a continuous function that goes from radio waves all the way to gamma rays. Our human eyes can only see the narrow part in the middle called visible light.

Just because a material is reflective at one wavelength says nothing about it being reflective at another wavelength. So it is perfectly possible to make a paint that looks white to our eyes, but looks black under IR light. Or the opposite a black paint that is actually very reflective under IR light.

A good example of this is the black IR windows on TVs and TV remotes, or also seen on IR LEDs or IR phototransistors. It is a plastic with a dye in it that absorbs visible light, but is completely transparent to IR light. Similarly Coca Cola looks black to our eyes, but it looks as transparent as water in IR (you can try shining a TV remote at a camera trough a bottle of coke). Note that this is short wavelength IR of around 900nm that IR LEDs can produce. Thermal radiation is even longer wavelength IR at around 10000nm, hence something transparent to short wavelength IR is not necessarily transparent to long wavelength IR. For example water or common window glass is transparent to 900nm IR (so your TV remote works trough it) but LWIR does not go trough it at all, so a thermal camera can't see trough a glass window at all. If we take this even further, going down to a 1 000 000 000 nm wavelength you get radio waves, some materials pass radio waves just fine, some don't, and it has nothing to do if the material is looks black visually.

So your black garbage bag to LWIR likely looks as transparent as a transparent plastic bag.

So you can't rely on your human vision to tell things apart as they cover only a small range of the spectrum. Heck even within that spectrum they have flaws as we can only see in in R G B. So to our eyes yellow light looks identical to a mix of red and green light. There are some humans with a genetic mutation that gives them a 4th color receptor, these people can tell apart some colors that look identical to everyone else.

[bostonman]

If we take this even further, going down to a 1 000 000 000 nm wavelength you get radio waves, some materials pass radio waves just fine, some don't, and it has nothing to do if the material is looks black visually.

I'm going down a rabbit hole and going to ask a really silly question.

Does a camera exist that can see radio waves?

That would be pretty cool.