Specification of a thermal camera for PCB repairs - some thoughts

[Fraser]

I have just been using one of my thermal cameras to repair a laptop and it occurred to me that it may be useful to start a thread discussing the minimum specification of thermal camera that is practical for use in repairing modern PCB’s. I will provide my view on the matter but welcome others participation as newbies to thermal imaging may be uncertain of what is required for PCB repair work.

Before we get into specifications etc, it is worth stating what a thermal camera offers by way of PCB repair and disagnostics.

The thermal camera can only show the user temperature information, be it a spot temperature or a temperature differential. As such it is well suited to spotting parts of a PCB that exhibit one of the following symptoms:

1. A component or area on a PCB that is running hotter than expected (e.g. a regulator with a shorted output)
2. A component or area on a PCB that is running cooler than expected (e.g. a circuit that has lost its power supply so not working)
3. A component that is pulsing on and off when it is supposed to be constantly on (commonly called hiccuping due to overload or the opening and closing of a Polyfuse due to overload)
4. Low or no thermal activity in a microprocessor indicating a potential “SLEEP”,  “HALT” or “RESET” state.
5. PCB tracks becoming thermally visible due to high current flow through them (often caused by a shorted component or track “down stream”)
6  Capacitors becoming hot (Often a sign that the capacitor is failing or in distress)
7. Excessive temperatures found on a heat-sink (either due to an inadequate heatsink or a fault causing excess dissipation from an associated component.
8. Excessive heat build up within an equipment case (often caused by inadequate ventilation, obstruction of air flow or a failing fan)
9. Components running unexpectedly hot. (May be due to designer underrating of component or a fault causing higher than normal current flow through the component)
10. Batteries becoming unexpectedly hot during charging (potential battery issue or a failure in the charging circuit - where Li-Ion is involved, this is serious !)
11. Heat visible from a connector (this can be evidence of an underrated connector, for the current it is carrying, or a connection with a higher resistance than normal due to contamination or corrosion. Some GPU PCB’s suffer from this on power connectors.)
12. Part of a circuit warm when it should be switched off (this can indicate failure in a power rail control, such as a series MOSFET short. This can lead to battery operated equipment discharging batteries even when switched off.

Well that will do for my list of potential issues that a thermal camera may assist in diagnosing. There are bound to be other examples so feel free to share your experience here. My following posts will discuss thermal cameras and their specifications.

Fraser

[Fraser]

Thermal Camera specifications and how they effect use for PCB thermography…..

As detailed above, a thermal imaging camera offers the user an insight into the thermal domain of a PCB or piece of equipment. Such insight can greatly aid diagnostics and provides a better understanding of electrical activity within a system. The thermal camera only provides information on thermal energy however and it is for the user to interpret what it shows on its display. This can be easy or challenging to the user, dependant upon experience and the nature of the fault. For a user to be able to interpret the thermal domain of a device under test (DUT) the thermal camera needs to be of adequate performance to both detect and display a thermal anomaly, if present. This post will detail the effect of specifications on a cameras usability for PCB repair work. It is not a discussion of the best camera specifications or best “bang for buck”. That is for the reader to consider. I offer only an insight into the effect of certain specifications on a thermal cameras capabilities.

So on with the specifications of interest to us in PCB thermal profiling and repair……..

RESOLUTION

I have placed this specification at the top for good reason. It is often used by manufacturers marketing teams to try and impress the potential purchaser of a thermal camera. There is no argument against “more pixels is better” in the world of thermal imaging as cameras generally have relatively low resolution compared to modern visible light digital cameras. The problem is, more pixels = more expensive and the increase in price can be exponential with resolution. Hence this thread discusses what you actually need for PCB work rather than what you think you need or want ? It should really be stated that a very badly designed higher resolution camera may offer poorer imaging performance than a well designed lower resolution camera. There is more to thermal imaging camera performance than purely pixel count.

So what resolutions of thermal imaging camera are common in the marketplace and what are my thoughts on each ? See below:

a) 16x16 pixels (such as the IRISYS Redeye 6)

With only 16 x 16 pixels present on the sensor array, the ability of the camera to resolve much detail on a PCB will be severely limited. The manufacturer will likely employ interpolation to increase the presented image to something more reasonable, such as 128 x 128 pixels. It should be understood that interpolation does not improve the RAW resolution so cannot really pull more detail out of the original data from the sensor array. I personally consider this resolution too low for PCB work as the image provides little to no thermal scene context for interpretation by the user.

b) 32x32 pixels and 49x49 pixels (for example the IRISYS Redeye series)

As stated previously, low resolution thermal sensor arrays can provide a thermal image but they normally lack the detail needed by a user for context within the thermal scene that is a PCB. Whilst 32x32 and 49x49 pixels is significantly better than the lower resolution sensor arrays, it remains too low for many PCB thermal analysis tasks and far better options exist for not a lot more investment by the user.

c) 80x60 pixels (for example the FLIR Lepton 2 core)

In the past, 80x60 pixel sensor arrays were considered a serious entry point into thermal imaging that was actually useful. Interpolation was still employed to make the displayed image more acceptable to the user but in this case the amount of RAW thermal data from the sensor array was adequate for some understanding of the thermal scene and interpretation by the user. The FLIR Lepton 2 was a very popular thermal imaging core that proved 80x60 pixels was a viable resolution for many non-demanding thermal imaging tasks. Such a low resolution is still far from optimum for creating easily interpreted thermal images, but when combined with a visible light camera scene overlay (MSX or Thermal Fusion) the context of the scene became clearer to the user. Sadly the use of a visible light image overlay on such a low resolution sensor array image can be difficult when working on a PCB at close range due to parallax error. There is no doubt in my mind that a 80x60 pixel thermal camera may be used for diagnostics on a PCB, but it is more challenging than when using higher resolution cameras as the exact source of thermal energy is not always obvious. Such low resolution cameras also need a suitable lens system to improve their usefulness in PCB work and this will be discussed later.

d) 96x96 pixels (HikMicro produce such a sensor array)

This resolution is a relatively recent addition to the market and is found in some low cost thermal cameras. It is common for cameras using this sensor array to interpolate the RAW data and state a 240x240 resolution in the specification. This is an old trick from the early days of thermal cameras and if the use of interpolation is not made clear to the user, it is a deceptive practice. Some manufacturers employ both Interpolation and “Super Resolution” to the image presented to the user. It should be understood that true Super Resolution is a technique that makes use of the natural hand shake of the user. It is rendered ineffective if the camera is rigidly mounted on a stand or tripod. Such a camera would then rely on the interpolation image enhancement only. 96x96 pixels is in the same category as 80x60 in my opinion. It can be used fir PCB thermal analysis, but if the super resolution mode is not effective, the displayed image remains relatively low resolution for the user to interpret. Such a camera would certainly be useable for PCB work though.

e) 120x90 pixels (common in many entry level budget cameras that use the Guide Sensmart TIMO imaging core)

Another relatively recent resolution sensor array offers 120x90 pixels and this can produce pretty decent images when interpolation is also applied to the thermal scene data. This resolution is most definitely useable for PCB thermal imaging when searching for thermal anomalies such as previously detailed. Whilst the images will lack fine detail, they are adequate and may be interpreted without too much difficulty. This is especially so if the lens system is suited to PCB work. (Close focus lenses) in my opinion, 120x90 pixels is the lowest resolution that I would recommend for PCB work. It is by no means optimal, but having used it myself with good success, this resolution is worth considering if working to a tight budget.

f) 160x120 pixels (this resolution has been around for many years with many imaging cores available)

The 160x120 pixel resolution is well known to those of us who have been involved in thermal imaging for the past three decades It used to be the popular “entry point” for microbolometer based thermal imaging systems. This resolution, when used in a well designed camera system, offers decent thermal imaging that is most definitely adequate for PCB repair work. I have used this resolution for PCB repair work many times with reasonable ease. Once again the ease of use is often dictated by the optics of the system as this effects the resolvable detail, as will be discussed later.

g) 256x192 pixels (very common on modern thermal camera releases from Asia)

The 256x192 pixel sensor array is a relatively new release to the market and this is because China started mass production of microbolometer sensor arrays at this resolution. The choice of resolution was likely the result of balancing resolution, resultant die size, production yield and cost. As China has become a powerful influence on the budget thermal imaging equipment marketplace, it is no surprise that 256x192 pixel thermal cameras are now very common. In my opinion, this resolution is an excellent choice for PCB repair work as it appears to provide the best balance of resolution and cost for some very useable thermal imaging. I have no hesitation in recommending a decent 256x192 pixel thermal camera for PCB work. Lens choice must also be considered but this will be covered later.

h) 320x240 pixels (this is a “Standard Resolution” in the thermal imaging industry that has been around for decades)

320x240 pixels is QVGA and has met the demanding needs of Industry, Fire fighters and the military for many years. In recent years we have seen QVGA+ in the form of 336x256 pixels and 400x300 pixels as enhancements on the standard QVGA resolution. At 320x240 pixels the thermal scene is easily interpreted by the user due to the scene detail captured providing good context. This is where the “if you can afford it” recommendation comes in. I personally like to use thermal cameras that are QVGA or better resolution as the imagery is a pleasure to interpret and decent cameras produce crisp, low noise imagery at this resolution. Sadly the increased size of the microbolometer die over a 256x192 pixel microbolometer, combined with lower production numbers, means a QVGA thermal camera may cost significantly more than a 256x192 pixel mass produced model. For PCB thermal analysis, QVGA and QVGA+ is a joy to use but appropriate optics are still required.

i) 640x480 pixels (often thought of as a Gold Standard in thermal imaging and less common due to high cost)

Whilst it is true that 640x480 pixel imaging sensor arrays offer excellent thermal imagery for the user, it often comes at high cost. The relatively low production numbers of the VGA sensor array and associated cameras tends to keep retail prices high. As such, a user needs to determine whether the higher resolution and associated cost is truly justified in their use case. Whilst the military may have good reason to need a VGA sensor array in their long range thermal targeting systems, do you really need such for just PCB repair work ? I would say no. If your budget is such that a VGA PCB thermal analysis camera may be easily purchased, that is great and you will like the imagery that such produces….. provided the optics also suit the task at hand ! More on that later. VGA thermal cameras used to be rare indeed. With advancements in production techniques and die yields the VGA thermal camera is more common these days. It remains a much more expensive camera for the reasons already mentioned but is to be found in thermal CCTV cameras that offer wider fields of view whilst offering similar image detail to that of narrower field of view QVGA models. Bargains can be found on the secondary market but VGA cameras and cores are not something I feel is necessary for most PCB thermal analysis tasks. There will be exceptions however, such as in Science Labs etc, but they are in the minority in the context of this thread.


There are sensor array resolutions higher than 640x480 pixels but I have decided to ignore those here as they are too specialist and expensive for the intended readership of this thread.

SEEK Thermal produce an unusual 200x150 pixel resolution sensor array that is to be found in many of their products and the products of those OEM’s who buy SEEK Thermal cores. That resolution falls between the 160x120 pixel and 256x192 pixel sensor arrays. Given a choice, I would choose the 256x192 pixel sensor array over the SEEK Thermal product.

As a footnote to this post……..

Be wary of products that appear to offer surprising resolution at unusually low cost. For many years there have been manufacturers who will use a low resolution thermal sensor array and apply interpolation to its output so that higher resolution may be claimed in the specifications ! The use of interpolation without it being clearly stated is deception. Some manufacturers also provide the LCD display resolution in the specifications rather than the true thermal sensor resolution in the hope of tricking the buyer. Note that it is normal for a manufacturer to upscale a thermal image to fit a nice high resolution LCD display…. For example a 320x240 pixel thermal image may be upscaled to a 640x480 LCD panel. That is very different to using a 96x96 pixel sensor array and stating a thermal resolution of 240x240 in advertisements ! HikMicro have the ECO range of cameras that do this BUT they make it clear in adverts and specifications that the true sensor array resolution is 96x96 pixels.
Be careful…... If it looks too good to be true, it often is where new thermal imaging equipment is concerned.

It is also worth being a little curious about any thermal camera that has a 1:1 aspect ratio sensor array. Most modern microbolometer arrays have the common 4:3 aspect ratio. Anything different to that may suggest the use of a less common sensor array type or technology. HikMicro are supplying 96x96 pixel arrays for their economy product lines. Their choice of 1:1 aspect ratio is interesting and they must have their reasons for such. The number of dies per wafer could be a factor in their decision.

[Fraser]

Lens System, including field of view, minimum focus distance and quality

It is important to not become fixated on a cameras resolution and ignore other important specifications that effect performance when viewing a PCB. An important part of a thermal cameras design is the optical block. The optical block is the group of lenses that sit in front of the sensor array and illuminate it with the thermal scene. The quality of lens elements, lens block design and field of view will all influence the image produced by the thermal camera. Let us look at the lens block in terms of what is desirable for PCB thermal analysis work.

a) Field of view

Field of view (FOV) is a very important specification when comparing thermal imaging cameras, especially cameras with different resolution sensor arrays. The FOV of the lens block has a direct influence on the detail visible on a PCB at a specified distance and this should be well understood by those considering a purchase. I am going to avoid maths here and go with simple cases that illustrate my point well.

Let us take a “Standard camera” with 320 x 240 pixel microbolometer being illuminated by a lens block that provides a horizontal field of view (HFOV) of 50 degrees. This means that the 320 pixels are each taking a share of the 50 degree HFOV. This will mean that each pixel sees 0.156 degrees of the horizontal scene (50/320=0.156). A 50 degree HFOV lens is quite wide angle and Industrial QVGA thermal cameras often use a 24 Degree HFOV lens. In that case each pixel sees 0.070 Degrees of the horizontal scene (24/320). So we can see that by halving the HFOV we gain double the amount of available detail in the scene whilst losing half of the horizontal scene coverage. Losing coverage area of a scene is sometimes acceptable as multiple images may be captured for full coverage. The level of “granularity’” in the scene data can be more important than scene coverage. Bare this in mind with what follows

If we take our “Standard camera” with its 320 x 240 Pixel sensor array and 50 degree HFOV lens block and compare other cameras of lower resolutions with it, what do we find ?

Case 1.

A camera with a 160x120 pixel sensor array and 50 degree HFOV lens is compared to the “Standard camera” at the same viewing distance from a PCB. We see a thermal scene on both cameras that covers the same area of the PCB. We note that the 160x120 pixel camera is showing less detail (granularity) in the image and this is because it has half the number of pixels in each vertical column and horizontal row of the sensor array. This is a quarter of the number of imaging pixels covering the same area of the PCB. The difference is definitely noticeable but the components on the PCB will still likely be imaged if producing heat.

Case 2.

A camera with a 160x120 pixel sensor array and 25 Degree HFOV lens block is compared to the “Standard camera” at the same viewing distance from a PCB. We see a thermal scene on both cameras but the area of the PCB displayed on the 160x120 pixel camera is a quarter of that being displayed on the 320x240 pixel “Standard camera”. The level of detail (granularity) within both cameras scenes is, however, the same. In this case the scene detail has bee prioritised over scene area on the 160x120 pixel camera. We see one quarter of the PCB area but obtain the same scene detail as a camera with four times the number of pixels. This trade-off means that a cheaper camera can still resolve the same level of detail in a scene as a more expensive camera that has higher resolution.

In the above simple examples we can see that lens choice is important. Whilst a manufacturer may opt for a 50 degree HFOV lens with a certain resolution of sensor array, a particular application may benefit greatly if the same resolution of sensor is chosen, but with a narrower field of view lens, to provide more scene detail. The FLIR E8 has an HFOV of around 45 degrees for general observation work using its 320x240 pixel microbolometer. My FLIR E60 has an HFOV of around 25 degrees with the same number of pixels observing the scene. Whilst the E60 covers less of the thermal scene area at a given distance, it provides greater detail (granularity) in the displayed thermal scene. Supplemental lenses are available for the E60 that can half or double the field of view but, just as in the examples above, there is an effect on the scene coverage and scene detail.
I hope this makes sense !

b) Minimum focus distance

A lens block will provide a certain field of view, as already discussed. It will also have a specification for minimum focus distance. This is the minimum distance between the cameras lens and a given target at which good focus may still be achieved. The situation is somewhat complicated by the fact that some thermal cameras use a “Fixed Focus” lens, whilst others use a “Manual Focus” lens. There are also true “Auto Focus” lenses available. With “Fixed Focus” lens blocks the lens is actually focussed at the hyperfocal distance that provides acceptable focus between a stated minimum distance and infinity. Such fixed focus lens systems can be very convenient for a user as no focus adjustment is required. That said, these fixed focus systems are a compromise and do not provide the best possible focus at all points of their range coverage. Some fixed focus lens systems may be manually adjusted to favour focus at closer distances than the manufacturer intended. A manual focus lens system requires the user to manually adjust the lens block for optimum focus of the target. Whilst this may be less convenient for the user, it can mean sharper images are produced as the focus is optimised for a particular targets distance from the camera. Manual focus lens systems will also have a specified minimum focus distance but users may find that closer focus than specified is possible. With simple screw in lenses the lens is wound out of the lens holder on a fine thread and the length of that thread often dictates the closest focus before the lens barrel falls out of the lens holder, or hits an end stop to prevent such ! Auto focus lens blocks come in various designs that will not be detailed here. They have a specified minimum focus but their distance detection systems may complicate matters for PCB use. The focus servo system may take its focus point data from a distance detecting sensor, such as ultrasonic or infrared but modern systems tend to use image detail based focus detection. Such systems can struggle in low contrast thermal scenes. For PCB repair work, it would be best to avoid auto focus lens focussing systems unless they may be set to a manual focus mode. The minimum focus distance is an important specification when selecting a thermal camera for PCB repair work but there are ways to adapt a camera to focus closer than the minimum focus distance. These will be discussed later.

The distance between the target and the camera is an important consideration. Just as was detailed in the discussion of lens FOV, the distance from the target effects the amount of available thermal detail (granularity) captured by the camera. In a given situation, if you half the distance between the camera and target, you quadruple the image detail provided in the captured scene but observe one quarter of the original area. This only helps if the camera can actually focus on the target at half the original distance however ! Doubling the distance between the camera and the target has the opposite effect….. a quarter of the detail in the captured image but four times the area covered in one scene capture. For the reasons detailed, it can be an advantage to get as close as practical to a PCB containing modern miniature SMD components if the greatest detail is desired from a relatively low resolution sensor array. The desired distance may well be closer than the cameras specified minimum focus distance, and be warned that a poorly focussed thermal image is a most undesirable situation ! We can add a close focus capability to a camera with nothing more complicated than a single lens element placed in front of the cameras standard lens. For this reason, do not discount a particular camera model because it has, for example, a 30cm minimum focus distance.

So how do we produce a close focus accessory for a standard thermal imaging camera. Well there is plenty of information about this on the EEVBlog thermal forum but in précis, you buy a ZnSe Planar Convex or Meniscus lens that is designed for use on a CO2 laser engraver and mount it in front of the cameras normal lens. You are effectively giving the camera a reading monocle ! Such “close-up” lenses are also used in visible light photography for Macro photography. The ZnSe lens elements are inexpensive and available in several diameters and focus distances. With regard to diameter, it is important to select a lens element that is large enough diameter to avoid vignetting. Focus distance is a mater of preference. I personally use 100mm, 63mm and 50mm focus distance lenses for PCB work. The lenses focus distance specification will approximate to the focus distance that is achieved for the camera when the lens is in use. The depth of field is shallow so the correct working distance is important. With such a lens fitted, a thermal camera normally incapable of focussing closer the 1m can focus on a PCB at just 50mm distance ! This technique works for both fixed focus and manual focus lenses but I find that manual focus lenses still provide the best image clarity. Thermal camera manufacturers have caught on to the market demand for close-focus lenses and several produce official close-focus lens accessories for their cameras. DIY close focus lens mounts are also common and various 3D printable designs may be found on Thingiverse etc. The lenses are common on eBay and often come from China at low cost.

Another possible option for closer focus capability is the manual adjustment of the fixed focus lens to permit close focussing, but this will be at the cost of normal distance focus unless the lens is returned to its hyperfocal distance after use on a PCB.

c) Lens block quality

It should now be clear to the reader that the lens is an important part of a thermal cameras design and errors in that part of a cameras design will impact imaging performance. We need to consider how much of an issue this truly is with modern budget thermal imaging cameras and their use for PCB observations.

In the early days of thermal imaging systems, the lenses were highly specialised products as they used an unusual lens element material that was hard to work with and special anti reflective coatings on the lens surfaces. The cost of these lenses was truly eye watering ! The material used to make the thermal imaging lens elements was/is Germanium that is grown as a single crystal before being cut to the required shape on a diamond lathe. The Germanium lenses made thermal imaging cameras inherently expensive beasts so research into cheaper alternatives began. Other materials, such as GaAs, ZnS and ZnSe may be used for thermal imaging lenses but each has its drawbacks. A new lens material and production method was developed and we now have the Chalcogenide IR moulded glass lenses that are found in modern thermal imaging cameras in the budget/semi-pro market sectors. The new lenses are made from a mixture of Germanium and other materials that may be hot moulded rather than cut on a diamond lathe. Both the raw material and the production process significantly reduced mass production costs for the industry.

Now whilst Chalcogenide IR glass moulded lenses (aka GASIR lenses) revolutionised affordable thermal camera mass production, it should be understood that this new “wonder material” is a compromise compared to a pure mono crystal Germanium lens. This is why Pure Germanium lens elements are still used in high performance professional thermal cameras. That said, Germanium lens systems suffer from issues if they get too hot as transmission reduces with increasing physical temperature. For PCB analysis use, I see no problems using the affordable Chalcogenide IR Glass moulded lenses common in budget thermal cameras as they still perform very well.

There have been lenses produced in the budget thermal imaging sector that did not impress me though. The FLIR Lepton uses a different approach to its lens construction. The Lepton wide angle lenses are created in silicon using the MEMS process, so are effectively printed lenses of the Diffraction type. I will be honest and say that I dislike those lenses. They were another approach to affordable thermal imaging lens production but they are, IMHO, inferior to Chalcogenide IR Glass lenses.

We have discussed lenses here but need to be aware that a lens block is only as good as it’s optical design and some manufacturers may make mistakes when designing a lens group for their lens block. Mistakes happen ! Do not assume that all Chalcogenide IR glass lens blocks will perform the same. It is best to see real world imagery from a particular camera of interest to assure yourself that the produced images are as crisp and well formed as you would expect. A poor lens design can cause poor image geometry and poor focus, amongst other issues. There is also the issue of the care taken at the factory to set the focus on a fixed focus lens camera. There can be improvement in image clarity on some cameras if the lens is focussed carefully by the user. Such corrective action should not be necessary in a properly set up product, but these are mass produced cameras and cores !

[Fraser]

Minimum resolvable temperature difference (MRTD)

Much is often made of a thermal cameras sensors Noise Equivalent Temperature Difference (NETD) and this is a specification often used by manufacturers to “out-specification” their market competitors. In my experience NETD has been a much abused specification and it is actually quite hard for most end users to test in order to confirm the claimed performance ! Whilst it is true that newer generations of microbolometer sensor arrays improved the NETD figures through design and manufacturing improvements, I would suggest that users not get too “hung-up” on NETD figures. Professional thermal imaging cameras used to have NETD figures of 100mK yet those cameras were more than capable of use in most thermography applications in which a microbolometer based camera was acceptable. Exceptions are the specialist applications that need extremely low noise imagery and these tend to use cooled thermal imaging cameras. It is true to say that a camera sensor array with a genuinely lower NETD can better show very small temperature changes than one with a higher NETD figure but in most PCB analysis cases this is not a big deal.

For more information on what NETD actually is, see this page:

https://movitherm.com/blog/what-is-netd-in-a-thermal-camera/

I have deliberately titled this post “Minimum Resolvable Temperature Difference” as this is a specification that you will rarely find in the world of budget thermal imaging cameras ! It is what it says….. The minimum temperature difference in a scene that the user can see using the supplied camera SYSTEM. Note that his is a specification relating to the whole camera system and NOT just the specification of the sensor array tested under laboratory conditions for best possible NETD figure ! In other words, MRTD is more of a real world test specification than the “Laboratory test” world of NETD. Some camera manufacturers just take the best possible NETD figure from the sensor array manufacturers data sheets and paste that into their cameras specifications sheet. It is likely no testing of “System NETD” ever takes place on budget cameras. There are many things in a complete thermal camera system that can adversely effect the MRTD and it is good to know this when focussing on claimed NETD figures ! MRTD is the testing of a complete camera system , as supplied to the customer, to determine exactly what temperature difference is visible to a user with the provided lens block and display panel. This is a far more useful test of a thermal camera and I only mention it to highlight how relatively misleading NETD can be in a specification as it related only to the sensor array (in isolation) that is being illuminated by a quality F1 lens.

So is low noise and the ability to detect very small temperature differences important when working on a PCB for the purposes of repair ? Well yes and no. Much depends upon the specific scenario. When it comes to spotting things like overheating components of components that are just emitting a decent amount of thermal energy, high sensitivity to temperature differential is not so important. If, however, the user is trying to use low stimulation currents to detect a shorted component or PCB trace, the sensitivity of the camera to very small changes in temperature can become more important. In many cases, if a short cannot be identified at very low currents, the stimulation current is just increased carefully until the thermal camera can see the component or track becoming detectably warm. A classic case is failed MOSFETs on computer PCB’s that only display the slightest change in temperature due to their very low resistance to ground when failed. A sensitive, low noise, thermal imaging camera will detect the small “hot spot” on the MOSFET at a lower stimulation current than that needed for a lower sensitivity, more noisy, thermal camera. In real world scenarios I believe that any thermal camera with an NETD figure better then 80mK will be more than adequate for PCB repair work. It must also be remembered that tracing shorted tracks on a PCB is challenging if the track is within the many layers of the PCB. Higher stimulation currents may be needed to warm the copper pours above and below the track to show its presence within the PCB. Use of sensible stimulation currents will not cause damage to a PCB as the thermal camera will see the thermal energy well before enough heat is generated in the track to damage it or the PCB. Basically do not worry too much about the difference between a claimed NETD of 45mK on one camera and a claimed NETD of 60mK on another camera.

[Fraser]

Temperature measurement range and and accuracy

Users need to consider the temperatures that they are likely to come across in their usage scenario as some thermal cameras may be incapable of measuring such temperatures. A classic comparison would be measuring the temperature of a micro-processor vs measuring the temperature of a vitreous enamel power resistor. The Micro-processor is likely to be running at a temperature below 100 Celsius, but a vitreous enamel power resistor is capable of operating normally at over 400 Celsius in free air. Whilst a thermal camera capable of measuring up to 150 Celsius will cover most likely temperatures on a computer PCB, it would be of little use if wishing to measure the operating temperature of a Vitreous enamel power resistor that is operating at around 250 Celsius. That said, sometimes it is enough to see that something is “HOT” in a system without actually knowing the current temperature…. Evidence of life in a system is such a use case. Be aware that if a thermal camera manufacturer states the maximum measurement temperature is 120 Celsius, it is highly likely that viewing targets in excess of that temperature, whilst not damaging to the camera, will not be displayed correctly and measurements may be flawed or not possible. Some thermal cameras start to display image artefacts when viewing a target that is at a higher temperature than the stated maximum measurement temperature of the camera. This is often due to reaching the end limit of the systems ADC that converts the microbolometer ROIC analogue output to digital data. Thermal cameras that are capable of broad temperature measurement ranges normally use multiple ranges that are manually or automatically selected to suit the expected target temperature.
Selecting the best thermal camera for a usage scenario is basically common sense. How likely will it be that high temperatures will need to be measured. If it is not likely then a single range (cheaper?) camera with a maximum measurement capability of 120 Celsius may be enough for you. If high temperature targets are expected and their measurement important, a higher specification camera with a high temperature range is required but expect the cost to be higher for a given resolution.

So we have decided upon a suitable measurement temperature range that will be required of the thermal camera, but what about measurement accuracy ? Measurement accuracy is a bit of a minefield in the realm of thermal imaging. Even if a particular camera is as accurate at measuring temperature as is claimed in the specifications, there are other factors that will effect the accuracy of any measurements so we need to be sensible when looking at claimed measurement accuracy. Most thermal imaging cameras have a stated measurement accuracy of +/-2% or +/-2 Celsius. This is a very common specification and most thermal cameras that I have tested meet this specification (some only just though !). It is common for me to find thermal cameras from well respected manufacturers performing considerably better than their specification for measurement accuracy. Since the Covid-19 Pandemic a new measurement accuracy specification has become common amongst thermal cameras intended for human fever screening. The Worlds Governments decided that an accuracy of +/-0.5 Celsius was required when measuring people in the search for Covid-19 infections. A tighter +/-0.3 Celsius specification was also created for thermal cameras that use a Blackbody thermal reference to improve measurement accuracy. If a fever detection thermal camera system could not meet these specifications, it was rejected for use against Covid-19. For this reason these new, tighter, measurement tolerances can be seen on some specialist use cameras associated with measuring human targets. Note that the measurement accuracy is only applicable over a stated target temperature range, often +30 Celsius to +45 Celsius. For PCB use, the greater accuracy of these cameras is likely not useful due to their limited measurement range. That said, some surplus fever detection thermal cameras make very useful PCB diagnostic tools provided it is understood that some cannot measure outside +25 Celsius to +50 Celsius. Or even more restricted temperature ranges in some cases. Despite the measurement limitation, these camera still behave normally with regard to displaying a thermal image of the scene, with most having an upper display temperature limit of +100 Celsius or more.

So what can effect the measurement accuracy of a thermal imaging camera beyond the base accuracy of the camera itself ?

Common factors that effect measurement accuracy are…..

a) The selection of the most appropriate Emissivity on the camera for a given target. This is often not known by the user so a best guess is entered using Emissivity guides. A guess that is not correct introduces a measurement error.

b) Distance to target entry on the camera. The distance between the camera and a target is taken into account when a thermal camera makes a measurement. In the case of PCB imaging the camera is very close to the target so path compensation is less critical but a sensible entry is still needed in the distance to target menu.

c) Reflected temperature setting on the camera. The correct “Reflected Temperature” entry on the camera can be important when working with a target that may be being illuminated by an nearby thermal energy source, such as a heatsink. Ignoring Reflected Temperature can lead to measurement errors.

d) Additional lenses or materials in the optical path will degrade the cameras measurement accuracy unless these are compensated for. Examples would be the use of a lens protection film, such as Polyolefin film, or the use of a ZnSe close-up lens in front of the normal camera lens. Anything in the optical path that does not have perfect transmission at LWIR (microbolometer cameras) will have an effect on the cameras measurement accuracy.

A thermal camera user who is making measurements on a target needs to consider whether the camera is the best and most appropriate tool for the task. The cameras measurement accuracy is adequate for many tasks and very convenient, but a more accurate “contact” type temperature measurement sensor may be needed where greater accuracy is required.

[Fraser]

Frame rate(image update rate)

Frame rate limits on thermal cameras involves Regulations, International Agreements, processing power and technology limitations.

Most microbolometer modules are capable of decent frame rates of 30fps, 60fps and even 120fps. Long standing International agreements have limited the frame rate of thermal cameras to less than 9fps if they are to be sold without the more involved end user checks and licences. In recent years the China sourced thermal imaging cores and thermal cameras have commonly offered 25fps to anyone wanting to buy such a camera or core. Even SEEK Thermal, a US company, has sold thermal cores and cameras capable of 15fps without end user checks. With the advent of Chinese 256 x192 pixel 25fps thermal imaging cores and cameras, the frame rate limitation regulations appear to be becoming more and more outdated. Whilst it is true that the USA has sanctioned IRAY for selling thermal imaging technology to Russia, the international supply of 25fps thermal cameras continues unchecked. With this in mind, if you do not have issues with buying a Chinese product, there is the incentive of a decent frame rate to consider. Whilst a <9fps thermal camera works perfectly well for PCB inspection and repair, the increased frame rate adds to the cameras versatility and it can better capture images of moving objects. I know of at least one manufacturer (Infiray) who offered a 256x192 pixel camera dongle with 50fps update rate but that camera dongle had issues with measurement accuracy and I am uncertain whether measurements could be carried out at the 50fps frame rate (it allowed a 25fps frame rate as well). Do not get blinded by impressive frame rate claims. Do your research and make sure that a higher frame rate does no incur negative effects on other areas of the cameras performance. Also remember that a dongle type thermal camera relies upon the processing power of the host phone/tablet and frame rates can drop if the phone is multitasking or does not have a processor with adequate number crunching power. Such limitations may only become evident when trying to record thermal videos. It is not unknown for there to be compatibility issues between some thermal phone dongles and certain brands of mobile phone. These incompatibilities can cause failure to connect or choppy frame rates.

[Fraser]

Camera format for PCB work

The case format of a thermal imaging camera is very much a matter of personal preference. There are, however, some practical considerations when considering a camera for PCB inspection and repair. The camera may be hand held or mounted on a stand depending upon the users preference. Whilst hand held is great for manoeuvring around a PCB or equipment with speed and ease, it does tie up the users hand and maintaining proper focus can be a challenge. An alternative is to rigidly mount the thermal camera on a base or articulated arm. The PCB is then moved around under the cameras view without needing to be held or focus adjusted. There are pros and cons to both approaches and I have used both. I have to admit that hand holding is my most used technique.

Thermal cameras come in many form factors so we will discuss a few here, but it is for the user to decide which form factor best meets their personal needs.

a) The Camcorder/Palmcorder format.

This is an older format for thermal imaging cameras that is mostly ignored by modern thermal camera manufacturers. The camera is held like a normal video camcorder or Palmcorder when hand held and may be rigidly mounted on a stand or tripod when a static mount is desired. The older cameras, such as the FLIR PM695 are great performers but relatively heavy due to the all metal construction. This style of camera is a favourite of mine for mobile working but not used by me for PCB inspection.

b) Pistol grip format.

The pistol grip format of thermal cameras has become a favourite of many end users and manufacturers. It offers a good grip of the camera by the user whilst offering a nice clean view of the display. Controls may be positioned around the cameras case fro operation by the users fingers and thumb. A firm favourite format for many users of technology. These cameras often provide a tripod mount built into the cameras case or as an accessory part. The ability to use the camera in a handheld or static mount scenario makes it very versatile. The display is usually fixed so the user can find it difficult to view when looking straight down on a PCB. The camera is often used at an angle of 45 degrees to the PCB for this reason. This is a versatile case format that is useable for PCB inspection without too many ergonomic issues.

c) Thermal scope format.

The thermal scope format is really intended for observation applications and not well suited to PCB inspection. The use of a small EVF forces the user to press the thermal scope to their face so this makes for an interesting user experience if a close-up lens is in use on the scope. The user will find their face and nose very close to the PCB ! Not a format that I can recommend for PCB work !

d) Phone dongle Thermal camera format.

Another very popular thermal camera format is the phone dongle. These cameras use the phone to process and display the thermal data for the user. They are normally directly mounted on the phone via host the USB/Lightning connector. Whilst such a mounting method is not a favourite of mine, the dongles are normally both small and light in weight, so seem to stay put on the phone. The dongle camera offers the user the option to attach the camera to ten phone via an umbilical cable. This is just a standard extension cable but it permits the camera to be positioned remotely from the host mobile phone. When connected via an umbilical cable, the camera may be positioned at any angle desires whilst the phones screen is positioned for easiest viewing. This can be very useful for PCB and equipment inspection work. The camera dongle may be attached to a articulated arm or bench stand, looking down on a PCB, whilst the phone is angled on the bench for easiest use. The camera may also be used in confined spaces a little like a bore scope which adds to its versatility. The down side of such a camera format is its reliance on another piece of equipment to form a complete system. A user may, or may not have a suitable mobile phone and such can be expensive if a new one is needed. I purchased used mobile phones with damaged SIM sockets, failed earpiece audio or no phone network connectivity for use with my dongle cameras. These faulty phones were inexpensive.

e) Static camera format also seen in CCTV use cases.

Static thermal cameras are intended to be mounted on a rigid mount from which the camera on serves a scene. There is nothing to stop a static camera being used for PCB work as they may be mounted on a bracket or arm, looking down on the PCB from above. The image information is usually fed to a laptop or tablet PC for display and camera control. An Industrial static camera will often be very capable as such are used in both industry and science environments. Thermal CCTV cameras, whilst still an option, are less versatile and the control software dedicated to their intended CCTV observation duties. A close-up lens is needed to use a thermal CCTV camera for PCB use as the minimum focus distance can often be 1m.

f) Mini tablets and mobile phones with integrated thermal cameras

The mobile phone and tablet format is common in modern society so it is no surprise to see thermal imaging solutions in this format. Thermal imaging cores were integrated into rugged mobile phones to meet the needs of those who are mobile and always want a thermal imaging capability with them. The mini tablet camera format then arrived on the market for users who like the format but do not need the phone and computer functionality. Both mobile phone and tablet formats are easy to hold and use but choice has been limited in the marketplace. Many such solutions used the FLIR Lepton core but we are now seeing the Chinese imaging cores being used in newer models. Such a case format is useable for PCB repair work. I do not find the format as easy to hold as a pistol grip format but this is also true of the phone dongle format. The phone and tablet format may be mounted on an articulated arm using clamps intended for holding mobile phones.

g) Dedicated PCB inspection and analysis systems.

Once the usefulness of thermal imaging for PCB inspection was realised, manufacturers started to create dedicated PCB inspection systems. Most are basically a thermal imaging head, similar to a mobile phone dongle thermal camera, that is mounted on a bespoke bench stand that can be simple or quite complex in design. The camera connects to a host computer that may be a mobile phone, tablet computer, laptop or desktop PC. The systems include bespoke PCB analysis software to make them a very capable thermal analysis tool for both repair and R&D activities. For the user wishing to have a fixed PCB analysis solution for the test bench, they could do worse than buy one of these dedicated systems. As a dedicated solution they are somewhat limited in terms of other use cases but the camera head is just a standard, often manual focus dongle thermal camera so may be sure much like a standard dongle format camera on an umbilical cable if desired. FLIR produce a more refined solution in the form of the ETS320. This offers a 320x240 pixel thermal camera (Fixed focus distance) and display in a dedicated case format that is mounted on a desk stand. In my experience, the ETS320 is no better than the cheaper 256x192 pixel dedicated PCB thermal analysis solutions that have come out of Chinese companies like Dianyang Technology and Quianli. Some customers would prefer to buy a USA based FLIR product however.

It should be noted that some dedicated PCB analysis solutions are intended to be used with mobile phones and similar. This can mean that the working area under the camera is restricted so large PCB’s will not easily fit in the available space.

h) Multimeters with integrated thermal camera

FLIR was one of the first (the first ?) companies to incorporate a thermal imaging capability in a Multimeter. The market has seen all manner of enhancements added to the humble Multimeter over the years but this was the first time that I had see a thermal camera inside one. The thinking behind the design is sound as the Multimeter is intended to be a very versatile tool and the inclusion of a thermal imaging function would certainly be useful to electricians etc. such a feature is only useful if it works well however. FLIR uses the Lepton core in their unit so imaging is acceptable. Recent thermal camera equipped Multimeters coming out of Asia are more affordable than the FLIR offerings, but thermal image quality varies greatly between models so potential buyers need to do their homework before buying. The case format is designed to be hand held but can be quite bulky. Very useful for the odd quick thermal image of a scene but not optimal for general thermal imaging of a PCB in my opinion. If it is the only Multimeter the user has then the meter leads will be dangling from it and it may even be in use on the test bench when wishing to do some thermal imaging of the PCB. I would love such a unit on my bench, but purely for novelty value.

[Fraser]

Image capture, Image Analysis Software and mobile phone Apps.

Many users of a thermal camera for PCB analysis will operate i. Real time observing the thermal profile of ten PCB and its components in the search for anomalies. Such a need is well catered for by all of the thermal imaging solutions as the user is presented with the thermal scene in real time on the provided display. Some users may wish to capture still of moving images for the purposes of reporting or teaching others about a particular fault. Most thermal imaging camera solutions support the capture of still images but not all support the capture of video. Amongst those that support video capture, only some offer thermal analysis of the video after capture. It is worth checking a cameras specifications to determine whether it supports the required recording modes. Do check the frame rate capability with video recordings as a high frame rate thermal camera may be capable of relatively low frame rate video recording. Still images can come in various forms. Some use proprietary data formats that limit image analysis to only that which can be achieved with the manufacturers software. Still image files can contain just spot temperature metadata or metadata from every pixel within the image. This maters if the user wishes to carry out comprehensive image analysis based upon a captured thermal scene. It is always better to have the thermal data for every pixel in a saved image as this permits the image analysis program to access all that data, rather than just display the temperature data of a single, or multiple measured points in the scene. Some thermal imaging cameras offer very little by way of post capture image analysis and this could be an issue for some users.

Dongle type thermal imaging cameras use a mobile phone as the host computer to process the thermal image data and display it on the phones screen. The issue that must be remembered with mobile phones is their relatively short life expectancy. All too soon a mobile phone can become obsolete (churn on mobile phones is commonly 2 years) and this can lead to issue with OS and APP updates. Many users of mobile phone dongles have concerns that their perfectly good thermal camera dongle may effectively be rendered useless for no other reason than the phone technology has moved on and rendered their ‘old’ dongle obsolete through lack of new APP releases by the manufacturer. I use dedicated mobile phones for my dongle cameras, as previously detailed, and expect to have phones to support my dongle cameras for years to come. I do not need to change the OS on these phones so as long as the APPs continue to work, as they do today, I am OK. At some point ten thermal camera dongle manufacturer may cease updates or backward compatibility for older dongle cameras but that should not render these cameras useless if you plan ahead.

If wishing to carry out any sort of detailed thermal profiling or analysis of a PCB, rather than just live observation, I suggest that care is taken when purchasing a thermal camera to ensure that the manufacturer offers an image analysis software package that does what you need. Do make sure that adequate radiometric data is present in saved image files as that data is essential to post capture image analysis.

[daisizhou]

As far as I know, the current cheap solution is MLX90640, but this solution is not perfect and there are delays and freezes.

For TS-4117 solution, please see https://oshwhub.com/lxu0423/lithermal-thermal-imaging-camera

If there is a better solution suitable for amateurs and cost-effective, please recommend it, thanks

[Fraser]

Daisizhou,

I can only recommend a camera after testing and I have no access to the TS-4117. If someone gives me a camera to test, I am happy to review it for this forum. This particular thread is more about discussing camera specifications suited to PCB repair rather than individual camera models. That said, I have no issue with people detailing their personal experiences with a particular model of camera though 

Fraser

[artag]

Anything else I can think of !

To be continued………

Documentation.
Whilst an included app or hardware may be sufficient to make straightforward use of the camera and OEMs may have access to full documentation, it is becoming increasingly possible to make vertical market devices that either incorporate themal camera features or offer open source access to devices that have been proprietary.

If you're designing a system, you probably don't want a device that's fully integrated or supported only by an Android app. For this reason, I'd ask that the vendor's support for application development or the presence of reverse-engineered interfaces be mentioned as an attribute of cameras.

[ArsenioDev]

As far as I know, the current cheap solution is MLX90640, but this solution is not perfect and there are delays and freezes.

For TS-4117 solution, please see https://oshwhub.com/lxu0423/lithermal-thermal-imaging-camera

If there is a better solution suitable for amateurs and cost-effective, please recommend it, thanks

Do you have a reliable source for the HikVision modules?

[Fraser]

Well I have completed what I wanted to write at the start of this thread.

That is enough from me for now ! I still need to review what I have written today to correct typos and my iPad’s auto-correct cock-ups ! That can wait until tomorrow though.

Fraser

[Fraser]

It would be really good if forum members who already own thermal cameras would upload images of PCB’s captured with their camera
This will give readers an idea of the different camera capabilities and what to expect if buying a particular camera model. Even a single image of an R-Pi with details of the camera model would be helpful to readers. Try to capture an image as close to the PCB as possible whilst maintaining good focus to show what can be achieved with that model of camera.

This thread could become a good reference for those who want to buy a thermal camera for PCB repair work 

Fraser

[Leon W]

The current 4117 module solution in China is very mature, and the volume of modules in the market is also very large. When paired with corresponding lenses, it can achieve very good effects. Many teams have already developed many playful applications with this module, and the price of the 4117 module itself is also very affordable, around 400 RMB.

[daisizhou]

The current 4117 module solution in China is very mature, and the volume of modules in the market is also very large. When paired with corresponding lenses, it can achieve very good effects. Many teams have already developed many playful applications with this module, and the price of the 4117 module itself is also very affordable, around 400 RMB.

100 RMB is a reasonable price, while 400 RMB has a significant premium.
Usually 100RMB is second-hand, and most of these modules are second-hand. Buying brand new is meaningless

[ArsenioDev]

Where can we Actually purchase these at 1-400rmb pricing? and are there datasheets?

[Fraser]

ArsenioDev,

The TB-4117 is a Pandemic human temperature measurement core from Hikvision that is now surplus so the supply chain is unpredictable. I have seen them offered on Aliexpress, but at £70 each, so not of great interest to me. It is a 25fps 160x120 pixel core with 37.5 x 50 degree FOV.
This page has some documentation……

https://www.visiotechsecurity.com/en/products/ip-cctv-1/body-temperature-fever-416/thermographic-cameras-417/tb-4117-3_s-detail#tab=prod_3

Bulk seller on Aliexpress…….

https://www.aliexpress.com/item/1005006718594182.html

Fraser

[mzzj]

It would be really good if forum members who already own thermal cameras would upload images of PCB’s captured with their camera
This will give readers an idea of the different camera capabilities and what to expect if buying a particular camera model. Even a single image of an R-Pi with details of the camera model would be helpful to readers. Try to capture an image as close to the PCB as possible whilst maintaining good focus to show what can be achieved with that model of camera.

This thread could become a good reference for those who want to buy a thermal camera for PCB repair work 

Fraser

You got bit carried away with the warm-up story 

UNI-T UTI260A:
heated car steering wheel without extra lens:



UTI-260A + ZnSe lens (Cloudray 20mm F50,8mm "USA CVD")
Arduino Nano PCB with some wires crisscrossing over the pcb


Camera and lens were total 260 EUR delivered to home door. Only bigger complain I have is that UTI-260A doesn't have manual ranging for the temperature scale. Any hot object in the field of view autoscales the range and you can't look for any small details.
For example if you are looking for pcb trace temperatures the "hot" trace could be 5 degrees hotter than others and if there is a ceramic power resistor running at 200Cel it will make it nearly impossible to find small differences as the autoscaling ranges to 20...200Cel range   

[Fraser]

Mzzj,

There is no “warm-up story”. This thread is intended to help readers understand the specifications and types of thermal camera that may be used for PCB repair. Readers can scroll past bits that are not of interest. The addition of images is to help readers to actually see the differing performance of cameras that they can buy.

Manual setting of centre temperature and span is a very useful feature that is sadly often lacking on budget thermal cameras as manufacturers seem to want the camera to configure itself for best imagery so that they are easy to use. Providing a full manual mode costs nothing but risks inexperienced users configuring the camera poorly and believing that it has an issue. In your example there are two options…. Get closer to the area of interest with a close-up lens to exclude the hotter area from the scene, or use simple masking with a piece of cardboard to exclude the hotter area from the cameras view and auto ranging. A narrow field of view camera can be advantageous in these circumstances.

[Fraser]

Sadly it appears that there is not much interest in adding real World pictures to this thread. People have very busy lives these days so I totally understand. Sadly I have no more spare time to populate this thread with pictures from cameras in my collection (it takes time to set up and capture useful images). I hope that the written content of this thread will be of some use to those venturing into the World of PCB thermal imaging. The thermal camera can be a very useful tool for understanding what is happening on a faulty PCB or power supply…. a real time saver in many cases. It is not the panacea for all PCB faults though….only those where a heat signature can tell you something useful about the fault.

Regarding the cheapest thermal cameras available on eBay that use the Melexis MLX90640 imaging sensor array, I recommend saving your money and buying a thermal camera that has at least 120 x 90 pixels, or better still, 256x192 pixels. You will soon grow out of a very low resolution camera and so have to buy twice rather than buying well first time around. My personal recommendation for a decent thermal imaging specification for PCB repair work is :

Resolution : 256x192 true physical pixels

Lens FOV : 50 Degrees or narrower

Frame Rate: 25fps (<9fps if no other choice)

NETD: Anything better than 80mK is fine in this application

Format: Personal preference - you decide !

Software: if just carrying out live imagery checks on a PCB, this is less important. If wishing to analyse imagery, you will need a software that can select different palettes, carry out multiple spot temperature measurements and hopefully offer decent thermal analysis tools such as ROI, Max/Min highlighting, manual span and centre temperature, measurement lines and geometric shapes for ROI. There may be image enhancement available as well. Basically thermal image analysis software should allow you to manipulate most aspects of the image and provide measurement tools to gain further knowledge of the thermal scene. Some software is more about image editing and basic measurements. A camera that streams or saves fully radiometric imagery is needed for detailed thermal analysis work (every pixels data provided in stream or file)
Manual control : The inclusion of a manual span and centre temperature control is very useful, but not essential if budget limits availability.

Brand: This is subjective, though I personally found that Infiray, Guide Sensmart and Hikmicro cameras are well designed and built. I am a little less keen on Uni-Trend but the UTI-260B remains a very strong contender for a thermal camera that is well suited to PCB repair work. If cost is not a problem, then buying a decent specification FLIR thermal camera (not the budget consumer models) will normally satisfy all of your needs for many years to come. Other professional brands are available and offersimilarly impressive performance. It may be noted that I am recommending cameras that are made in China. It is a fact that Infiray, Guide Sensmart and Hikvision/HikMicro are currently dominating the marketplace with decent resolution, affordable thermal imaging cameras so they get my vote.

Close-Up lens : Many thermal cameras, including the professional models, benefit from the addition of a close-up lens when wishing to image modern high density PCB’s. Spotting the exact location of a hot MLCC on a high component density PCB can be challenging at a distance (IPA on the area will often reveal the failed component though). Close-up lenses are cheap and easy to construct, so why not have on on the bench ?

Price : This is very much influenced by the intended use of the camera and wealth of the user. A hobbyist can likely ‘make-do’ with a 120x90 pixel UTI-260A cameras and will not have to pay a fortune for it. A user wishing to use thermal imaging in a commercial scenario will be better served to buy a higher resolution camera that provides good, clear images for easy interpretation. This aids speed of use and makes the imaging more pleasant. A decent 320x240 pixel camera would serve such a person well and pay for itself quickly with faster PCB diagnostic times. Shorted components/tracks on laptop PCB’s can take seconds to find, rather than many minutes, or even hours. In a commercial setting I advise users to buy the best that they can justify and afford. It may even be a deductible against TAX ?

Well I think I will close here. This thread took me a long time to write as I tend to “write as I speak” so texts can be verbose. Reading my posts can be a bit like reading a story book  Anyway, if this thread helps just one person to navigate the confusing world of thermal imaging camera specifications, it will have been worth the effort.

Fraser

[mzzj]

Manual setting of centre temperature and span is a very useful feature that is sadly often lacking on budget thermal cameras as manufacturers seem to want the camera to configure itself for best imagery so that they are easy to use. Providing a full manual mode costs nothing but risks inexperienced users configuring the camera poorly and believing that it has an issue.

For reference: Best listing of manual span -capable budged cameras I have found: https://www.eevblog.com/forum/thermal-imaging/budget-thermal-imaging-camera/msg5237088/#msg5237088

Guide PC210 seem like cheapest budget camera that has manual span and level.

[artag]

Sadly it appears that there is not much interest in adding real World pictures to this thread. People have very busy lives these days so I totally understand. Sadly I have no more spare time to populate this thread with pictures from cameras in my collection (it takes time to set up and capture useful images). I hope that the written content of this thread will be of some use to those venturing into the World of PCB thermal imaging. The thermal camera can be a very useful tool for understanding what is happening on a faulty PCB or power supply…. a real time saver in many cases. It is not the panacea for all PCB faults though….only those where a heat signature can tell you something useful about the fault.

Thanks for your efforts in writing this up. There's a lot to read and I haven't absorbed it all yet but I appreciate it and do intend to add some pictures when I can.

[chrono68]

EDIT - Added shots in standard mode.

HIKMICRO PocketC w/ 0.12x Macro Lens (Same as Pocket 2 but no Wifi connectivity):


Image is of a knock-off Arduino Pro Micro.

Amazon Link:
https://www.amazon.com/HIKMICRO-Thermal-Imaging-Resolution-4%C2%B0F-752%C2%B0F/dp/B0CL6JNF2X/

Micro Lens Link:
https://www.amazon.com/HIKMICRO-Thermal-Imaging-Pocket1-Pocket2/dp/B0BHP17WX1/

Pros:
Can manual adjust the top and bottom range on the handheld or in their post processing software.
Post Processing software is a clone of FLIRs and works very well.
Macro Lens gets REALLY close, so an unwanted hot part doesn't "drown out" what you're looking at.
Very good resolution in standard mode.

Cons:
Bit Pricey when you include the macro lens and there's no coupon code active.
Macro Lens can be too close sometimes (Can't even fit an entire Arduino Pro Micro in the shot).
Resolution in Macro Mode can be a bit grainy.

[Hazel]

Hello.May I ask what is the resolution of a thermal imaging camera commonly used for PCB inspection? I am a machine vision manufacturer from China, recently my customer bought 1280x1024 resolution thermal imaging camera from me for electronics repair, but 1280 resolution thermal imaging camera is very expensive. I was wondering if such a high resolution is necessary?