How to create small (mK) temp differences to test cameras? - Page 1
Forum section: electronics / general

author: Ultrapurple
author_rank: Super Contributor
timestamp: April 08, 2019, 06:41:10 pm
content: I have a number of cameras that claim various degrees of sensitivity, going down to a NETD of 30mK. How might I go about arranging some sort of test rig to check these claims? I have visions of terribly high accuracy, but realise there may be much simpler methods using, say, samples of different emissivities.How to proceed, without spending a fortune I could better invest in more thermotoys?

author: Fraser
author_rank: Super Contributor
timestamp: April 08, 2019, 09:03:14 pm
content: Bill W will know but I will look in one of my reference books on testing cameras and see what is used for the test. Be aware that the NETD spec is often less than perfect as it does not include the lens performance.Fraser

author: Fraser
author_rank: Super Contributor
timestamp: April 08, 2019, 10:21:03 pm
content: OK, I have checked my reference books.You really want to be measuring Minimum Resolvable Temperature Difference (MRTD) and Minimum Detectable Temperature Difference (MDTD). NETD can be very misleading !Carrying out MRTD and MDTD measurements involves mounting the camera on a turntable with it aimed at a Collimator that is illuminated by a MRTD or MDTD target plate via a plane mirror. A high emissivity source sits behind the target plate and this creates the required accurate temperature differential between the target plate and itself for the tests.The collimator is used to permit cameras that cannot focus on close targets to be tested. If a camera has close focus capability, the Target may be imaged directly without the mirror and collimatorI will see if I can capture a picture of gene relevant page and upload it here.Fraser

author: Fraser
author_rank: Super Contributor
timestamp: April 08, 2019, 10:38:10 pm
content: Crude photographic captures from the book "Thermal Imaging Cameras - Characteristics and Performance"By Thomas L. WilliamsAll rights acknowledged and respected. This is a very good book for those wishing to delve deeper into thermal camera testing methods and specifications. I bought my used copies for around £40 each. Not cheap, but then specialist books rarely are !From the measurement techniques detailed you may be able to create your own version of the tests to achieve what you desire. Sadly you are likely to only be able to determine the differences in performance between different cameras in your collection though. Truly accurate measurements do require specialist equipment. Then again, if you are willing to put the effort in, you could replicate the test equipment, as detailed below......The performance will depend upon the controller quality and build of the emission plate and associated Peltier driver.You will see that a key element of the MRTD/MDTD tests is the target plate (that often sits at ambient temperature) and the black body source that sits behind it. The black body source and target plate may be coated with the same paint to produce the same emissivity. It is then a case of building a temperature controller for the black body driver that monitors the temperature of the target plate and block body emission plate. The controller may then set the drive to the black body plate so that it presents a small temperature differential to the measured temperature of the target plate. The black body plate is viewed through the target plate slots and the camera tries to image the slots. The temperature sensors should be decent quality, such as PT100 RTD's and as both positive and negative temperature differentials are desired, a Peltier element could be used to heat and cool the black body emission plate. the sort of Peltier module commonly used in mini fridges would be ideal. the Peltier driver is ideally a PWM type rather than simple cyclic on/off switching but this is not essential. The controller should be capable of reversing the polarity of the drive as required to set the temperature and maintain it. A common 'H' bridge driver is usually used for this reason. the actual temperature controller can be a commercial product that has a temperature offset capability or one could be constructed using an Arduino. This would be a fun project that would also provide a decent Black Body temperature reference for other uses. It is the sort of thing I used to do many years ago for funSadly I rarely get to complete such projects these days.Fraser

author: Fraser
author_rank: Super Contributor
timestamp: April 08, 2019, 11:13:07 pm
content: For the Peltier heating and cooling assembly, you can use the commonly available mini fridge units. These provide the large Peltier element, heatsink and fan. They cost between £10 and £20 depending on whether you buy from China or the UK. The smaller heatsink and fan is intended to be the fridge cooler element but you would ditch this in favour of a nice piece of 5mm thick aluminium sheet that is painted with a relatively high emissivity spray paint. Many matte black enamel or camouflage paints will work well. VHT matte black is also good, but expensive.https://www.ebay.co.uk/itm/Thermoelectric-Refrigeration-Semiconductor-Air-Conditioner-Cooler-Kit-2-S400/113156487481?hash=item1a58a6f939:m:mBxJ5244zFz68mjVU60BxXgThe power supply for the Peltier element needs to be quite beefy so think about buying one of the common Chinese SMPSU 'blocks that provide 12V at lots of AmperesThey are very cheap and my experience of them to date has been good. They are commonly sold for driving high current LED arrays.https://www.ebay.co.uk/itm/DC12V-for-LED-Strip-Light-LED-Power-Supply-Transformer-IP20-AC-230V-UK-Lighting/122256974985?hash=item1c77156489:m:m0_pbBs4Ap627_9RC4vY2MAThe challenge will be the Peltier controller and driver. Many simple Chinese controllers are on/off cycling types with no 'H' Bridge polarity output and likely no temperature offset capability. I will leave that to you to investigate. Suitable 'H' bridge drivers for the Peltier are quite common in the Arduino world for driving motors in robots etc. so no problems finding those from China at affordable prices.https://www.ebay.co.uk/itm/Dual-Motor-Driver-Module-Board-H-Bridge-DC-MOSFET-IRF3205-3-36V-10A-Peak-30A-FG/143037334929?epid=517897261&hash=item214db08591:g:ZwoAAOSw9PlcBHLqThis is the common, and quite crude' Peltier controller that comes out of China at low cost.....https://www.ebay.co.uk/itm/WH7016K-Digital-Semiconductor-Temperature-Controller-Thermostat-Peltier-DC-12V/323542365018?hash=item4b54a0b35a:g:eAkAAOSwsDZb5lhiIt would need adaption for this application.There are Arduino projects to create a TEC on the internet. They are quite simple but may be the basis of a decent Peltier controller.This is sounding like a fun little project to undertake. I should create a DIY Black Body kit for thermal camera hobbyistsFraser

author: Fraser
author_rank: Super Contributor
timestamp: April 08, 2019, 11:33:00 pm
content: A typical MRTD target is shown here:http://www.digital-abode.com/blackbody/mrtd.phpSuch need not be so complicated for some basic tests and may be fabricated from a thin sheet of aluminium by marking it out and cutting suitable slots in it. then paint it with high emissivity paint as already stated.Fraser

author: yertle
author_rank: Newbie
timestamp: April 08, 2019, 11:41:01 pm
content: MRTD is traditionally defined with a person in the middle. The observer uses their eye to notate when they can barely distinguish the foreground and background (4 bar target), I think on both sides of the delta (background hotter and background colder), and then with various frequency targets.With that said, I don't generally regard this as a great scientific test. NETD will help find your noise floor, and does not require a collimator or 4-bar targets.EDIT: oh yeah, and to run NETD you can get by with a blackbody you can set to 2 temperatures, or 2 blackbodies in the same scene. You need to know the temperature of each. I think that's the minimum hardware.

author: Fraser
author_rank: Super Contributor
timestamp: April 09, 2019, 09:06:53 am
content: @Yertle,Fair comment. I am just used to NETD being a somewhat abused specification used by marketing teams in an attempt to make their cameras appear better than the competition. From that perspective it has been somewhat discredited in my mindDone properly and honestly, NETD is indeed a reliable specification with which to compare camera systems.I do like ‘real world’ tests that basically tell the user what they will witness in daily use. MRTD is, after all, a real world test of what a user sees when actually using an equipment. From that perspective, I do believe it to be a valid test of the COMPLETE camera system including the display. A non optimal LCD display can effect a cameras performance from the users standpoint. This is well worth capturing as some users will use the camera in local display mode rather than with a PC and analysis software. Excellent sensor NETD does you no good if the lens and display system are not up to the required specification to make best use of itFraser

author: Fraser
author_rank: Super Contributor
timestamp: April 09, 2019, 11:27:04 am
content: On the TEC controller front, I just ordered one of these to play with.....https://www.ebay.co.uk/itm/DC-12V-TEC-Semiconductor-Cooler-Automatic-Thermostat-Temperature-Controller/333105045378?_trkparms=aid%3D111001%26algo%3DREC.SEED%26ao%3D1%26asc%3D56113%26meid%3Ddd5661b0d2c642e3a8be24e660732ddf%26pid%3D100675%26rk%3D3%26rkt%3D15%26sd%3D264275719301%26itm%3D333105045378&_trksid=p2481888.c100675.m4236&_trkparms=pageci%3Ab39ed010-5ab9-11e9-97be-74dbd180c2e7%7Cparentrq%3A01d5676c16a0a99b2e29f7defffdc92b%7Ciid%3A1It is crude but at £10 I thought I would take a look at it. I already have a large Peltier module from a wine chilling cabinet to use with it. Temperature resolution of 0.1C is enough for making a simple black body but it will be interesting to see how well the controller manages the mission plate temperature. This is not a PWM controller. It uses relates for polarity and drive on/off.Fraser

author: Fraser
author_rank: Super Contributor
timestamp: April 09, 2019, 11:52:54 am
content: I made a £50 offer on an Aurora Scientific 825A TEC controller and it was just acceptedThese units are used in laboratory experiments to precisely control experiment temperatures using a water cooled Peltier module. It looks an excellent controller for a nice Black Body referenceIt uses an analogue devices AD590KH precision temperature sensor in the control loop and also provides a Thermocouple ‘spot’ temperature measurement facilityI have just ordered the precision temperature sensor (£9.50) and a T type thermocouple (£3.50). The controller is capable of ‘smart’ driving any common 12V Peltier module so is perfect for the task.Fraser

author: yertle
author_rank: Newbie
timestamp: April 09, 2019, 02:32:42 pm
content: Agreed!

author: Ultrapurple
author_rank: Super Contributor
timestamp: April 09, 2019, 02:56:48 pm
content: Quote from: Fraser on April 09, 2019, 09:06:53 amAbsolutely agreed.I have recently been stunned by the image quality I'm getting from my Therm-App Pro now I've popped the 13mm f/1.0 lens back on. Unfortunately the lens' image circle doesn't quite cover the sensor, meaning that the corners are distorted / blank (depending on focus setting; as the lens moves closer or further from the sensor the image circle shrinks and grows respectively). Given a room that has been undisturbed for long enough for its contents to reach thermal equilibrium, itstillproduces nice, contrasty images.It is because of this that I want to see about making some sort of repeatable measure of camera sensitivity. I recently did a thoroughly unscientificside-by-side comparisonof my Therm-App Pro and FLIR SC660 and was surprised how the Therm-App appears more sensitive and contrasty in low thermal span circumstances. (As I mention in my posts, I do appreciate I'm not really comparing like with like because the FLIR is a far more sophisticated, and stable, device). In theory the Therm-App Pro has a NETD of 30mK and, depending on what specs you read, the FLIR SC660 with 24° lens is either 50 or 30mK (anyone know for sure?).Thanks to Bill I now have a rather nice 18mm f/0.7 lens to try with the Therm-App Pro. As yet I don't know whether it's physically compatible (in terms of back-focus distance) but I will report back; all being well it should blow the stock 19mm f/1.2 lens out of the water. Again it's something I'd like to be able to quantify, hence the original question in this post.

author: Fraser
author_rank: Super Contributor
timestamp: April 10, 2019, 10:07:39 am
content: I have found some excellent compact Peltier units that include a high efficiency heat sink and fan and are perfect for building a DIY Black Body. These save you the challenge of building a neAt heatsink assembly and heat/cool plate and are intended for use in scientific equipment. The Peltier element is a high quality item that was designed for the application. Likely better quality than the many clone 12706 elements found on eBay. The cost ? Just £15 eachThese are a real bargain as they normally retail at around $400.https://www.ebay.co.uk/itm/Peltier-Thermoelectric-Cooler-Module/292812570594?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649Interactive datasheet......https://www.lairdthermal.com/thermal-wizard/thermal-wizard-thermoelectric-assemblies-datasheetThe units were made by SUPERCOOL of Sweden but they have become Laird now. Data sheets and specs are available. This little heater/cooler would make an excellent basis for a black body reference. The heat/coolplate could be painted and used directly, or it could be attached to a larger heat spreader plate if desired.This datasheet is the closest to the SUPERCOOL unit under the Laird range....https://www.lairdthermal.com/sites/all/modules/thermal/thermal/images/tea/Tunnel%20Series/DA-033-12-02/DA-033-12-02-datasheet.pdfLaird catalogue......https://assets.lairdtech.com/home/brandworld/files/ETS-BRO-Thermoelectric-Assemblies.pdfFraser

author: Ultrapurple
author_rank: Super Contributor
timestamp: April 10, 2019, 01:53:27 pm
content: Quote from: Fraser on April 10, 2019, 10:07:39 amThanks - they look interesting. I've ordered a couple. Even if they're not suitable for setting up as a thermal test rig they may well be useful as a desktop drinks cooler.

author: bugi
author_rank: Regular Contributor
timestamp: April 10, 2019, 02:30:04 pm
content: Quote from: Ultrapurple on April 10, 2019, 01:53:27 pmConsidering that the seller mentions "We used these to cool 125ml bottles of water from room temp to near freezing." it should indeed do as drink cooler ;PTempted me, too, but what a pity, ebay.co.uk... the place where half the (non-chinese) sellers outright do not ship to Finland, quarter of the rest might after discussions, and with the uncertainty of whether or not it will be across customs border in few days.. (I have no trouble paying the customs/VAT, but when payment would happen with the current price including (UK) VAT, and when/if brexit happens before delivery, I might need to pay another (local) VAT when the item finally appears in Finland or at least do more paperwork, etc. etc. Better wait until it gets clear, if ever.)Had a small laugh on the "Patent pending: YES" on the label

author: Fraser
author_rank: Super Contributor
timestamp: April 10, 2019, 02:55:41 pm
content: They are very neat and refined units and what resides inside my ISOTECH 980 is basically the same design with an H bridge and Peltier PID driving it. We all know how much a decent black body reference costsA DIY unit is definitely possible but the challenge is usually finding a decent Peltier assembly and controller for it. The controller remains a challenge as I have yet to find a cheap, but effective, controller on eBay. Used Commercial units like the one I modified for my BB150 are available, but still expensive.Fraser

author: Fraser
author_rank: Super Contributor
timestamp: April 10, 2019, 03:02:35 pm
content: Bugi,Yes I laughed at the Patent Pending entry as well 😄With regard to Brexit...... it is a mess but because of that I very much doubt you will be effected by it if you bought one of these coolers. Not sure about Finland but UK allows £15 of goods to enter from outside the EU VAT free. I do not see Brexit being a quick change in boarder rules as too many have too much to lose.These coolers are things of beauty compared to the cheaply constructed Chinese offerings with their Peltier modules of unknown quality. Peltier modules in a black body need to be decent quality to tolerate the thermal cycling to different temperatures and high temperature differentials. The Supercool/Laird units appear decent and the retail price on Digikey is eye watering ! US$300 +Taxhttps://www.digikey.com/product-detail/en/laird-thermal-systems-inc/DA-033-12-02-00-00/926-1071-ND/2269626Fraser

author: Fraser
author_rank: Super Contributor
timestamp: April 10, 2019, 03:38:45 pm
content: For non UK purchasers, let the seller know you are from the EEVBlog forum where they have been mentioned and he may be willing to ship to you when otherwise he might not. I have advised the seller that he may receive orders from EEVBlog members. I have no connection with the seller or the products that he is selling. They are just too good a deal to miss !Fraser

author: bugi
author_rank: Regular Contributor
timestamp: April 10, 2019, 03:44:56 pm
content: Quote from: Fraser on April 10, 2019, 03:02:35 pmProblem is, once you add shipping costs, it likely gets over the 22€ (IIRC) limit, so VAT would be applied. Well, even if the shipment was another ~17.5€, 24% VAT from the total would be about 8.35€, so not a wallet emptier really, but if the carrier is one those greedy ones who want to extort 40€ or something silly for doing the 1 minute customs paperwork... (Customs limit was, IIRC somewhere above 100€, so that tiny thing won't matter anyway.)Also, assuming the appropriate people along the way do their work as expected (i.e. following the rules etc.), they _have_ to carry the customs process through, or they themselves would be breaking the laws. There has been plenty of talk about this in the news; at least hard brexit would mean UK would be treated pretty much like any other developed non-EU country, except it would have no trade-agreements.However, there might be some clauses especially for this kind of transition period to prevent double-taxes, but, ... it is not uncommon for the various government offices to interpret unclear cases to the side which benefits the government more; the worker doing such mistake won't be penalized on erring on the "safe side" (for government). The poor citizen is left to fight it back, etc.I was about to comment that the seller has solved my temptation issue, anyway, but I ended up asking just in case...Edit: just came to my mind to mention use cases. Not only also to test a thermal camera (coming hopefully Soon(tm), though apparently not yet even shipped), but I have couple projects where good temperature control is part of the design. This thing might help when testing circuit prototypes, although the final versions will need different thermal designs.

author: Fraser
author_rank: Super Contributor
timestamp: April 10, 2019, 04:18:05 pm
content: Bugi,Indeed, a decent Peltier module has many uses. The fact that they can heat as well as cool beats a resistive heater in some roles and where fast transition from one temperature to another is required, the Peltier performs well. It can heat up quickly but it can also ‘Drive’ the temperature back down quickly rather than the user having to wait for natural or fan cooling to reduce the temperature to the desired level. My Agema 1010 black bogey uses a FPC type heating element to heat its emission plate and a variable speed fan is used to provide cooling. As such the 1010 can only produce temperatures above ambient and is quite slow to cool to lower temperatures from a high temperature setting. My ISOTECH 980 will quickly increase the temperature of the emission p,ate with the Peltier module and will just as quickly lower the temperature of the plate using the same Peltier moduleThe temperature is rapidly changed and then as the target temperature is approached the controller alternates between heating and cooling until the correct temperature is achieved and maintained. There is very little overshoot on initial setting. The controller uses PWM to drive the Peltier element and keeps the emission Plate temperature spot on the setting.The joy of the detailed Supercooler unit is its ensign. It is a complete self contained emission plate, Peltier element, heatsink and fan, all in a neat package, ready to be attached to a larger emission plate or apparatus. These make neat water coolers and heaters as well. You just add a small metal water tank to the emission plate (£3 on eBay for PC use) and pump the water/fluids through it. Such a system is used to pre-chill cooling water that is pumped through my Israeli BB150 Black Body heatsink so that it can achieve -40C at the emission plate.Fraser

author: Max Planck
author_rank: Regular Contributor
timestamp: April 10, 2019, 05:57:26 pm
content: I think we should start with what is NETD. Even if it is called "thermal sensitivity" (or "temperature resolution", or etc.) it is in fact a parameter describing the noise level of a thermographic system (Noise Equivalent Temperature Difference). By definition, as per ASTM E1543 – 14 standard, it is defined as the minimum detector input signal (temperature difference between the background and the target object) at which a signal to noise ratio equal to 1 is obtained in the output image signal.One should add, that the standard is for single pixel scanned systems and today there is no single, general standard for NETD measurements. Every manufacturer can have its own way.Long story short, there can be a temporal NETD, a spatial NETD or a spatio-temporal (i.e. 3D) NETD.The simplest way to measure it is to record a series of images - say 500 - of blackbody set to a temperature slightly above ambient. ASTM E1543 – 14 advises 7-8 degC above and ambient 22 degC. The basic idea is to avoid the influence of convection. After recording the series, one has to calculate the temperature measurement standard deviation for every pixel. If plotting the histogram of those standard deviation values for every pixel, one should get normal distribution. The final step is to calculate the mean value and standard deviation of that distribution. Finally, NETD can be assumed as equal to the mean value (the most probable value of the normal distribution above) or for example the mean value + 2*standard deviation. In the latter case it means that rougly 95% of the FPA pixels will exhibit a noise level below the calculated NETD. The final result in this case is a spatio-temporal NETD.One should also note that there are several factors affecting NETD for a given camera like integration time or the lens. For example for uncooled systems, unless otherwise stated, the NETD in the datasheets is given for a F/1 lens. The darker the lens, the higher will be the real NETD value.So, no need for mK controlled heat source.Fraser,the USAF 1951 target is for image intensifiers testing and not for MRTD. MRTD uses a 4-slot target.Max

author: Ultrapurple
author_rank: Super Contributor
timestamp: April 15, 2019, 09:48:23 am
content: Quote from: Ultrapurple on April 10, 2019, 01:53:27 pmMine arrived this morning. Very nicely made, but there is no thermal control of any kind. The PCB is merely a transition between the fan / Peltier connections and the screw terminals. The casing to the left is a plastic shroud that keeps the cooling air in along the length of the heatsink.There is no thermocouple, thermistor or anything for temperature sensing.The Seller didn't promise anything else so there we are.

author: Fraser
author_rank: Super Contributor
timestamp: April 15, 2019, 10:13:19 am
content: Hi Ultaviolet,Sorry I thought you knew that. These are the Peltier head only, hence my comments about needing to source a controller. This module generates the cooling for a device or chamber and the temperature feedback sensor should be provided at the cooled device interface it within the chamber. Attaching a sensor directly to the chiller plate can produce false temperature data, especially when cooling a chamber. Hence why no sensor is attached to the module. The choice of temperature sensor is also very much dependant upon the designers needs for temperature accuracy and speed of response. PT100 RTD’s are common in scientific applications due to their excellent characteristics. Thermocouples come next in line, with thermistors coming a relatively poor third.What you have is a very nicely constructed and efficient cooling (or heating) head that incorporates the essential heat sinking and fan cooling needed for the Peltier to work against. The other thing to remember is that these are high quality units that use a really good quality Peltier element. Such are not cheap and you have the benefit of it being professionally mounted to the heat sink and cooling block ready for useI hope you are not too disappointed that the unit does not include a temperature controller. There are options for such from China though I have yet to find one that is a nice cased PID that can automatically reverse drive polarity for both heating and cooling. The common unit is mono polarity so you would need a polarity reversal switch to change from heating to cooling. They cost around £16. May be worth a try ? The temperature sensor is Thermistor though, not my first choice. I continue to hunt for better controllers at wallet friendly prices.Fraser

author: Ultrapurple
author_rank: Super Contributor
timestamp: April 15, 2019, 11:00:28 am
content: Thanks FraserTo a certain extent it may prove possible to use manual control. What I have in mind is that ina controlled lab environmentthe kitchen one has an air temperature that is relatively stable over any short period of time. Maintaining a reasonably small temperature differential between that and the cold/hot plate shouldn't be too difficult if one simply feeds a constant current into the Peltier device. If a temperature differential is required between the two plates then it may be possible to arrange by putting the Peltier coolers in series and shunting one. Resistors are nice and easy, and work in limited circumstances.Other than that, a pair of good-quality coolers is useful. As we're talking about small temperature differences I doubt whether two thermistors would be sufficiently alike, but it wouldn't be too hard to contrive some sort of differential control using a pair of thermocouples. I have in mind a simple differential amplifier arrangement of some thought. I will think about it.

author: Fraser
author_rank: Super Contributor
timestamp: April 15, 2019, 03:16:01 pm
content: My coolers arrived today as wellI must say I am very pleased with the build quality, especially at £15 each. These will serve my Peltier cooler/heater needs for quite some timeFor anyone wanting to know the dimensions, they are on the datasheets that I have already referenced.Fraser

author: Max Planck
author_rank: Regular Contributor
timestamp: April 15, 2019, 06:49:21 pm
content: Quote from: Fraser on April 08, 2019, 10:38:10 pmI can not agree. MRTD is not a single numerical value, but a curve (MRTD vs cycle/mrad) limited on one side by the camera IFOV and on the other side by the system noise (which can be described using NETD). NETD remains the best solution.An example of MRTD:http://publications.drdo.gov.in/ojs/index.php/dsj/article/download/12078/6319/Max

author: Fraser
author_rank: Super Contributor
timestamp: April 15, 2019, 07:31:50 pm
content: The question was how to compare manufacturers claimed NETD figures. My reply was in direct response to that request. Stated NETD in a specification sheet has been discredited to some extent by marketing teams who abuse it as a specification. If a user wishes to compare the real world performance of several cameras that they own rather than just believe potentially manipulated NETD figures, MRTD and MDTD are valid tests for the user.I have absolutely no doubt that NETD, carried out with transparency and honesty, is a valid and accurate indicator of a cameras noise floor. Sadly experience has shown that some manufacturers marketing teams just see NETD as a way to confuse, and in some cases, mislead customers. A simple question must be asked of the manufacturer..... what lens and bias settings were used for the NETD test and is that same specification as used on the product sold to the customer ? I have also known cameras to be fine tuned to achieve best NETD when the production models are not fine tuned to the same degree. On the specification sheet some impressive NETD figures can be present, whether the same performance can be achieved by the user with their camera is a different matter.I am not arguing against NETD, just highlighting to Ultraviolet that just because one camera claims superior NETD, does not necessarily mean it is better in the real world than a camera declaring a slightly higher (honest) NETD.Anyway, I have said my piece. Whether NETD, MRTD or MDTD is used, what is important to the user in a comparison of different cameras is the quality of image produced in challenging conditions of low thermal contrast in a sceneFraser

author: Max Planck
author_rank: Regular Contributor
timestamp: April 15, 2019, 08:23:11 pm
content: Sorry, but the question was:Quote from: Ultrapurple on April 08, 2019, 06:41:10 pmAs I understand, it was about a user personally testing/comparing different cameras. Thus, whatever the manufacturers are doing or claiming is irrelevant here.I also explained why your suggestion of using MRTD is not a good idea. This was just scratching the surface of the problems related to this parameter.I one uses the same method of NETD measurement for all tested cameras and is aware of the camera settings that could affect the results, it remains a much easier solution to campare a single NETD value than comparing MRTD curves.Max

author: Ultrapurple
author_rank: Super Contributor
timestamp: April 16, 2019, 07:21:43 am
content: As OP, I think the fault is mine for (ab)using terms somewhat loosely.I fully recognise that there are a number of ways of characterising a system's merit and that these have different, valid uses.What I'm actually looking for is a way of comparing two or more thermal cameras' response to small temperature differences - what I'd call 'sensitivity' - around room temperature. Although I have a technical background my main interest here lies in the artistic rather than scientific direction. Being able to see two slightly different shades of onscreen pink is more important than knowing the actual temperatures they represent, or for that matter the absolute temperatures.So, I apologise for my loose phrasing. But I am grateful for all the learned opinions and technical details that have been put forth and grateful also to all those whose ongoing help increases my understanding.

author: Fraser
author_rank: Super Contributor
timestamp: April 16, 2019, 11:43:08 am
content: The Aurora Scientific Inc 825A TEC controller arrived today. It is every bit as good as I had hoped. It appears to have either seen little use or has been in a clean environment and well cared for. I intend to drive one of the Supercool Peltier heads with it. The rear panel has a power output socket to drive the Peltier cooling fan or a fluid coolant pump so I have the required 12V for the Supercools's built in fanI have the required AD590 temperature sensor and just need to decide upon a cavity design into which I will install the Peltier emission plateI also have a couple of the high emission Black Body plates that came with the FLIR SC4000 so may use one of them with the Peltier head. I have 4 of the Peltier heads so could even build different Black Body cavities to suit different tasks. I am already in contact with Aurora Scientific Inc regarding possible modification of the units maximum settable temperature. It currently offers 0C to +40C. The separate T type Thermocouple measurement capability covers -50C to +50CUltrapurple, keep your eyes open for TEC controllers on eBay. They come up now and again at good prices. The 825A cost me £50 and is a lovely bit of kit intended for medical science lab use. It is well designed and built. See attached pictures.Fraser

author: bugi
author_rank: Regular Contributor
timestamp: April 16, 2019, 01:45:11 pm
content: My one supercooler unit should be on the way now, too, comes whenever.I was thinking either trying DIY control - pt100, misc, MCU with ADC, discrete FETs or if I happen to have some nice driver IC, etc. - or MAX1978 - expensive chip in quite a non-hobbyist package (0.5mm pitch TQFN exposed pad), but contains pretty much everything except the sensor and filtering passives. I do already have some semi-cheap chinese thing stuffed somewhere to try, but I don't even remember its ratings, might not even be suitable for driving TECs nicely.Also, the"thermal camera (coming hopefully Soon(tm), though apparently not yet even shipped)"came yesterday. The seller just hadn't bothered to notify me about the shipping.

author: Fraser
author_rank: Super Contributor
timestamp: April 16, 2019, 02:02:16 pm
content: Bugi,I am pleased that you ordered a Supercooler. I do not think you will be disappointedWith regard to driving the Peltier element, a relatively inexpensive controller may be built using cheap Arduino UNO plus an Arduino motor driver H bridge board. The Peltier element is rated at 12V 3A so not a huge current involved. A Google search on Arduino TEC or Peltier controller should bring up other experimenters experiences with such. You can drive the Peltier in simple on/off and polarity mode. This is what many Peltier refrigerator controllers do. Refrigerator controllers are normally limited in accuracy and offer only single polarity drive for cooling, so not much use to us here.Fraser

author: Fraser
author_rank: Super Contributor
timestamp: April 16, 2019, 03:00:26 pm
content: Bugi,If you do not mind saying, what thermal camera did you buy ?Fraser

author: bugi
author_rank: Regular Contributor
timestamp: April 16, 2019, 03:22:06 pm
content: TE-Q1 "large kit". Which, if I have understood it correctly, includes the same body used for both TE-Q1 and TE-Q1 plus, and both the respective lenses. And accessories and SDK. I wouldn't have needed the extras (I've got enough various similar accessories from other stuff already), but the SDK will get into use, sooner or later.I did look for higher frame rate cameras, but either they seemed to be too much hazzle and/or price jumps a lot and/or seemed to be noisier and/or lower resolution. That TE-Q1 should be enough for most of my use cases; only two (of my current) ideas would benefit directly from higher framerates, and neither idea is anywhere near the top priority in my project list.So far I've only quick-tested it last night, i.e. few minutes of looking random things with old galaxy S5 as host, just to check that it works properly. I'll probably do a bit more testing and reading through the manuals etc. this evening. And probably start wondering about "black bodies" and known temperatures much later, probably next summer, when I might have some time to dig into the SDK and hack up some DSP. Having some time is likely wishful thinking, considering all the other projects queued up, but...Edit: related to this particular topic, couple of them projects include keeping temperature gradients minimized on electronics (and with their inner containers), so sub-kelvin differences would be nice to see, one way or other.

author: Fraser
author_rank: Super Contributor
timestamp: April 16, 2019, 03:33:27 pm
content: Good purchase choiceFraser

author: olivir
author_rank: Newbie
timestamp: April 16, 2019, 03:50:28 pm
content: A comment on NEDT, there is a relationship between NEDT and dynamic range. It is possible to tweak a camera for better NEDT by increasing responsivity of the detector. This is done by increasing bias in uncooled detectors or integration time in cooled detectors. The price to be paid here in practical terms is a reduction in the maximum temperature that can be imaged without saturation. When comparing NEDT specs it's good to know what temperature range can be imaged. The same thing happens with F number. If you take two identical cameras and install an F1.4 lens on one and an F1 lens on the other, the F1 camera will have a better NEDT (by a factor of 2 for uncooled cameras) but will saturate at a lower scene temperature.

author: Ultrapurple
author_rank: Super Contributor
timestamp: April 18, 2019, 11:59:04 am
content: Quote from: olivir on April 16, 2019, 03:50:28 pmVery good points. I remember hearing some time ago that the Ulis sensor in the Therm-App had been tweaked (biased) for minimum NETD and it really is rather good in day to day use. But, as my recent comparison with the FLIR SC660 demonstrated, it falls right over when given a particularly hot scene, precisely what you're saying.On the whole I like the greater sensitivity but, as I've noted many times, I play with thermal imaging for the pretty pictures rather than the diagnostic science.

author: Bill W
author_rank: Super Contributor
timestamp: April 18, 2019, 10:19:28 pm
content: Quote from: olivir on April 16, 2019, 03:50:28 pmAgreed, although NETD should only be measured at the sensor, which is both the strength and weakness of it as a camera figure of meritQuote from: olivir on April 16, 2019, 03:50:28 pmSorry, but no. NETD should always be measured at f/1, even if the camera is not.As many camera manufacturers are clueless they just paste the detector supplier NETD in and call it anything they like (sensitivity etc) even when it is notThat is where MDTD (zero frequency MRTD) is useful even though it often uses a human observer. That then includes the real lens, all the processing, the display gamma, the display itself and finally the human eye-brain interface.It is possible to measure a camera signal to noise with a raw image grab (Image J has all the tools) and you set the standard deviation of a flat image against the signal of a few degrees differential.If you allow a 10 frame average for 'eye-brain' and a decent display you should be close to observed monochrome MDTD.The statistical approach of ImageJ can be used to compare potential gain/integration/bias combinations easily.What is actually surprising is ending up with a camera MDTD not far off the detector NETD.Bill

author: Max Planck
author_rank: Regular Contributor
timestamp: May 03, 2019, 04:06:46 pm
content: As I wrote in another thread, as per the ASTM standard, NETD is measured at the detector preamplifier output, thus taking into account the detector and preamplifier noise, neglecting the lens etc.The fact is, that today there is no universal NETD measurement standard that would be adapted to FPA based camera designs and the end user is interested in the performance of his entire camera, not just the detector or detectors in the FPA.The f/1 is a good practice - if we are talking uncooled - but not a must. It makes no sense when talking about uncooled systems.Quote from: Bill W on April 18, 2019, 10:19:28 pmNo surprise here. Please have a look at Annex A.https://books.google.pl/books?id=-ZwYxus-Y5sC&pg=PA200&lpg=PA200&dq=mdtd+camera+measurement&source=bl&ots=8glpFkxVfQ&sig=ACfU3U0mjGpNjesGEssJqMey0j9820DeyQ&hl=pl&sa=X&ved=2ahUKEwj95Zjnwt7hAhUplosKHbhvDvYQ6AEwB3oECAwQAQ#v=onepage&q=mdtd%20camera%20measurement&f=falseAs I wrote before, MRTD (and MDTD) are curves limited on one end by the camera noise and by system spatial resolution at the other. The exact numerical values will of course depend on the model/measurement method, but if the IR system/application is noise limited and we are considering not the entire curve but its lowest value, the NETD/MRTD/MDTD fuss ends anyway as NETD vs NETD vs NETD (or close to).Max

author: Bill W
author_rank: Super Contributor
timestamp: May 08, 2019, 12:45:20 pm
content: Quote from: Bill W on April 18, 2019, 10:19:28 pmQuote from: Max Planck on May 03, 2019, 04:06:46 pmAn observational MDTD will vary by a factor of 2 or 3 between colour palettes or LCD panel, when run on the same sensor/lens/biases. Your assumption of a system limited solely by the pre-amp NeTD is not the case.Equally one could make a camera with 128 field averaging and easily surpass the sensor NeTD. Useless for looking at moving things of course. Just the same as digital averaging on a scope compared to a single shot trace.Bill

author: Max Planck
author_rank: Regular Contributor
timestamp: May 08, 2019, 08:01:28 pm
content: And the point of all this is??Quote from: Bill W on May 08, 2019, 12:45:20 pmIf measured for example according to STANAGs, yes, there is a long list of factors that could have an influence on the final numerical value, including the most important one - the observer, its training, etc...If other methods are used, it is no longer the case. For example it can be calculated based on system MTF and noise data.Quote from: Bill W on May 08, 2019, 12:45:20 pmI made no such assumption. Just corrected some information provided in the thread.Quote from: Bill W on May 08, 2019, 12:45:20 pmAny manufacturer can addany type of signal/image processing, palette optimisation, etc...The thread starter asked a simple question:QuoteThe simplest answer is how to measure NETD. It is just a figure of merit like several others. Its advantage is the fact than there is no pallete, display, observer influence. Pure numerical calculations. Thus, it is easy to repeat/verify the measurements as long as the same method is used. NETD is more axed on temperature measurements, whereas MRTD curve is rather dedicated for IR observation systems.It does not mean temperature measurement with +/- NETD accuracy, but this is another story.Max

author: Bill W
author_rank: Super Contributor
timestamp: May 09, 2019, 12:02:17 pm
content: Quote from: Max Planck on May 08, 2019, 08:01:28 pmThe thread starters' premise of using a few mK temperature differential to measure NeTD is not how it is done, so in some ways the question is unanswerable.The implication that setting up a 30mK difference might mean anything to observations of a "30mK" sensor is the problem.You can only compare what you have in a consistent manner, which to an end user will mean near or at the output (video, data stream, screen, etc), which pushes you towards MDTD (ie MRTD (0) )A typical commercial NeTD experiment uses a 19" rack of equipment (16 bit cooled ADC, special sensor PCB, shielded everything, smoothed everything) to measure the sensor IC output noise, and also measuring the signal from a 29.5°C and a 30.5°C target, for all pixels.regardsBill

author: cnxunuo
author_rank: Regular Contributor
timestamp: May 11, 2019, 03:10:42 pm
content: Consider finding one of theseI got one from local electronics junk yard.

author: Fraser
author_rank: Super Contributor
timestamp: May 11, 2019, 10:39:07 pm
content: Nice Black Body. I am envious of youFraser

author: CatalinaWOW
author_rank: Super Contributor
timestamp: May 12, 2019, 03:21:09 am
content: I completely agree with Bill W's comment and will add this - all of the discussions above of the "correct" way to measure any of the many figures of merit of a system have an implicit assumption of how the system is applied. The question cannot be answered without a good understanding of that.The OP says that he merely wants good pictures of objects with a relatively small temperature range. For this he definitely is concerned about monotonicity of the system response, and is somewhat interested in linearity and has an interest in the system noise level. But might be satisfied with reducing the noise by integrating dozens or even hundreds of images. Which can be done without loss of dynamic range if the integration is done in an appropriate signal processor after the signal is digitized. But this integration will only help for truly random noise, so his figure of merit for his application will also need to pay attention to fixed pattern noise stability.The upshot of all of this is that the equipment required is not necessarily out of reach. A couple of black bodies carefully characterized for uniformity and temperature and a good computer. The truly difficult part is thinking through what matters and how to measure it to accomplish the particular purposes at hand. The answers will be very different for an art camera generating nice pictures at a few frames per day rate than it is for a surveillance system or a military IRST.

author: Max Planck
author_rank: Regular Contributor
timestamp: May 12, 2019, 07:20:32 pm
content: Quote from: CatalinaWOW on May 12, 2019, 03:21:09 amExcellent idea. Let's apply it pratically. So, what was Ultrapurple asking about? What was his camera scenario? IRST? No. A noise limited one?Let's now forget about it and have a look at IRST.Quote from: CatalinaWOW on May 12, 2019, 03:21:09 amThis time we are talking about a spatial resolution limited scenario, with the IR imager to target distance from a certain range of values. Single MRTD value - this is what was advocated all over this thread - would be again a, let's say wrong choice. MRTD curve is what is needed.By the way, I gave already examples of such curves, but given some bells and whistles hidden by some of the manufacturers inside the equipment, there could be sometimes real surprises.http://photonics.pl/PLP/index.php/letters/article/view/4-54/253Regarding equipment, a liquid based blackbody model would easily do the job. Something cheap and easy to make at home.Max

author: Bill W
author_rank: Super Contributor
timestamp: May 12, 2019, 11:14:42 pm
content: Here's an MRTD target set:http://www.sbir.com/images/Target/4BarNoTitle.jpgYou put these in front of your black body (the target stays at ambient or thereabouts) and run the black body up and down in temperature until you can just (make out) and (not make out) the bars - so four temperatures, and then for each bar set.Then average the four temperature differences.By using the black body both hotter and colder than ambient the actual temperature of the target ambient is cancelled out.MDTD is done with a 'big' square or round hole - ie zero frequency MRTD.Bill

author: cnxunuo
author_rank: Regular Contributor
timestamp: May 13, 2019, 01:14:05 am
content: diy a CNC usaf1951?

author: CatalinaWOW
author_rank: Super Contributor
timestamp: May 13, 2019, 04:09:25 am
content: When I was unable to find anything other than nth generation copies of the 1951 USAF test target I created the attached document that at least has crisp, unblurred edges on the smallest bar targets. Not traceable to anything, but good enough for local use. The warnings on page 1 are unchanged from when this was created more than a decade ago. Feel free to use it to CNC or send it off to be etched into a brass or aluminum sheet.

author: cnxunuo
author_rank: Regular Contributor
timestamp: May 13, 2019, 04:35:05 am
content: I want to try using laser stainless stensil service from pcb manufacturers and spray a black body paint over it, but unfortunately I am no longer in china...need to ship/carry my black body to where I live now.fitting an array of pt100 to brass plate and stick some thin ceramic heating elements to it could also work, I did a teardown of Fluke black body some years ago, it's very 'not metrology looking', hence the relatively low price from fluke when new. if pt100 says it's even, it must be enough for IR use, provided that black body paint is sprayed properly.

author: Fraser
author_rank: Super Contributor
timestamp: May 13, 2019, 11:19:53 am
content: cnxunuo,Thank you for your interesting comment on the Fluke Black Body. I have found exactly the same with AGEMA and other ‘proper’ black bodies. In British parlance, we call such construction techniques “Agricultural” in reference to farm machinery that tended to be basic, pretty ugly, engineering that just got the job done and could be easily maintained with baling twine and wireBlack Body references are not rocket science but the designs do need to consider the quality of the emission plate thermal flatness and accuracy. There are many approaches to this, as you likely know. Some BB’s use cavities whilst others, like your Fluke unit, seem to get away with just a suitably coated flat plate. Air convection currents are an issue with simple flat plate types but maybe not serious enough to effect the intended use ? I have BB references that have their thermal emission plates driven by either a simple PI heater sheet or a Peltier module. I prefer the Peltier module units as they can generate temperatures below ambient, but they are limited in terms of maximum temperature. Specialist very high temperature BB’s appear to be built like a Kiln with lots of specialist ceramic insulation required and so are harder to DIY fabricate so as not to burn your house downI would love to hear more about what you found inside the Fluke unit. It certainly “looks the part” but I always wondered what hid inside such units. The PID controller is often the key to a good design as its programming has to be capable of keeping the emission plate at an accurate temperature without too much drift. I have looked at the small BB references that are available from China and have always thought them expensive for what likely resides inside their casing. I expect to find only a PID controller, an emission plate cooling fan, an emission plate and a PI heater attached to the rear of the emission plate. Hopefully the PID controller uses a PT100 sensor but I would not be that surprised to find a thermocouple or thermistor being used ! I had hoped that China would offer cheaper units but being somewhat specialist, I suppose I can understand the pricing.Fraser

author: Fraser
author_rank: Super Contributor
timestamp: May 13, 2019, 11:25:29 am
content: For anyone interested, this is the type of heater used on the rear of the emission plate of my very expensive AGEMA Black Body reference. It is called a PI heater and is now commonly found heating build plates of 3D printers.This sort of heater has the advantage of excellent thermal spread over the contact area to produce a relatively flat thermal profile across the emission plate. These heaters come in many shapes and sizes and are inexpensive. They are also known as “Kapton heaters” in reference to the material from which they are constructed. Some come with high temperature 3M adhesive on one side to enable easy fixing to whatever needs to be heated. A great and very useful heater design for heating plates.Fraser

author: Fraser
author_rank: Super Contributor
timestamp: May 13, 2019, 03:01:44 pm
content: Regarding the original OP’s question....... I think this thread may have got a bit too ‘scientific’ in its approach to his needsI can understand what Ultrapurple was asking as I have seen great differences in thermal cameras real world imaging performance despite them having very similar specifications on paper. This is why I took the approach that I did in answering his question. Let me explain my experience of this issue from 28 years using this technology and a good many repairing it too.When I was buying industrial thermal cameras for my employer I would invite the various companies to demonstrate their products and this also gave me the opportunity to speak with the sales reps about any performance issues I noted. It was quickly clear to me that the microbolometer based cameras were unable to produce the clean low noise images of the better cooled staring array cameras when low Delta T scenes were involved. Such was not a surprise though.In 1997 I tested the AGEMA PM570 for its imaging performance. Compared to the AGEMA THV 550 cooled camera the microbolometer staring array appeared noisy and had an almost chicken mesh appearance to its images. The salesman acknowledged by observations and stated that this was a known issue that AGEMA hoped to address in later revisions of firmware and microbolometer scenes or arrays. The PM570 contained a 1st generation 320 x 240 pixel microbolometer and AGEMA were still learning how best to deal with its relatively noisy signal output. Their software engineers were tasked with taming the beast through image processing techniques.Move forwards a few years and we saw improvements in the image processing software that was used to clean up the images that the microbolometer was producing. The PM series was, by then, a FLIR product. Over the years, the PM series saw better image processing software and lower noise 2nd and 3rd generation microbolometers. By the time the PM695 was released, FLIR had mastered the taming of the noisy microbolometer and provided the user with different levels of image processing based noise reduction to suit differing scenarios. The 3rd generation microbolometer was also a less noisy sensor array and ROIC combination. I witnessed this development of the PM series cameras first hand and I have multiple examples of each generation in my collection.So to the matter at hand..... manufacturers often provide impressive specifications for a thermal cameras performance in the hope of attracting a purchased of their wares. Nothing wrong with that and it is the way of the trade, like many others. For the buyer, it is wise to consider such specifications just a guide to a cameras maximum achievable performance and not always its real world behaviour whilst in general use. A proper assessment of a cameras real world performance is wise and that is why I never ordered an Industrial thermal camera based on a paperwork exercise. I always required a demonstration and testing period in our hands before making a purchase decision. The USA Fire Brigades found that they had to do exactly the same as the cameras specifications on paper were only a small part of the story and many other aspects of a cameras design needed investigation. Any manufacturer who would not loan me a demo thermal camera did not get further consideration.When testing the various industrial thermal cameras it became very clear to me that the paper based specifications provided little indication of how well the camera performed in my chosen application and also it was clear that some camera designs were superior to others despite having the same, or very similar specifications. Did I carry out NETD tests ? No I did not. Why Not ? Well I was not using the cameras in a scientific lab and needed to test them in the real world use scenarios for which they were being purchased. Very much like the Fire Fighters scenario. I used the cameras in various test situations and assessed the image quality and accuracy that each produced for me as a user viewing the built in display. That is how the cameras would be used, so that is how they were tested. Numbers are meaningless compared to practical use in my scenario.During the many camera tests that I undertook, some side by side with others, some on their own, it became clear to me which manufacturers had mastered the art of taming the microbolometer based technology and achieved excellent thermal imaging performance. Some cameras were quite frankly appalling in their imaging performance due to the manufacturers inexperience within microbolometer or their use of building block cores that were not suitably tuned for the best imaging performance in my usage scenarios.It quickly became clear that FLIR (nee AGEMA) were masters of the image processing ! There was little to compete against FLIR at that time and they remain a manufacture of high performance thermal imaging systems that deliver on their promises. Over the years, other manufacturers have caught up on the image processing front and we are fortunate to have a good selection of thermal camera manufacturers to choose from.In my testing of thermal cameras, I tested the complete system from lens through to the display. NETD was meaningless to me if the camera proved incapable of producing the required high quality imaging in my usage scenario. Many cameras did indeed fail my testing, some badly so ! The choice of lens and the display on which the image was viewed could have a dramatic effect on the performance of the cameras during my testing. Some actually produced better images when connected to an external broadcast quality monitor, but that was still a fail as the user would not be using such a monitor in the field ! At the end of the day I needed to buy thermal cameras that the users would find ergonomic, accurate and a joy to use. It was very important that the low Delta T imaging was as good as possible with the lowest possible noise for the camera technology. Cooled imagers were the best, but Microbolometers did manage to produce acceptable images. 2 Celsius temperature spans were common in my usage scenario.So in my humble opinion, it is best to test a thermal cameras imaging performance in the real world and in the scenario in which it will be used, rather than getting too excited about some numbers on a specification sheet. Such numbers might impress some, but not me. I want real World performance as experienced by the average user.I attach a little example of a real world situation that applies to the Fluke Ti450.Fluke realised that their Ti450 user experience was lacking on the display front. The LCD panel was just not performing as well as they wished. FLUKE used a better LCD display panel in later models of the camera. The result is, from a users perspective, two cameras of the same model and specification, yet one produces better images than the other, depending upon the age of the model ! Remember, on paper they are the same camera with the same sensitivity and NETD noise performanceFraser

author: Fraser
author_rank: Super Contributor
timestamp: May 13, 2019, 04:50:01 pm
content: An interesting article on comparing thermal cameras imaging performance........https://www.ndt.net/article/ecndt2006/doc/Tu.4.6.4.pdfFraser

author: cnxunuo
author_rank: Regular Contributor
timestamp: May 13, 2019, 05:38:33 pm
content: AGEMA makes nice cameras, I once picked up an older than me scan camera, something 900, with a huge external processor and a box full of floppy, it was less noisy than my best camera at that time, the 25um photon 640. But due to its size, I ripped the cryocooler out and throwed away everything else.A simple convection finite element analysis can be made to find out how serious an impact air can be to overall uniformity. but even if it does has big enough an impact, nothing beats a 1inch thick copper plate, unless someone spray water on it before measurements...Black body paint can be use on hobbyists level temperature, eg from no condensation to 100degree c. which provides a nice uniform emissivity with low reflection. it's just a bit expensive, in China it cost around 80 GBP per spray can.

author: Fraser
author_rank: Super Contributor
timestamp: May 13, 2019, 07:33:38 pm
content: AGEMA ThermoVision 900 RIP

author: Max Planck
author_rank: Regular Contributor
timestamp: May 14, 2019, 10:00:26 pm
content: Quote from: cnxunuo on May 13, 2019, 05:38:33 pmInstead of paint it is possible to use a thin layer of microporous rubber with open pore surface, something similar to some mousepads. It does a great job as long as the temperature drop on the rubber layer is taken into account. IIIRC the French BB manufacturer, HGH, uses some kind of rubber/foam with a micropyramid surface.Quote from: Fraser on May 13, 2019, 04:50:01 pmI wonder what was the purpose of comparing MRTD curves for two IR imagers designed for complitely different tasks and thus, having a complitely different field of view/optics.Max

author: yertle
author_rank: Newbie
timestamp: May 14, 2019, 10:39:01 pm
content: You can use a spray can of Krylon from non-condensing to very hot. Should be at most hardware stores - high heat, flat black. The emissivity should be quite good.

author: Fraser
author_rank: Super Contributor
timestamp: May 14, 2019, 10:45:17 pm
content: Max,From what I read in the article it would appear that this was a comparison of a standard issue military observer thermal scope with the sort of civilian thermal camera that is normally used for Non Destructive materials testing. They are talking about active modes of NDT testing such as flash thermography. The military use thermal cameras for NDT work in their maintenance activities. If the standard issue military thermal scope was comparable to the FLIR SC3000 they were hoping to avoid buying the additional SC3000 cameras.As you say, they are very different cameras in many respects but I suspect someone made the suggestion and they decided to investigate the possibility.Fraser

author: Max Planck
author_rank: Regular Contributor
timestamp: May 15, 2019, 07:12:56 am
content: Fraser,you may be right, but for me this article is an example of what could go wrong.First of all, there is a lot of information missing.What was the intended use of the camera (just NDT is more than vague)? Sample size, distance, etc.?No technical data for both cameras, so I had to check it.FLIR SC3000LWIR QWIP 320x240 FPANETD 20 mKFOV 20˚x 15˚In fact you have a camera from the same familly.Thales SophieImage size 754 x 576LWIRWide FOV 8° x 6°NETD <50 mKBecause of the weird resolution, I made some digging and the imager is a scanned 288 x 4 MCT LWIR FPA from Sofradir. It means there is probably a digital x2 zoom with some image processing and smoothing to get the final resolution.My educated guess is that FLIR's camera wins easily in all departments as long as it gets the right lens for the intended job.As a sidenote, I also have some doubts about the final conclusions, for two reasons. The depth of the defect that can be detected is closely related to its size and NETD is not a limit if lock-in technique is used.* Again, the question about a more precise description of the intended use.* Would it be possible to use lock-in thermography? Probably yes with SC3000, probably no with Sophie.Max

author: Fraser
author_rank: Super Contributor
timestamp: May 15, 2019, 09:00:04 am
content: Max,I totally agree with you. In hindsight, whilst an interesting exercise, it was severely flawed from the start. As I say, probably someone’s idea of a ‘quick win’ to use equipment already in the inventory rather than buying the correct tool for the job. I was more interested in their approach to comparing two cameras performance though. I still found it an interesting, if flawed, testI have a FLIR SC3000 cooled Quantum Well camera in my collectionA very nice piece of thermal imaging technologyThe SC4000 is a very different beast though. The SC3000 is a development of the AGEMA Thermovision THV 550 basic design with a different sensor array. The SC4000 is based on the Indigo Phoenix cooled camera.Fraser