Black Body Thermal References and Fraser's new Black Body project :)

[Fraser]

NASA's plot if the four best performing paints. Krylon Ultra Matte Black (1602) is in the top 4 and thankfully easily purchased, unlike most specialist high Emissivity coatings.

Fraser

[Fraser]

The Nextel paint is a suede paint, as found in cameras. It has a soft plush finish ! This explains why the Matte finish works so well. Not quite what I want on a thermal emission plate though.

Fraser

[Fraser]

FLIR's comment on enhancing Emissivity........

http://www.flir.com/science/blog/details/?ID=71556

Who would hav thought that 'white out' correction fluid was useful in thermography eh ?  As the article says, the visible colour is not that important, more important is the finish. Matte is best.

Fraser

[SeanB]

Looking at your scratches you probably will have to remove the plate, strip it down to bare metal and repaint it Fraser, those scratches reveal corrosion under the paint, which will flake off the rest with time as it progresses. Probably came from condensed water containing salts, that went through the existing porous paint and attacked the underlying casting. You will be best off ( unless you are happy with the small difference in temperature in spots) stripping off all, applying a decent thin layer of chromate primer to the well sanded metal and then putting a few even coats of the matt over the primer, probably around 6 thin even coats.

[Fraser]

More comment on Krylon Ultra Matt Black

(2006)
A. The emissivity of Krylon Ultra Flat Black Paint is listed in the web site below as 0.97 at 5 um. I have recently used a 3-5 um InSb radiometric thermal imager to measure the emissivity. I sprayed the paint on a copper plate and mounted it on a cold finger of a variable temperature dewar with a calcium fluoride window. I rotated the dewar window so as to not back reflect. I measured an emissivity of 0.89 for the setup. If we exclude the reflection from the window (~0.04 x 2), this would give an emissivity for the black paint of ~0.97 in agreement with the web site.

http://www.infrared-thermography.com/training.htm

From this site.....

https://www.finishing.com/1600-1799/1670.shtml

Fraser

[Fraser]

SeanB,

Many thanks for the helpful comments.

Indeed, I was expecting to recoat the whole emission plate.

Note however that the damage was caused by rough, uncaring, handling during the disposal process 😔

The unit had not been well protected in transit to MoD auction, and to me. It had a badly deformed base plate and radiator fin as a result of being dropped. Something entered the emission aperture and scratched the paint off. I did complain to the seller that none of this was mentioned in the auction listing but he was an awkward person to deal with at the best of times. Nil response, as expected. He is an MoD auction buyer who cares not a jot about what he sells, its condition, or serviceability. He just covers himself with 'sold as seen, untested'. Not someone I would normally do business with but these thermal source heads are uncommon so 'beggars cannot be choosers'.

Fraser

[SeanB]

I would suggest for the stripping of the existing paint is to contact somebody local who can do CO2 bead blasting, as that will safely strip the existing coating off the unit, and not leave any residue either. I would also mask off the plate as well before taking it there, after stripping off all parts, and make sure to put sacrificial screws in all tapped holes, and mask off the entire area other than the areas to be blasted with some painters tape and card, using a firm grip tape so that the beads will not peel it, and at least 2 layers on the edge where it will be exposed to the beads, and probably not on the front face at all, but around the sides. A clean front with a coat of paint, hidden by the bezel is not going to be a concern.

I did the same for having heater plates recoated with a non stick coating by a local ship repair company years ago, helped though that the one guy was living next door to me in the flats at the time, and we got on well. Got a nice well blasted frosty plate back with a nice green non slip PTFE coat on it, emissivity definitely changes as you go from the oxidised rough matt aluminium extrusion to the PTFE, and it normally runs around 140C with 5 200W cylindrical heating elements in the body. Did have to do a lot of helicoil inserts though, but the existing holes were in any case well worn, the bead blasting with fine grit just finished off most of them rather well, but I was planning on doing the inserts anyway, had already ordered the inserts for the lot, simply as the stainless inserts survive heating cycles better.

Might take a spare one, with a PT100 pocket adaptor instead of the Fenwal thermoswitch, put in a PID controller and run it off 40VAC instead of mains ( slow down the ramp) and see about giving the flat face a coat of mystery emissivity Aerolac matt black as a poor man's black body, seeing as I do have a couple of them spare. Not going to win any beauty contests though for looks.

[Fraser]

Thanks SeanB

Beyond camera accuracy checks, a thermal reference can be a very useful tool to have around if experimenting with lenses, attenuators and windows

Fraser

[mahony]

Hi Fraser,
I am searching for high emissivity paint too. Seems like the nice Nextel 3101 c10 is available from a swiss company:
https://www.ibzagshop.ch/de_CH/e-shop/nextel-lackiersystem/lack/3101-nextel-suede-coating

Unfortunately the price tag is significant... 186 CHF per litre. 

Do you, or someone else have any experience with paint from those guys:
http://paints.labir.eu/

I think for my purpose this might be sufficient:
http://paints.labir.eu/paint/thermographic-paint-for-high-temperature-applications

Emissivity is claimed to be ~95+% except a small dip at 13µm. My current cheap rattle can flat black seems to be around 93 to 94% using a simple reflexion test with a hot soldering iron.

[Fraser]

Hi,

The 'official' high Emissivity coatings are expensive and hard to source, as you have found. The Nextel product is a surface coating rather than a paint. It is what you find in SLR bodies and is more of a flock coating. That is to say, it is furry ! This coating is VERY fragile and easily damaged if not protected from fingers or contact with other objects. Great for a lab, but not too practical elsewhere.

As detailed in this thread, I opted for the very Matt Krylon paint for my Black Bodies. Some other paints have very variable Emissivity characteristics across the LW thermal spectrum and at differing temperatures.

The paint you referenced looked interesting. It is the first I have seen that is easily available and claims to be specifically for high Emissivity thermal imaging applications. If you get that paint I would be interested to hear of your experiences with it.

Fraser

[Fraser]

I am in the process of ordering the LabIR high Emissivity paint for testing purposes.

Fraser

[mahony]

So am I.
Just finish testing initial testing with my Arduino/Peltier based cheapo-DIY-Blackbody. Temperature control and stability looks good now I need some black paint ... hopefully a bit better than some std. flat black.

[Fraser]

Nil response from the company today...... disappointing start.

Fraser

[mahony]

The same for me - maybe they are not interested in single can sales?
Do you have any reliable source in europe for some similar product? Otherwise I might just go with a can of Krylon Camouflage Ultra Flat Black - at least there is a German guy selling some of them on eBay...

[Spirit532]

It would be interesting to do a group buy of the Nextel 3101 C10 paint. The $187/l price is a bit painful, but think about it - how many liters of paint do you need to cover a dozen blackbody sources? It would probably end up costing ~$5-10 to cover a single emission plate of acceptable diameter.

However, it should be noted that, as per the datasheet, this is a 2-part coating that requires a thinner to make the right consistency, and a hardener to activate it.
The article numbers for those are "NEXTEL-Härter 6018"(hardener), mixed in 8 parts paint, 1 part hardener by weight, and the thinner is "NEXTEL-Verdünner 8061", of which an additional 10-15% are required for air spraying.

The coating itself is available here: https://www.ibzagshop.ch/de_CH/3101-nextel-suede-coating-14068-0015/7751
The hardener is also not very affordable: https://www.ibzagshop.ch/de_CH/e-shop/nextel-lackiersystem/haerter-verduenner/6018-nextel-haerter
The thinner has an acceptable price: https://www.ibzagshop.ch/de_CH/e-shop/nextel-lackiersystem/haerter-verduenner/8061-nextel-verduenner

[Fraser]

It is worth noting that I have yet to see a commercial blackbody thermal reference covered in the Nextel 3101 C10 coating. There is likely a very good reason for that as Such references are definitely not cheap so coating cost is unlikely the reason. All the reference sources I have seen or used looked to have a dark grey flat paint coating simikar in appearance to normal matte black chalkboard paint. I know it is more than likely the unobtainium 3M high emission paint coating though.

It would be possible to become the equivalent of a 'Voltnut' with high Emissivity coatings, but such is not necessary in thee real world. Even my most expensive industrial thermal cameras are still stated as +-2C accuracy under perfect conditions. The important factor in a reference plate is knowledge of its emission characteristics over a range of temperatures. The NASA testing has kindly provided that information for a number of paints. I am fortunate to own some very accurate spot temperature measurement and plotting equipment so I can check the temperature/emission characteristics of my references.

The classic accuracy check fir thermal cameras used at home is the 100C boiling water and 0C melting ice in water test. These provide some measure of confidence check without the need for expensive or exotic reference equipment. A PT100 RTD can be used as a water temperature check and the Emissivity of water is a known value.

Then there is the cheap and simple "Ambient temperature thermal reference" I previously detailed in this sub forum. With a decent PT100 RTD thermometer fitted, such would be a very useful test source. The Emissivity plate would beef to be tested though.

Fraser

[Bill W]

Some commercial sources have micro-machined surfaces, so creating an array of cavity black bodies which are then coated / painted.

The difficulty with even 2°C accuracy on a camera over temperature is how much this scales from the typical two point calibration at 20°C and 40°C black body and say in 10°C steps of camera temperature.  The accuracy at calibration has to be a lot better if you expect it to read 200°C +/-2°C with the camera at say 35°C (right between calibration points).

Cold accuracy is harder to get right, but mainly down to residual energy messing it up.

Bill

[Fraser]

Indeed Bill,
This is why I warned against the 'Voltnut" or "Timenut" mentality when it comes to thermal cameras and black body thermal sources. Thermography is a mine field of errors that could send a "Tempnut" crazy

What I had not previously realised was how variable the Emissivity of a paint can be over a pretty small temperature range. For me, it is important to have as flat a response as possible, rather than the highest possible emissivity at any particular temperature. Provided the thermal reference is of known Emissivity and temperature stability, it is good enough for most tasks.

The very best Black Body references seem to use the physics of the heated chamber/cavity to create a quality product without the need for very exotic coatings. As you say Bill, micro machined cavities seems a good way to achieve repeatable performance.

For those interested, I have several different Black Body thermal references of varying capability. I use them to carry out confidence checks on cameras when repairing or maintaining them. I have yet to have a camera that required true calibration.

I thought about posting a review of the Black Body references that I have but I realised that they are quite exotic and not easily found on the secondary market. It is therefore unlikely that fellow forum members will bump into them on eBay. A small hint to those wanting such a reference though....... think laterally.... these equipments are often not sold as Thermal Camera Black Body References... more obscure descriptions are common   Some of the units I have are actually intended for user confidence checking of equipment and are supplied by the OEM for that specific purpose. As it turns out, they are also perfect for thermal camera use The units are superbly made with precision thermal cavities and various temperature drive and stabilisation technologies. These range from integrated multiple heating elements to Peltier Modules driven by either simple temperature controlled 2 range analogue heater drive loops or complex TEC controllers. The units I purchased were worth the money paid just for the excellent thermal cavities they contained. I bought one the other day as part of a bulk purchase of medical equipment. The whole palette cost be £35 and I would have paid more than that for the Black Body thermal reference alone ! I have the bonus of some very nice medical electronics to sort through as well now

Fraser

[Fraser]

I will likely regret giving away my secrets but here are some current auctions that may interest those wanting a temperature reference......


https://www.ebay.co.uk/itm/Sherwood-Davis-Geck-First-Temp-Genius-Calibrator-3000-PC/162440799779?_trkparms=aid%3D111001%26algo%3DREC.SEED%26ao%3D1%26asc%3D20160908105057%26meid%3D14f5b6dcd0a743f7ad2d9cb363000dca%26pid%3D100675%26rk%3D1%26rkt%3D15%26sd%3D162440799779%26itm%3D162440799779&_trksid=p2481888.c100675.m4236&_trkparms=pageci%3Aec7442d9-5d02-11e8-95f7-74dbd180a1a4%7Cparentrq%3A8317fc421630abc2dbd6e095fff963d3%7Ciid%3A1


https://www.ebay.co.uk/itm/ALARIS-IVAC-9000-CORE-CALIBRATOR-Thermometer-Calibrator-W-O-ADAPTER-9035/301874060006?_trkparms=aid%3D111001%26algo%3DREC.SEED%26ao%3D1%26asc%3D20160908105057%26meid%3Dfcf9e1e5dc4144be900efbef522ca835%26pid%3D100675%26rk%3D3%26rkt%3D15%26sd%3D162440799779%26itm%3D301874060006&_trksid=p2481888.c100675.m4236&_trkparms=pageci%3A5323f339-5d03-11e8-a15e-74dbd180f925%7Cparentrq%3A831a9d281630aad71d55ee9cfff870a9%7Ciid%3A1

https://www.ebay.co.uk/itm/IVAC-9000-CORE-CALIBRATOR-Thermometer-Calibrator-W-O-ADAPTER-7630/291688478943?_trkparms=aid%3D111001%26algo%3DREC.SEED%26ao%3D1%26asc%3D20160908105057%26meid%3Dfcf9e1e5dc4144be900efbef522ca835%26pid%3D100675%26rk%3D2%26rkt%3D15%26sd%3D162440799779%26itm%3D291688478943&_trksid=p2481888.c100675.m4236&_trkparms=pageci%3A5323f339-5d03-11e8-a15e-74dbd180f925%7Cparentrq%3A831a9d281630aad71d55ee9cfff870a9%7Ciid%3A1


See what I mean about thinking laterally .  These units do not advertise themselves as thermal imaging Black Bodies or anything like that. They are IR Thermometer calibration check and calibration units. They have to be of decent quality to be licenced for medical use. Normally very expensive but their specialist use makes them cheap on eBay. I will not detail how to modify them for a particular need, but needless to say, they have a pair of very nice thermal reference cavities in them that are easily removed and compact. Some use a heating element whilst others use the very nice TEC Peltier module method of temperature creation and stabilisation. Both have a microprocessor controlling them but this can be bypassed if needed and replaced with a custom driver. As supplied, most of these units will automatically set themselves to produce a low and high temperature for the calibration check of in ear IR thermometers. From memory, the low cavity is around 34C and the high cavity is 40C but do not quote me on that. The fact that these units auto set the cavities at the required temperature ready for a calibration check is great as no hacking is needed to get the cavities running. Not all units are this friendly though so buy at your own risk!

Fraser

[Fraser]

A couple of grotty pictures taken with my iPad. This is a Genius unit that I am in the process of modifying.

Its modification is stalled due to other projects taking priority at the moment.

The Genius unit uses a heating element to control the temperature of the cavity. The IVAC calibrator uses a pair of Peltier modules. Of the two, I prefer the IVAC 9000 calibrator as it has potential for more versatile temperature coverage due to a Peltier based design being able to create below ambient temperatures. It can also use active positive and negative thermal drive to the radiation plate for fast temperature setting and stabilisation using dual polarity PWM An arduino would be perfect for the task and only an H Bridge driver would need to be added to the BoM.

Fraser

[Fraser]

On the LabIR paint front ..... no acknowledgement of my enquiry. Nil response so this company is not interested in a review of this product on the EEVBlog forum, even though I was offering to buy it at the advertised price, I.e. not asking for a free sample.

Dead End me thinks

Fraser

[Fraser]

Inside the IVAC 9000 calibrator. Just two screws and the cover slides off

This unit uses the TEC Peltier system to set and maintain the cavity temperature

These units are often sold without their power brick. They need 5V at 4A so nothing very special or hard to source.

Rubbish photos but you can clearly see the MAX133 ADC and those eight power transistors all lined up on one side look suspiciously like a pair of H Bridge drivers. One for each cavity. A custom reference would just need an arduino based temperature controller to be grafted into the unit As supplied, the unit just boots up and configures itself for a 'dumb' calibration check using the two cavities. It reports when they are at the correct temperature. Any other functionality it offers is bespoke to the calibration of the IR Thermometer and so of no interest to us.

Fraser

[Fraser]

One of the USA based IVAC 9000 units has now been sold. $25 for a pair of quality Peltier driven thermal cavities, a decent case and a PCB containing most of the parts needed for a custom thermal reference.... cheap, darn cheap 😄

I just searched for IVAC 9000 on eBay .... there is one in the USA for $10 and another for $20

Holy cow, if you are in the USA, you can pick these up for next to nothing !

Fraser

[Fraser]

Well three IVAC units sold on eBay USA today ... I wonder what caused that ? 😄

For anyone who buys one of these units, a hint regarding powering it.

There are two input pins that require +5V to be applied to them. One is the main 5V power input and the other is of unknown identity and purpose, but it needs +5V on it to boot the Calibrator. Maybe a PSU 'OK' line like on a PC power supply ?

The power connector is a standard 5pin 180 Degree DIN type. The socket is in the 'U' configuration or some would say it is inverter to that commonly found.

From left to right looking at the power socket ......

+5V / ? PSU OK ? / 0V / Chassis / 0V

Connect the '?' Pin to +5V to boot unit. The unit will draw less than 3A at start whilst it drives the two cavities to temperature. There is a separate chassis ground pin that is not connected to 0V on the controller PCB.

Once started the unit announces its revision and flashes "not ready". After the two cavities are at the correct temperature, the display will change to indicate that it is ready for tests. The instructions are helpfully printed on the top of the unit !

Fraser

[JohnG]

Well three IVAC units sold on eBay USA today ... I wonder what caused that ? 😄

Thank you!

John