Got an idea for a thermal imager mod to standard CCD security camera

[james_s]

It's certainly not something you'd want to carelessly play with, but there are far more dangerous things in most homes than a small flask of LN2.

[Chanc3]

I considered obtaining some Liquid Nitrogen to test my Agema 880 but my local suppliers require the use of an approved Dewar container which in the UK costs around £1000. The idea of transporting the stuff in a car does not appeal either.

On the safety front, i was advised that LN2 is safe in open environs but if a major spill occurred in my closed garage, I would likely expire before escaping    For these reasons I decided it was not worth the effort or risk for a museum piece.

Fraser

Fraser, some of my friends hire in LN for extreme overclocking events - you don't need to buy an approved container then. I'll see where he gets it from.

[Fraser]

Hi Chanc3,

That would be helpful. Thank you It would be nice to fire up the old gal and see if she still runs OK.

With regard to LN2 safety, I agree, it is not a dangerous substance if used sensibly. The dangers rear their ugly heads when an accident occurs, or someone does not understand what they are dealing with. Horror stories of people placing LN2 in sealed (unvented) flask containers thinking it will last longer.... then the inevitable explosion that follows

Fraser

[james_s]

Well there are always gonna be a few idiots out there. Several years ago there was somebody on this side of the pond who decided it would be a good idea to put the glass vessel from a Lava Lite on the stove (hob) and he was killed by the shrapnel. What possessed him to do such a thing I can only guess.

[-jeffB]

Hi Chanc3,

That would be helpful. Thank you It would be nice to fire up the old gal and see if she still runs OK.

With regard to LN2 safety, I agree, it is not a dangerous substance if used sensibly. The dangers rear their ugly heads when an accident occurs, or someone does not understand what they are dealing with. Horror stories of people placing LN2 in sealed (unvented) flask containers thinking it will last longer.... then the inevitable explosion that follows

Fraser
[/quote

Here's one:

http://blogs.sciencemag.org/pipeline/archives/2006/03/08/how_not_to_do_it_liquid_nitrogen_tanks

But I'll still take my chances with a LN2 tank outside my door in preference to a gas/petrol tank. You don't have to look nearly as far to find horror stories about those. You also don't have to do multiple hardware modifications to turn them into something that can explode.

In 7+ years with LN2 and liquid-helium dewars parked outside my office door, the worst mishap I ever encountered was an attack of dust-bunnies being gathered by scattering LN2 droplets from a spill.

[Fraser]

An interesting read......

https://web.archive.org/web/20010507134303/http://www.wpi.edu/News/Releases/19989/nitro.html

LN2 is sadly abused by some who should know better. Ever since I saw it freeze a flowers petals, I have had a healthy respect for it

As stated though, used correctly it is no more dangerous than handling flammable gases or fluids like petrol. In 1996 I watched with horror as a petrol attendant in the middle of Moscow filled my car with petrol whilst smoking a cigarette. Fortunately the fuel air mix must have been wrong as we both lived to fight another day. After that experience I was quite expecting to hear a loud BOOM! one day and see the mushroom cloud rising from this petrol station that was nearby. The petrol tanks were all above ground types too.

Fraser

[bap2703]

Are there any scanning type thermal imagers that do NOT require liquid nitrogen cooling?

Of course there are, basically any temperature sensor.
What creates the cooling requirement is the quantum detection for which the room temperature energy is of the same order than the infrared photon you are trying to detect.
Look for thermopiles or pyroelectric sensors.

[Fraser]

Scanning thermal imaging cameras have been around for a long time and so different detector technology was used over the years. The following are known to me.....

1. LN2 Cooled
2. Argon Gas Cooled using a Venturi and gas expansion
3. Sterling mechanical Cryo cooler
4. Peltier stack cooler

The most user friendly was the Peltier stack cooler as it required no consumables and was not mechanical in nature. The Peltier stack Cooled the detector to -70C and the detector material was Lead Selenide (PbSe)

The Agema 400 series,510 and  870 all used a PbSe Peltier Cooled detector with a scanning image creation system. The Agema 510 was a single axis scanner that contained a 128 pixel linear PbSe array for the vertical pixels. The scanning mirror swung in the horizontal place to create the sweep across the thermal scene.

Note that Peltier TEC's are also used in microbolometer sensors but for a completely different purpose...... to hold the sensor at +32C .... i.e. Not Cooled.

Fraser

[james_s]

So just to follow up, I checked with the Airgas branch that is a few blocks from my house, about 15 miles from Seattle. They do sell LN2, it's delivered from the truck that comes twice a week which may or may not have it on hand that particular time. Their suggestion is to leave your Dewar and they will contact you when it is ready to be picked up. The rep I talked to said no license is required required, you just need an account with them and a proper Dewar flask designed for the purpose. They didn't ask what I wanted the LN2 for and didn't seem to care. Getting an account is as simple as contacting them and providing the contact information they request.

[KE5FX]

So just to follow up, I checked with the Airgas branch that is a few blocks from my house, about 15 miles from Seattle. They do sell LN2, it's delivered from the truck that comes twice a week which may or may not have it on hand that particular time. Their suggestion is to leave your Dewar and they will contact you when it is ready to be picked up. The rep I talked to said no license is required required, you just need an account with them and a proper Dewar flask designed for the purpose. They didn't ask what I wanted the LN2 for and didn't seem to care. Getting an account is as simple as contacting them and providing the contact information they request.

Just get a metal Thermos and bring it to a welding-supply shop.  If they tell you to pound sand, just go to the next one.  Lather, rinse, repeat.  You shouldn't have to visit too many shops before you find one whose employees don't ask too many questions.

Source: this is what I did back in the 1990s to get rid of some warts.  Didn't have to visit any shops beyond the first one.