Wayne,
That is a good point about the smoke detectors, since there are two types -
the ionization types and the particulate types that work by scattering of
light.
Look at FAQ #3 at this site -
http://www.gentex.com/fire-protection/technical-support
It would appear that they have the calibration and degradation issues worked
out. I may still know some people there, but not sure how much help that
would be in this situation.
We used to ignite a ribbon of Mg to coat the inside of an integrating sphere
with white powder. If you can combust tiny performs of Mg, or nanofoil as
someone else suggested, that seems like it might satisfy your combustion
quantity issue - although may create another issue with transport and
handling....
Steve C
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Wayne Thayer
Sent: Thursday, August 29, 2013 12:33 PM
To: [log in to unmask]
Subject: Re: [TN] Blowing Smoke
Hi Dennis-
Yes, as you and Richard have pointed out, calibrating particle sensors is
not un-mapped territory. The systems are accurate and worthy of
withstanding the rigors of lawsuits.
But we can all see that there is a huge gulf between that kind of
calibration and the other end of the spectrum, such as seeing whether a
smoke detector is working OK.
Another point in that gulf is a counter designed to control a HEPA in a room
where a person has allergies. For that, they don't use a laser for
illuminating the particles, they just use an IR LED. Hence they don't know
if they are looking at one giant particle or a bunch of tiny ones. But they
actually appear to be useful anyway, and the cost for the sensor from
DigiKey is $12. Sharp tells you right up front on the data sheet that the
LED will fade over time, by as much as 50%, with a corresponding drop in
sensitivity. Also, the calibration curves provided in the data sheet show a
very wide range of "typical" calibration slopes.
So my gut tells me there should be some way of making a repeatable
experiment that could be used for comparing these cheap sensors to each
other and to watch the degradation in performance vs. time. I need to
vaporize a defined amount of material in a closed volume. Turns out to be
more challenging than I thought! It seems the diffusion of the vaporized
material is actually the easy part. Complete combustion of a defined amount
of material is hard.
Wayne
From: Dennis Fritz [mailto:[log in to unmask]]
Sent: Thursday, August 29, 2013 11:27 AM
To: Wayne Thayer
Subject: Re: [TN] Blowing Smoke
Good luck on this one, especially the "The idea is a cheap sensor" part.
Particle measurment in either air or liquid is pretty well developed. IEST
is the standards organization and there are also IEC international
regulations/certifications
I googled "air particle counter calibration" and a lot of stuff came up -
most all probably too complicated for what you need - "cheap". However,
this link gives some background on your problem and a bit of "who certifies
what".
http://www.particle.com/wp-content/uploads/downloads/2012/02/WP-MET-ONE-ISO-
21501-Calibration-of-APC-from-Metrology-Perspective-US.pdf
Good luck.
-----Original Message-----
From: Wayne Thayer <[log in to unmask]<mailto:[log in to unmask]>>
To: TechNet <[log in to unmask]<mailto:[log in to unmask]>>
Sent: Thu, Aug 29, 2013 10:06 am
Subject: Re: [TN] Blowing Smoke
To answer previous question:
The idea is a cheap sensor. 3rd world homes are notoriously smoky due to
the
cooking fire and due to kerosene lamps. Most of the smoke is carbon. There
are
lots of ideas for improving these homes (like LED lights with solar
rechargers)
so we can "improve their lot" by making it more healthy for kids to study
inside
(or maybe so they can buy stuff on the internet?). Anyway, the aid groups
want
a way to see what the bang for buck is in improving the indoor environment,
so
they need a sensor. These sensors work by shining an LED or laser through
an
air stream, and measuring the amount of light which is reflected off-axis by
the
particulates in the air.
How does the bicycle pump (actually I'm imagining a disposable plastic
syringe)
pick up a defined amount of cigarette smoke? Maybe arrange a fixture which
leaves the cigarette burning and allows the smoke to just rise into the open
end
of the syringe for a set amount of time, then put the plunger in. Might
work-cheap to try!
As to the other suggestions, such as the nichrome wire, I keep coming back
to
needing some kind of heated basket so I can make sure I burn 100% of
whatever I
put in there. A circulating fan and Brownian motion should make the
environment
pretty uniform, although with the tests I've been doing, I get a spike with
an
exponential decay as the particles settle. Still, the interior of the 5
gallon
bucket appears pretty uniform, even though the peak duration is only about
40
secs.
Wayne
From: Inge Hernefjord
[mailto:[log in to unmask]<mailto:[log in to unmask]>]
Sent: Thursday, August 29, 2013 4:45 AM
To: TechNet E-Mail Forum; Wayne Thayer
Subject: Re: [TN] Blowing Smoke
Don't laugh now, I am serious. A kind of cycle pump, but with a very small
diameter nozzle. Pull the handle and suck a second sniff of cigarett smoke,
continue pulling handle until pump is filled with air/smoke mixture. Now
press
handle slowly and you get a constant stream of mixture. Simple and cheap.
Guess
the nozzle should be fractions of a millimeter.
Inge
On 28 August 2013 08:07, Wayne Thayer
<[log in to unmask]<mailto:[log in to unmask]><mailto:[log in to unmask]
om<mailto:[log in to unmask]>>>
wrote:
OK, here's another problem I've been playing with (although it has little to
do
with IPC mission, it might be related).
I am trying to build a system for measuring airborne particulates for
humanitarian organizations looking for inexpensive ways to measure/monitor
indoor air quality. There are cheap sensors available which might do the
job,
but they would need periodic re-calibration.
So I need a controlled, extremely small amount of smoke. At first, I
thought
this would be trivial: Find a cheap part at DigiKey and put too many watts
through it. Way too much smoke and too little control. Then I tried
burning
thin wires. Too irregular because sometimes they incinerate completely and
other times they find a tiny defect and just burn that until the wire stops
conducting. Then I tried just heating the wire enough to burn off the
insulation. Still too irregular! I did just a few experiments and got 30%
variation.
Now I'm starting to think maybe a tiny piece of paper on an automotive
cigarette
lighter. That's a lot of power to get that glowing, and it is not
convenient to
attach to. Any other ideas?
Wayne
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