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Subject:
From:
Wayne Thayer <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Wayne Thayer <[log in to unmask]>
Date:
Thu, 29 Aug 2013 18:04:54 +0000
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text/plain (290 lines)
That's different thinking!

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Rivera, Raye
Sent: Thursday, August 29, 2013 1:59 PM
To: [log in to unmask]
Subject: Re: [TN] Blowing Smoke

If this is an optical detector, why do you need actual smoke? Put a piece of tinted plexiglass in the detector as a calibration standard in the field. You can figure out what density of particles it is equivalent to in a lab with a particle counter.

Best regards,
Raye Rivera
 
 
QA Manager * Canoga Perkins * 818-678-3872  * [log in to unmask] -----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Wayne Thayer
Sent: Thursday, August 29, 2013 10:35 AM
To: [log in to unmask]
Subject: Re: [TN] Blowing Smoke

I think what I'm going to try next is two wirewound resistors glued together with some ceramic paste, or maybe just build a hammock between them with some aluminum foil.  Then try a drop or two of the liquid they use on model trains to simulate smoke.  If that doesn't get me anywhere, then maybe the heating element from an e-cigarette.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steven Creswick
Sent: Thursday, August 29, 2013 1:17 PM
To: [log in to unmask]
Subject: Re: [TN] Blowing Smoke

Wayne - agree.  That's why I pointed you to Gentex.  It's optical.  Used to be that all commercial aircraft had these detectors from Gentex

Steve C

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Wayne Thayer
Sent: Thursday, August 29, 2013 1:03 PM
To: [log in to unmask]
Subject: Re: [TN] Blowing Smoke

In an ionization-based detection system (technically illegal in my application because of the radioactive source required), you can check sensitivity by looking at the leakage current through the ionization chamber.  Most of these "in circuit test" systems simply put a resistor across the ionization chamber and measure the time it takes set off the alarm.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steven Creswick
Sent: Thursday, August 29, 2013 12:51 PM
To: [log in to unmask]
Subject: Re: [TN] Blowing Smoke

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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