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From: Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net>
Newsgroups: sci.electronics.design
Subject: Re: ping Phil Hobbs
Date: Fri, 15 Mar 2024 19:09:55 -0000 (UTC)
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Chris Jones <lugnut808@spam.yahoo.com> wrote:
> Hi Phil,
> 
> You might find this interesting:
> 
> Design of a low-cost, open source, condensation particle 
> counter("OpenCPC") - EAC 2023
> 
> https://www.youtube.com/watch?v=1mmV81vFGys
> 
> Any ideas on ways to make it easier to build, or to count a higher 
> fraction of the incoming particles?
> 
> The end application is fit-testing of respirators, similar to the TSI 
> Portacount but cheaper.
> 
> BTW I already recommended your book to them, and pointed out that you do 
> consulting...
> 
> 
> 

Condensation nucleus counters are old friends from my crud detection days
30 years back. 

They work by pulling air through a saturated vapor of n-butanol and then
into a regular dark field particle counter. That’s why the sample volume is
smaller—you have to limit the alcohol consumption. 

The cool thing about them is that the particle radius grows linearly with
time, up to a micron or so. The rate of collection per area is constant
until the growing droplet starts depleting the local concentration of
butanol. 

That lets you detect particles down to 10 nm or so, but obliterates any
size information. 

Cheers 

Phil Hobbs 

-- 
Dr Philip C D Hobbs  Principal Consultant  ElectroOptical Innovations LLC /
Hobbs ElectroOptics  Optics, Electro-optics, Photonics, Analog Electronics