Path: ...!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail From: Phil Hobbs Newsgroups: sci.electronics.design Subject: Re: ping Phil Hobbs Date: Fri, 15 Mar 2024 19:09:55 -0000 (UTC) Organization: A noiseless patient Spider Lines: 44 Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Injection-Date: Fri, 15 Mar 2024 19:09:55 -0000 (UTC) Injection-Info: dont-email.me; posting-host="54c9ee1f83501721a2fbc4a05108f919"; logging-data="2559893"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX1/1bCpUJ9O50cM8nOk07k5f" User-Agent: NewsTap/5.5 (iPhone/iPod Touch) Cancel-Lock: sha1:IvXgKRcK1AQCdUZpqgjiIS6mu5w= sha1:91yckHvlUP71c1xPBMXiU92X21k= Bytes: 2355 Chris Jones 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