ping Phil Hobbs

[Chris Jones]

Hi Phil,

You might find this interesting:

Design of a low-cost, open source, condensation particle
counter("OpenCPC") - EAC 2023

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...

[Phil Hobbs]

Post by Chris Jones
Hi Phil,
Design of a low-cost, open source, condensation particle
counter("OpenCPC") - EAC 2023
http://youtu.be/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

[Chris Jones]

Post by Phil Hobbs

Post by Chris Jones
Hi Phil,
Design of a low-cost, open source, condensation particle
counter("OpenCPC") - EAC 2023
http://youtu.be/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

Their design is a bit unusual in that they do not illuminate the whole
stream of particles, the laser beam is smaller, and this means that they
miss some particles and the fraction that they miss is size-dependent.

I think they are using isopropanol, I guess because it is more widely
available.

I'm pleasantly surprised that they are getting a huge signal compared to
the background and noise.

I'm waiting (and pestering them gently) until they upload their design
files, as it's meant to be open-source.

[Phil Hobbs]

Post by Chris Jones

Post by Phil Hobbs

Post by Chris Jones
Hi Phil,
Design of a low-cost, open source, condensation particle
counter("OpenCPC") - EAC 2023
http://youtu.be/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

Their design is a bit unusual in that they do not illuminate the whole
stream of particles, the laser beam is smaller, and this means that they
miss some particles and the fraction that they miss is size-dependent.

All laser particle counters are like that. For a given particle size,
operating in the shot noise limit, you can interrogate a fixed volume per
joule of laser energy.

You can apportion that as a big beam and slow motion, or a smaller beam and
higher air speed, but you get the same volumetric rate until you find
yourself limited by some other noise source. Johnson, amplifier, and 1/f
are the usual culprits.

Cheers

Phil Hobbs

Post by Chris Jones
I think they are using isopropanol, I guess because it is more widely
available.

Dunno how well that would work.

Post by Chris Jones
I'm pleasantly surprised that they are getting a huge signal compared to
the background and noise.

CNCs turn everything into 1-2 micron boulders, which is the point of the
exercise.

Post by Chris Jones
I'm waiting (and pestering them gently) until they upload their design
files, as it's meant to be open-source.