Nikken 1394 particle counter AQM particle size spec?

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We have a lot of wildfires in Oregon and the
TV is warning of seriously bad air quality
due to smoke.

OK, so I took the Nikken 1394 outside.
It registers 2000 particles/liter.
The scale is yellow indicating no big deal.

HMMM....

I dug out the Dylos DC1100 Pro Calibrated to
a particle size split at 2.5 microns.

It read 5322 total count particles per .01 cubic foot.
96% categorized as below 2.5 micron.
The scale on the chart is in the range
"kiss your sweet ass goodbye", which is in line with
the air quality warnings.

After accounting for the units difference, there's
an order of magnitude difference between the readings.

If I take both devices over to the sofa and bang on
the cushions, I can drive both off scale.

Symptoms suggest that the problem is relative to particle
size.

The Nikken (what passes for a manual) gives no
clue as to particle size.
The Nikken website has no info.
This is all I found on the web

http://802.11junk.com/jeffl/Nikken%201394%20Air%20Quality%20Monitor/

I'd rather not take it apart if it's working as designed.
Anybody got any relevant info?

Re: Nikken 1394 particle counter AQM particle size spec?

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I've done some aerosol particle counters down to nm-level. Th Nikken
unit looks like it has simple LED-based optics and maybe
electrometer-based measurement, which typically measures total 'mass' of
particle down to nm-range. There's not a lot of mass in small particles,
so electometers are typically used with size selectors when measuring
nm-size particles.

Dylos has two detectors, one with a cut-off of 2.5um and other with
500nm. Cut-off is the diameter where 50% of the particles are counted.

Nikken has a cut-off probably in the 1-5um range. And it might not be
counting particles, but rather using 'photometric mode', where the total
intensity is used to estimate particle count. This is used also in
scientific particle counters when going over the capability of counting
single particles.

The count of smaller than 2.5um particles can be really high on forest
fires. I always remember when we got our condensation particle counter
prototype working in the lab, it indicated 5M particles/l. We thought
it was an error, but we had just reached way better cut-off of 7nm than
we thought and there was a big forest fire about 300km away!

The difference (2000 vs 19000/l) you're seeing is well explained by
different cut-offs.

--
mikko



Re: Nikken 1394 particle counter AQM particle size spec?
On 8/16/2018 12:25 AM, Mikko OH2HVJ wrote:
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That was my conclusion, but...If I understand correctly,
the Nikken measures reflections from particles.
The amplitude of the light reflection should be proportional
to the square of particle size.  You could sort particle size
by reflection amplitude.

Dust on the optics could reduce the reflection amplitude and
make huge difference in measured amplitude.  The detection threshold
would move up to larger particle size.

If the cutoff is correct as designed, there's nothing to be done.
If it's changed because of optical contamination, taking it apart
to clean the optics might be useful.
I have no idea of the history of the device.  It may have been
used in an environment that led to dust coating the optics.

For a device where you can't filter the input, wouldn't you
expect optical contamination?  Maybe it calibrates itself before
it starts the fan???

I've been using the Nikken as a survey tool.
In its current condition, it appears to be useless in finding
contaminants that are dangerous to health.
It does appear to be sensitive to household dust like you get
when you pound on the sofa cushions.

If the Dylos will run on 8V, I think I'll make a battry pack
for it.

___________________________________________________________

The Dylos has a real-time bar graph.  It sits mostly at the
zero end of the scale, then flashes periodically to full scale.
There's a long averaging time in the numerical readout.
That suggests an infrequent hit in a small volume averaged
and scaled up by a huge amount.

It's been years, but I thought I'd read that the Dylos does
the same dark-field reflection method and differentiates
particle size by amplitude of the signal.

I have slightly better knowledge of the Dylos's history.
Bought it from someone who'd bought it new and used it in
controlled 'inside' conditions.
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Re: Nikken 1394 particle counter AQM particle size spec?
On Thursday, August 16, 2018 at 4:35:03 PM UTC-4, mike wrote:
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I think most of your post is correct. However, I'm not sure how the Dylos compares to the definition for PM2.5 and PM10.

If I understand correctly, the Dylos Pro counts particles equal or greater than 2.5 microns and 10 microns. But the PM2.5 and PM10 spec is equal to or less than 2.5 microns and 10 microns. Just the opposite.

Eventaully, the Dylos will require cleaning. Here are two articles that discuss it.

Cleaning a Dylos  
https://ruaraidhd.bitbucket.io/SOP%20cleaning%20a%20Dylos.pdf
  
Dylos Air Particule Conter experiment maintenance
http://aqicn.org/faq/2013-10-21/dylos-air-particule-conter-experiment-maintenance/


Re: Nikken 1394 particle counter AQM particle size spec?
On Thursday, August 16, 2018 at 5:57:13 PM UTC-4, Steve Wilson wrote:

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Boy, I really screwed that up. I even posted the Dylos manual section above.

The Dylos User Manual states:

The DC1100 displays the concentration of particles in the air. As
stated in the overview section, the numbers represent particles in
.01 cubic foot of air. Thus, if the unit displays 676 on the left
and 17 on the right there are approximately 67,600 particles 1
micron or greater per cubic foot of air and, likewise, 1700
particles greater than 5 microns per cubic foot of air. (Note: if
you purchased the "Pro" model then your small particle threshold is
0.5 microns and your large particle threshold is 2.5 microns.)  
  
So the Dylos Pro displays particles between 0.5 microns and 2.5 microns. Everything below is cut off.

There is no PM10 measurement. It simply shows everything above 2.5 microns.

And it does require maintenanc as shown below.

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Re: Nikken 1394 particle counter AQM particle size spec?

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Sometimes yes, sometimes no. The reflectance can be different (think
of soot and water droplet). For small particles you start getting interesting
interference patterns. The refractive index of liqud droplets differ.
For larger particle concentrations you get multiple particles in the
beam at the same time (coincidence).

Google for aerosol particle sizer for more info.  

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You can arrange the airflow so that it keeps most of the stuff away
from optics, but keeping everything out is almost impossible without
additional filtered flows.

--
mikko

Re: Nikken 1394 particle counter AQM particle size spec?
On Wednesday, August 15, 2018 at 9:11:47 PM UTC-4, mike wrote:
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I have two Dylos Pro counters. They compare favorably side-by-side. See

https://imgur.com/a/SzhfCpR

I have been monitoring the partcle count in monitor mode since 2009. I can  
find no rhyme or reason for the changes in the particle count, except after
 taking a shower. Water particles flood the apartment and drive the reading
s sky-high.

The hourly count can vary from 100 to over 10,000 when I wake up. This mean
s the air has been still for hours and there is nothing to explain what mig
ht be causing the changes.

The Dylos User Manual states:

The DC1100 displays the concentration of particles in the air. As
stated in the overview section, the numbers represent particles in
.01 cubic foot of air. Thus, if the unit displays 676 on the left
and 17 on the right there are approximately 67,600 particles 1
micron or greater per cubic foot of air and, likewise, 1700
particles greater than 5 microns per cubic foot of air. (Note: if
you purchased the "Pro" model then your small particle threshold is
0.5 microns and your large particle threshold is 2.5 microns.)

The current count is 2317/40. I cannot visualize a distribution where the c
ount varies by a factor of 57 for a factor of five change in size. That is  
a very steep function.

You cannot use the size chart for the Pro version. It says somewhere in the
 User Manual that it doesn't apply for the Pro version.

I think the Pro model is simply too sensitive, just like a scope with the g
ain set too high. I disregard the 0.5 micron readings.

I think the companies that sell particle counters are making a fortune sell
ing units that really don't tell you much about the air quality or what is  
in the air that can harm you. The counts make no distinction betweem harmle
ss particles, such as water particles, and harmful particles such as soot.

I should mention that I have a fan in the window gently blowing air in from
 outside. I live fairly close to a road, so there may be some dust blown up
 by road traffic during rush hours. But I live in a small  town, so rush ho
ur isn't much. Also, I turn off the fan and close the window from time to t
ime, and still get similar fluctuations in readings. So without some way to
 identify the particles and separate the harmful ones, the readings don't m
ean much.


Re: Nikken 1394 particle counter AQM particle size spec?
I forgot to mention, I also have a Nikken 1394. I could find no correlation between it and the Dylos, so I put it on the shelf.

Basically, both counters are useless.

Re: Nikken 1394 particle counter AQM particle size spec?

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Should be quite easy. Think of the particle volume instead of
diameter. 5x diameter means 125x volume and mass.

Air quality limits are often expressed as PM2.5/10PM, i.e. particle
_mass_ of 2.5 and 10um particles.

These together mean that same particle mass has huge difference in
count.

Regarding dangers of particles - smaller particles get deeper into your
lungs and have bigger area/mass ratio.

--
mikko


Re: Nikken 1394 particle counter AQM particle size spec?
On Thursday, August 16, 2018 at 8:52:33 AM UTC-4, Mikko OH2HVJ wrote:
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The Dylos measures the particle size, not the volume. Since you do not know the density of the particle, you cannot infer the mass.
  
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Re: Nikken 1394 particle counter AQM particle size spec?
On 8/16/2018 7:03 AM, Steve Wilson wrote:
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That's one of the issues.  The published AQM numbers in the news are  
mass/air volume.  Particle counters give count/volume.  You'd need to  
convert
between the two to get comparable readings.
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Re: Nikken 1394 particle counter AQM particle size spec?

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That's why I used 'mass' previously in the article. The linear size/volume
relation is valid for same density material only. Also, the charging
efficiency of the particle entering an electrometer differs.

Real particle mass measurement is done in a different way, but the air
quality numbers usually are based on approximations done from other
methods.

--
mikko

Re: Nikken 1394 particle counter AQM particle size spec?

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Oh-oh.  I've been discovered by Google.

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You're no fun.  Learn by destroying which means tear it apart until
you understand how it works.

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Page 4 of the manual proclaims:
   Level   Color   Particles/liter
                   of air
     1     blue      500
     2     yellow   1000
     3     yellow   2000
     4     yellow   3000
     5     red      5000
     6     red      5000+

<https://en.wikipedia.org/wiki/Nephelometer
Link to a previous discusion about a light scattering nephelometer:
<https://groups.google.com/d/msg/sci.electronics.design/CKc57kEaijA/yZR8lgIa5soJ
See:
<https://groups.google.com/d/msg/sci.electronics.design/CKc57kEaijA/xdV8p7aBM3MJ
for a list of links to various similar devices by Sharp and Sinyei
along with explanations as to how they operate.

The sensor has a big CAM-003 inscribed on its case, but no manufactory
and hints as to who made it.  I can't find anything useful with
Google.  General image search for nephelometer:
<https://www.google.com/search?tbm=isch&q=nephelometer
which finds some interesting stuff.

"Sizes of airborne particles as dust, pollen bacteria, virus..."
<https://www.engineeringtoolbox.com/particle-sizes-d_934.html
    Burning Wood  0.2 - 3.0 microns

25 dust sensors on Digikey:
<https://www.digikey.com/products/en/sensors-transducers/dust-sensors/509>
    
"Wildland fire ash: Production, composition and eco-hydro-geomorphic
effects"
<http://cesonoma.ucanr.edu/files/272305.pdf



--  
Jeff Liebermann     snipped-for-privacy@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
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Re: Nikken 1394 particle counter AQM particle size spec?
On 8/16/2018 3:44 PM, Jeff Liebermann wrote:
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Based on your experience, I think I know how it works.
The question is not how, but what is this particular model
Nikken 1394   actually measuring
in terms of particle dimensions.
My symptoms suggest that it does a poor job on forest fire smoke
from 200 miles away.
Is your experience different?
Is mine broke?
Or just not suited for very small particles?
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Thanks for the links.  I'm sure that's all good stuff, but does it
answer the question, "what can I expect from the Nikken?"
Should I take it apart in anticipation that cleaning it will help
measure small particles?  If I can't, I should just not try to use
it for that.
The Dylos seems to read closer to what the Air Quality websites
publish.  I built  a battery pack for it, so now it's portable.

Re: Nikken 1394 particle counter AQM particle size spec?
On 08/17/2018 02:10 AM, mike wrote:
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Almost all decent particle counters measure scattering cross-section in  
a darkfield geometry (air flow along X, laser along Y, detector and  
collection mirror at +-Z).  Some use a polarizer on the detector to  
reject the CW scattered light (and its attendant shot noise), but that's  
usually only an issue with PMT detection, whereas most use straight  
photodiodes.  It usually isn't worth working that hard, because in an  
incoherent light scattering system the detected signal goes as the sixth  
power of the particle radius, so a factor of 10 sensitivity improvement  
takes you from 0.2 um to 0.14 um, say.  (This is in the Rayleigh limit,  
of course.)

The measured signal depends on position in the beam, composition,  
density and shape as well as size, so the size readout is calibrated  
using polystyrene latex (PSL) spheres, sometimes with a histogram  
correction to account for the effects of impact parameter (i.e. the  
nearest distance from the beam axis).

Crappy ones just look for average extinction using a LED, just like a  
smoke detectors.

Cheers

Phil Hobbs

--  
Dr Philip C D Hobbs
Principal Consultant
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Re: Nikken 1394 particle counter AQM particle size spec?

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I know how it is suppose to work.  That's in the literature for the
various sensors found in the mess of links I provided.  What I don't
know is what this particular device can do.  It is not a scientific
instrument, show no sign of calibration or testing, and seems to be
made for the paranoia market.

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Phil Hobbs explained most of that.  However, it looks like all you
want is a number.  I don't have specs on the specific model light
scattering box inside the unit, but I think this one is close:
<https://www.digikey.com/product-detail/en/sharp-socle-technology/GP2Y1010AU0F/1855-1012-ND/720164>
<https://media.digikey.com/pdf/Data%20Sheets/Sharp%20PDFs/GP2Y1010AU0F.pdf>
The data sheet does not specify the range of detectable particle
sized, but does mumble:
   GP2Y1010AU0F is a dust sensor by optical sensing system.  
   An infrared emitting diode (IRED) and an phototransistor  
   are diagonally arranged into this device.
   It detects the reflected light of dust in air.
   Especially, it is effective to detect very fine particle  
   like the cigarette smoke.  
   In addition it can distinguish smoke from house dust  
   by pulse pattern of output voltage.

Ok, so it can detect cigarette smoke and house dust.  Digging through
a handy table of dust particle sizes at:
<https://www.engineeringtoolbox.com/particle-sizes-d_934.html
I find:              microns
   Burning Wood     0.2 - 3.0
   Fly Ash            1 - 1000
   Combustion      0.01 - 0.1    
   Household dust  0.05 - 100
   Smoke from Natural Materials  0.01 - 0.1
Nothing found for cancer sticks (cigarettes).

House dust and fly ash have too wide a range of particle sizes to be
useful.  That leaves burning wood, combustion products, and smoke from
natural materials as useful ranges.  Therefore, I would guess(tm) that
the Nikken can detect particles from 0.01 to something less than 3.0
microns.  That fits nicely with most of the smoke produced by the
fires.  Normally, I would verify this by simply hanging a sheet of
sticky paper out the window for a while to collect the local dust and
ash.  Then, a microscope and reticule to determine the particle size
from the fires.  Fortunately, the EPA has saved me the effort:
<https://www3.epa.gov/ttnamti1/files/ambient/smoke/wildgd.pdf
   Particulate matter in wood smoke has a size range near  
   the wavelength of visible light (0.4 - 0.7 micrometers)
That's well within my guess(tm) as to the detection range of the
instrument, so it should detect smoke from the fire.

There's quite a bit of information in the above EPA document on what
constitutes harmful concentrations of smoke.  Methinks that's what you
should be interested in calculating, not the number or size of the
particles.  The document probably explains it better than I can.

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Most areas have air quality monitoring stations with associated web
pages.  This is the one for my area:
<http://air.mbuapcd.org
<https://sites.google.com/firenet.gov/wfaqrp-airfire-tools/
You should be able to find the approximate smoke concentration on such
a site.  

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I don't know.  We had a few bad days were there was quite a bit of
haze from the fires.  However, I didn't bother checking the
concentration with the Nikken for that fire, or any previous fires.

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I don't think so.  It responded normally (2000 particles/liter) when
you went outside.   You might want to try my favorite test.  Find a
cloth sofa or padded seat.  Fire up the Nikken meter.  It should read
low on the graph.  Now, beat on the sofa cushions once or twice.  The
meter should indicate full scale.  It's quite sensitive to house dust.

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No.  The particle sizes calculated by Phil Hobbs is the minimum
particle size.  There is no maximum expect perhaps limited by the
input air filter.  I think it's the box to the right of the fan:
<
http://802.11junk.com/jeffl/Nikken%201394%20Air%20Quality%20Monitor/Nikken-AQM-03.jpg

held in with one obvious screw (but I'm not sure).  Blow with clean
and dry compressed air.  If there's a big pile of dust inside, the IR
sensor box is probably also full of dust.  

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I can't answer that directly.  What I've tried to do is use data from
a similar IR dust sensor to deduce what the Nikken might do.  Without
data on the sensor used, I can't do much.  I was hoping that you would
dig through the mess of links and do your own research.  I can only do
so much.

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Unless you're prepared to go through some kind of calibration
procedure, the best I can suggest is to have me run some kind of
detection test and compare results on your unit.  I could set fire to
various common objects and hope that the type and quantity of smoke
produces is identical.

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Well, if you have two units, and one of them is suspect, take the
suspect unit apart as I previously suggested.  

Good luck.

--  
Jeff Liebermann     snipped-for-privacy@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
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Re: Nikken 1394 particle counter AQM particle size spec?
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Boulders are easy, but getting down much below 0.1 um isn't. Ambient air is
 very roughly 10,000 times dirtier than clean room air, so you can trade of
f a lot of sampling volume to see smaller particles, but that a**6 dependen
ce is a pretty heartbreaking thing to fight.  

In ambient detectors the upper size cutoff has a lot more to do with popula
tion density than sensitivity.  

Cheers

Phil Hobbs

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