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.
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
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
I'd rather not take it apart if it's working as designed.
Anybody got any relevant info?
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
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
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
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
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.
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.
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.
You're no fun. Learn by destroying which means tear it apart until
you understand how it works.
Page 4 of the manual proclaims:
Level Color Particles/liter
1 blue 500
2 yellow 1000
3 yellow 2000
4 yellow 3000
5 red 5000
6 red 5000+
Link to a previous discusion about a light scattering nephelometer:
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:
which finds some interesting stuff.
"Sizes of airborne particles as dust, pollen bacteria, virus..."
Burning Wood 0.2 - 3.0 microns
25 dust sensors on Digikey:
"Wildland fire ash: Production, composition and eco-hydro-geomorphic
Jeff Liebermann firstname.lastname@example.org
150 Felker St #D http://www.LearnByDestroying.com
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?
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.
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,
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
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.
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:
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:
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:
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.
Most areas have air quality monitoring stations with associated web
pages. This is the one for my area:
You should be able to find the approximate smoke concentration on such
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.
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.
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:
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.
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
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.
Well, if you have two units, and one of them is suspect, take the
suspect unit apart as I previously suggested.
Jeff Liebermann email@example.com
150 Felker St #D http://www.LearnByDestroying.com
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