how do I measure CO

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Hello all

Once again I humbly seek your assistance :-)

I would like to build a CO meter for when I do the service
on my car. How does one measure carbon monoxide ?

I've searched google until I exhausted every possible
combination of keywords (+CO +Meter, +CO, +resistor, "measuring
CO", "measuring carbin monoxide", etc).

Anyone knows where I can find the relevant information ? what I would
like is a simple component that will change resistance when the
CO in the air around it changes. I dont need a linear change either,
although one that has a linear change would be easier to code for.

thanks in advance

goose,

Re: how do I measure CO

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I thought the CO meters measured thermal conductivity of the exhaust gas.  I
guess they use a hot wire with a known throughput of gas to cool the wire.
The amount of cooling giving an indication of the CO level.



Re: how do I measure CO

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CO can be measured with an optical system.
There are CO absorbing wavelengths. A thermopile
with such a filter does it.

perkin-elmer selles the sensors

Rene
--
Ing.Büro R.Tschaggelar http://www.ibrtses.com
Your newsgroups @  http://www.talkto.net

Re: how do I measure CO
goose threw some tea leaves on the floor

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CO percentage in parts per million is usually measured by pumping air
containing CO after it has been filtered and cooled, thru a tube.

Each end of the tube contains quartz windows and one end has a filament
or heater glowing dim red which provides the light source.

The other end has a chopper wheel which interrupts the light from
reaching a thermopile sensor.

Such instruments are very accurate but require regular calibration
using *expensive* calibration gas that has been analysed in a lab.

Such equipment usually costs around several thousand dollars
Australian and also measures CO2, and oxygen percentages.

A modern car will only output perhaps 10 ppm CO, while a old car from
the 80's may output 700PPM or more.

A cheap alternative may be a sensor built by "Figaro" but it won't be
anywhere near as accurate.

--
              Kind Regards from Terry
    My Desktop is powered by GNU/LinuX, Gentoo-1.4_rc2  
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Re: how do I measure CO
What about starting with the guts out of a common $35 household CO
alarm?
------------------------------------------------------------------------
  Paul Kasley, Beams Division / Controls Hardware
  Fermi National Accelerator Lab, PO Box 500, MS 360
  Batavia, IL 60510



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would
filament



Re: how do I measure CO

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[snip]

Or get a ready made vehicle exhaust measuring system for £135 from
http://www.gunson.co.uk and save yourself a lot of time and effort.

Peter



Re: how do I measure CO
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Ruby/Mica in some analysers.
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Sounds like an old Andros 600 analogue bench you're describing here!
Used in Sun DGA1800 analysers IIRC. Old tech, take a look at the Andros
Microbench, LED source and <30s warm-up time. Fits in the palm of your
hand (excluding pneumatics)
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Once every 30 days by the user and once a year by a UKAS accredited
engineer for most equipment or never by the user and UKAS every six
months to meet the requirements of the emissions test in the UK, the
user cal gas is good for many hundreds of calibrations though and costs
around a hundred UKP, the UKAS cal gas (probably from the same batch as
the user gas) costs around twice that but is good for maybe a thousand
calibrations due to the bottle size. Both are certified for only two
years but will keep for many years if traceability isn't important
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Can be had second hand for under 300 UKP for a four gas analyser (CO,
CO2, HC and O2, calculated Lambda)
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10 PPM is quite high, if the machines are to be believed a good, hot
engine and Cat is under 5PPM IIRC.
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If the car is a non cat or an open loop management system then the CO
measurement needn't be that accurate, a simple glass tube with the
appropriate mechanical gas filtering can be used with an IR sensor and
IR led to give a relative indication, it can even be fairly accurate if
calibrated and temperature compensated.
--
Clint

Re: how do I measure CO
Clint Sharp threw some tea leaves on the floor

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So right!

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Yes, I did a lot of work on the Andros benches! Also the old Ausie Repco
units.

The Andros was my favourite, so easy to cal and so accurate.


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Here is a man who knows gas analysers folks!

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Plus there is some real junk about, especially benches made out of pvc,
with nasty little vacuum pumps.

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So true, I was being generous :)

I remember the company mechanic once informing me that their unit was faulty
as a new Toyota (can't remember the model) wouldn't diplay any CO. Sure
enough the gas analyser seemed to be totally dead CO wise. Our spare
unit was the same, that car had so little CO we couldn't read it!

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Really? I haven't seen a solid state model, but then again I haven't
worked in that area for a few years.

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Thanks for the update Clint:)


--
              Kind Regards from Terry
    My Desktop is powered by GNU/LinuX, Gentoo-1.4_rc2  
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Re: how do I measure CO


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This is one way:

http://www.epa.qld.gov.au/environmental_management/air/air_quality_monitoring/air_pollutants/carbon_monoxide /

It took me a few seconds to find it with Google.

Leon


Re: how do I measure CO

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http://www.veris.com/products/env/gas/cde.html sells one in the
0-2000 ppm range, but it's +/- 20 ppm - good enough for finding
the minimum as you adjust things on the engine, but not good
enough to tell you whether you will pass the smog check.


--
Guy Macon, Electronics Engineer & Project Manager.  Remember Doc Brown
from the 'Back to the Future' movies?  Do you have an "impossible"
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Re: how do I measure CO

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I thought there was a related project in Popular Electronics
years ago. The sensor was a heated pellet of tin oxide.
Supposedly, it could detect any oxygen-reducing gas; not just CO.

I don't know if these sensors are still the best way to go...?


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