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Re: Portable CO meter
Phil Payne wrote:
> In message <email@example.com> Tony Lum
> > Phil, this may be rather extreme and requires modification of your
> > system. I read a article in EC mag about how Techtonics Tuning
> designed a
> > fuel enrichment device triggered by the WOT and temp sensor. They
> > able to measure fuel mixture by way of a "high" speed OXY sensor. I
> > realize that your engine doesn't have one, but have you considered
> > one? I read its quite easy to obtain the fitment, cut a hole in
> > exhaust pipe, weld in the mount, and screw in the sensor. You can
> use the
> > 3 wire kind to make sure it warms up fast. Now with this sensor in
> > you can hook up all types of instrumentation. How about a laptop
> with a
> > A-D coverter pcmcard and chart the output voltage vrs rpm etc, etc.
> Thought about that.
> As it happens, I have a redundant (but reliable and well-built) AST
> Premium PowerExec 386SX25 laptop with two PCMCIA slots.
> I've looked at a number of packages. Farnell do an attractive one -
> an 11-channel A/D converter that plugs into the parallel port and
> uses cheap, nasty and probably very efficient DOS software.
> Experimentation is suspended while I get the car through its annual
> inspection. It needs a new centre exhaust section, so I'm putting in
> a piece of cheap crap (rather than the real Audi part) so I can do
> some cutting and banging after the inspection is passed without
> damaging anything expensive. But one reason for the 'portability'
> requirement is that I want to make measurements on a reasonable sample
> of cars - not just my own.
> Phil Payne
> Phone: +44 385302803 Fax: +44 1536723021
About 1 year ago, I bought a $250 (USD) CO meter, that was
manufactured in the UK and sold under the brand name "GasTester." It
has proven to be almost completely useless. It is based upon a cheap
tin oxide sensor that with proper firmware would be reasonably
responsive and *somewhat* accurate in measuring CO concentrations on the
order of about 100 to several thousand ppm, (about .0001 to .005
percent) These sensors are used in household CO meters/alarm, (with
which I've done some reverse engineering work.) Unfortunately, we're
talking about measuring far greater concentrations of CO-- a task these
cheap ($10) sensors just weren't designed to do, and simply can not do
well. Even after proper warmup and "calibration", the measurement on my
meter fluctuates WILDLY. I don't care if you had a CRAY III in your
back seat-- "you can't shine shit." The CO concentration data you'll
get out of anything but a good quality infra-red gas analyzer ($750
minimum,) will be useless. If you intend to service more than a few
Bosch fuel injected vehicles, the $750 price tag is well worth it-- I'm
still saving for one myself. If you do discover a GOOD CO meter for a
reasonable price, that is not based upon a tin oxide sensor, I'd love to
hear about it.