calibration test gas mixtures [was Re: NTK UEGO calibration]

Thu Aug 30 02:32:10 GMT 2001

Warning - this data may have commercial use and may have come from a
commercial source. 8-)

The calibration gas mixtures I posted earlier were by volume (dry).

Another useful data point for O2 sensor calibration is free air (make sure
you have airflow going past the sensor - it is usually recommended to move
the sensor in mid air).

The O2 concentration in dry open air is 20.9% and at 20 deg C (68 deg F) and
62% relative humidity, it is roughly 20.6%.

Jason

----- Original Message -----
From: "David Hunt" <bamainc at home.com>
To: <diy_efi at diy-efi.org>
Sent: Thursday, August 23, 2001 1:49 PM
Subject: Re: calibration test gas mixtures [was Re: NTK UEGO calibration]

> Are these mixtures by mole, weight or volume?
>
> dh
> ----- Original Message -----
> From: "Jason Haines" <jhaines15 at home.com>
> To: <diy_efi at diy-efi.org>
> Sent: Wednesday, August 22, 2001 10:34 PM
> Subject: calibration test gas mixtures [was Re: NTK UEGO calibration]
>
>
> > As promised, here are some sample gas mixtures for different air fuel
> > ratios. These gas mixtures were provided to us by Horiba for use with
our
> > wide band meters at work but they should apply to any wide band meter.
The
> > bubbler is a device (looks like a bong) that is designed to add water
> vapor
> > to the mixture to more closely simulate the gas mixture that would be
> > encountered by an O2 sensor (with water being a natural byproduct of
> > gasoline combustion). You can do this without the bubbler, you just
loose
> a
> > little bit of accuracy.
> >
> > With bubbler:
> >
> > The gas mixture you want for 0.85 lambda (12.5:1 AFR) is:
> >  Carbon monoxide 3.4%
> >  Hydrogen  2.0%
> >  Carbon dioxide 10.0%
> >  Nitrogen  balance
> >
> > The gas mixture you want for .8 lambda (11.76:1 AFR) is:
> >  Carbon monoxide 6.64%
> >  Hydrogen  2.57%
> >  Carbon dioxide 10.0%
> >  Nitrogen  balance
> >
> > A gas mixture for 1.0 lambda (14.7:1 AFR) is:
> >  Carbon dioxide 13.0%
> >  Nitrogen  balance
> >
> > A gas mixture of 13.0 AFR:
> >  Carbon monoxide 4.1%
> >  Hydrogen  0.75%
> >  Carbon dioxide 10.0%
> >  Nitrogen  balance
> >
> >
> > Without bubbler:
> >
> > A gas mixture of 13.0 AFR:
> >  Carbon monoxide 4.0%
> >  Hydrogen  0.733%
> >  Carbon dioxide 10.0%
> >  Nitrogen  balance
> >
> > I don't have a lean (>1.0 lambda) gas mixture specification yet. If you
> need
> > one you can use atmospheric as roughly 20.6 - 20.9% 02. I assume you
could
> > also use a known 02 % concentration gas (with remainder being something
> > semi-inert like nitrogen).
> >
> > You will want to flow the gas past the sensor(s) at roughly 2-3 liters
per
> > minute. You do not want to have any back pressure on the system when
> > calibrating the sensors (although it would be interested to see how the
> > results changed).
> >
> > These mixtures assume normal gasoline. I don't know how much error not
> > having the moisture content or the correct fuel specifications will
cause.
> > If you look at the difference between the mixtures for the 13:1 AFR with
> and
> > without the bubbler, you can see the level of accuracy that is being
> > targeted here. The difference between 4.1% and 4.0% for the CO and 0.75%
> and
> > 0.733% for the Hydrogen. =
> >
> > You will want to get a +/- 1% certified blend but you shouldn't have to
> pay
> > for an EPA certified blend (you don't need that level of accuracy or
> > paperwork). One source for the gas mixtures is Scott Specialty Gases
> > (215-766-8861) - they have offices all over the country. Our tank came
> from
> > Praxair (440-237-8770). I think they also have offices all around the
US.
> > You can get large tanks like those used for welding gases or you can get
> > disposable cylinders but you pay a lot for the disposable cylinders
> because
> > they normally make the larger cylinder in the custom blend and then fill
> the
> > disposables from that so you pay for the extra gas anyway.
> >
> > I hope this if of use to some people.
> >
> >
> > Jason
> >
> >
> >
> >
> > >
> > > > Heater in the WB sensor *will* ignite a propane or butane mix w/
air -
> > > > detonate is more like it.  Did that.
> > > >
> > > > I'm just a minor in chem from 40 years ago, so its a bit
> misty....really
> > > > dunno how these things work.
> > > >
> > > > I used argon/CO2 MIG mix to get stoich; ran a couple of WBs,
compared
> to
> > > > the switching of a NB sensor.  Used a 1 qt Mason jar w/ holes in the
> lid
> > > > for the sensors & small hole to admit gasses.  Convection from the
> > > > heater(s) mixes things well, adding a very small muffin fan didn't
> > change
> > > > anything.  Starting w/ air in the jar (offscale lean), running argon
> in,
> > > > AFRs fall to 14.7:1.  Adding propane or butane at this point is
safe,
> > but
> > > > doesn't take much to *really* swing the AFR rich.  Far as I can
tell,
> > *no*
> > > > O2 and *no* hydrocarbon = stoich - add either O2 or hydrocarbon gas
to
> > get
> > > > the full range of AFRs.
> > > >
> > > > Short of a bomb deal, I couldn't come up w/ a reproducable means of
> > mixing
> > > > known amounts of gasses & come up w/ a 'cal' gas.  These are
available
> > > > commercially, mostly for EPA stuff & come w/ all sorts of assays &
> > > > certificates w/ a price tag to match - try BOP gasses.
> > > >
> > > > Barry
> > > >
> > > > At 04:39 PM 8/21/01 -0400, you wrote:
> > > > >For those of us that are not chemists, is there a cheap way that is
> > > > >also safe (not that I don't like to blow things up as long as I am
> not
> > > > >one of those things).
> > > > >
> > > > >What about Propane?  Or Butane?  Something readily available, and
if
> > > > >so how would one go about testing?  Will the heater in the O2
sensor
> > > > >start an explosion with Propane or other?
> > > > >
> > > > >Where would one get nitrogen or argon?  Is there an easy way to
make
> > > these
> > > > >gases (that is also safe)?
> > > > >
> > > > >Thanks,
> > > > >
> > > > >Steve F
> > > > >
> > > > >-----Original Message-----
> > > >
> > >
> >
>
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