toyota 02 SAE paper

[xxalexx at ix.netcom.com]

> From:          garfield at pilgrimhouse.com
> To:            diy_efi at efi332.eng.ohio-state.edu
> Subject:       Re: toyota 02 SAE paper
> Date:          Thu, 12 Mar 1998 08:15:42 -0800
> Organization:  Pilgrim House
> Reply-to:      diy_efi at efi332.eng.ohio-state.edu

for spread sheet to calculate temp. and pressure dependence 
the equation is  I = C*D02*(P/T)*(S/L )* ln(  1 / (  1-(Po/P)  )   )
I	current
C	constant=4F/R	F=faraday constant	R=gas constant
DO2	diffusion  coef of oxygen in atmosphere = 0.178
T	absolute temp.
S	electrode surface area
L	length difusion layer
Po	oxygen partial pressure in atmosphere 
P	absolute pressure 

> >Instead of measuring voltage across the electrodes like regular 
> >sensor a  constant voltage of 0.5 +-0.2 is  applied and current 
> >measured. The graphs show:
> >a/f	 current (mA)
> >11	-12
> >12	-11
> >13	-6
> >14	-2
> >14.5 	0
> >16	3
> >18	7
> >23	13   
> 
> Very promising; I dumped those numbers into excel and what I see doesn't
> look very kinky at all. Each of the two legs on either side stoich look
> like they could easily be linearized with a few segments of piecewise
> linear opamp approximation. Both legs look like they have significant
> spans/segments of almost linear shape, until you get fairly far away
> from stoich. These days with 4 opamps per chip, it takes only a few
> parts to match the curve if it's nice and reasonable, like this one
> appears to be, judging from just the numbers above. Good summary. Geez,
> feast or famine. Now it looks like we might have 3 candidates, the
> Bosch, the NTK, and now the ND!
> 
> Now the real question; I couldn't tell from your review comments just
> how Temp sensitive these curves are likely to be. That appears to be the
> only possible fly in the ointment; it sounded like Temp maybe wasn't
> much an issue. Is that correct? If so, this sensor approaches the "too
> good to be true" category. Simple, fairly linear on either leg, there's
> gotta be a gotcha, unless Miss Nature is suddenly and unusually charmed
> by our presence, and want's to "help" us. Heh, NAH!
> 
> Garfield the cynic
> 
> P.S. Anyone have ANY clue as to a part no. for this ND wonder? I guess I
> lead a sheltered life; dunno what an LEV Toy car even IS. Is it their
> new anti-gravity model, that LEVitates? OK, it was just a wild guess.
> 
> 
>