[Diy_efi] Interesting quandry regarding UEGO patent 6120677

[Perry Harrington]

Hello all,

I was reviewing the said patent and have a interesting quandry.

The figures 5A and 5B are very interesting, as they graph pump & EMF element
impedance against heater voltage.

The obvious reason to do impedance sensing on the EMF cell is to control the
heater more accurately.  However the patent leaves out some very important
information.  Namely the temp transfer curve for the EMF cell.  One could
infer they assume that the heater temp is the same as the EMF temp.  This also
implies that the impedance of the heater is not an accurate measurement of
the heater temp.

The other thing that this graph shows (and the accompanying details) is that
the AFR has no effect on cell temp when high PWM frequencies are used to sample
the impedance.

>From this data I posit this:  You do not have to sense cell impedance if you
can generate a more accurate heater temp transfer function *AND* you use a
sufficiently high PWM frequency for controlling the Ip pump, specifically > 1khz.

Please feel free to discuss this.

--Perry

-- 
Perry Harrington			Data Acquisition & Instrumentation, Inc	
perry at dainst dot com					 http://www.dainst.com/

Those who would give up essential liberty to purchase a little temporary safety
deserve neither liberty or safety. Nor, are they likely to end up with either.
                             -- Benjamin Franklin

_______________________________________________
Diy_efi mailing list
Diy_efi at diy-efi.org
http://www.diy-efi.org/mailman/listinfo/diy_efi