[Diy_efi] Patent 6120677

[Bernd Felsche]

Perry Harrington tapped away at the keyboard with:

> On Sat, Jul 13, 2002 at 12:43:15PM -0500, bcroe at juno.com wrote:
> > Nice work.  I'll need to look at this more.  Apparently they pulse 
> > the Vs cell briefly to determine its impedance, finishing with a
> > mirror image pulse to get it back to its original mission quickly.
> 
> Read that part again.  They pulse the Ip and Vs at the same time,
> but out of phase.  This way the 2 cancel eachother out.  They
> do not require a settling time after this.  I believe Bernd does a
> very similar thing, but he's not pulsing both sides and thus requires
> a settling period.

Read the section on Cell Temperatures again. The "settling period"
as you call it, is inevitable. A current reversal to cancel the
imposed charge by the forward current _reduces_ the recovery time
from about 16 to 0.5 milliseconds. Recovery is not required on the
pump cell because that cell's EMF isn't used to measure gas
concentration.

> This brings up another interesting point.  Since the Ip pump and
> the Vs cell are both Ziconia, one used as a pump and the other a
> sense cell, what would happen if you did 'purging' of the cells
> periodically?

AC-drive on the pump cell does so "continuously". It avoids the
situation of "plating".

It's difficult to "purge" the Nernst cell. It's bounded by the
pump cell on the exhaust gas side and by the reference cell on the
other. 

> Seems like it might be a way to fight sensor contamination.


-- 
/"\ Bernd Felsche - Innovative Reckoning, Perth, Western Australia
\ /  ASCII ribbon campaign | I'm a .signature virus!
 X   against HTML mail     | Copy me into your ~/.signature
/ \  and postings          | to help me spread!

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