GMECM Digest V2 #964

[Len Sabatine]

   It's simplistic, when the need is there , braided shield grounded on 
both ends.
   I use the engine block . These shield[s] aren't always required. I don't 
like to
   employ any additions unless there's a problem. A scope will show the spikes.
   Len


>Hmmm... interesting difference in the results, which I suspect is due to
>the differences in wiring of the two cars. I guess we will have to try it
>both ways. It would be helpful to know the characteristic impedance of the
>shielded line used. If you have any idea of this I'd like to hear it.
>
>Len, did you ground the shield at the ECM end, and if yes, did you connect
>the shield to the ECM housing or to the O2 input ground terminal? My
>application is with a 730 ECM. As I recall, the schematic in the archives
>shows a simple RC network at the O2 input of the ECM. Do you have any idea
>what the R and C values are?
>
>Don
>
>
>Joe said...
>
> >I've had good luck with braided shielding in other applications
> >(specifically, fire and gas detection systems), but it is very critical NOT
> >to ground both ends.  The shield needs to be grounded on one end and the
> >other protected by heat shrink or any method to prevent it from creating
> >another ground path.  What happens is the creation of an antenna.  I missed
> >putting heat shrink on one end of a cable and only a few wires from the
> >braid touched the conduit.  When a portable radio was brought into the
> >vicinity and keyed - the system tripped.  It turns out that no shield is
> >better than one grounded on both ends (in my experience anyway).
> >
> >Joe
>
>
>Len said...
>
> >>      Braided ground shield seems to work best , both ends grounded.
> >>      It does help remove any Rf garbage from the signal .
> >>      A Scope will show how much trash is present in the general area.
> >>     There's filtering built into the ECM for this purpose as well.
> >>      Len
> >>
> >> >I posted this a week or so ago but apparently the server was down so here
> >> >it is again.
> >> >
> >> >Many months back some posted a comment to gmecm about shielding their O2
> >> >sensor wire to eliminate a problem with ignition noise. If you are still
> >> >around I'd like to hear more about what you did. Shielded cable
> >impedance?
> >> >Length? How the shield is grounded, one end or both ends?
>
>
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