[Diy_efi] Continuing the chip switcher "problem"

Wed Feb 16 21:30:50 GMT 2005

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Marcello,

I think Bob Hughes has this one correct.  I flagged aliasing as a  probable 
cause of the "problem" some time ago.  Your DSO is deceiving you -  it's not 
"seeing" the ground potential because it doesn't stay there long enough  for the 
'scope to pick up.  I suggested you get something 100 times faster,  I think. 
 What you see is what the 'scope makes of things after the  anti-aliasing 
filter has finished with the waveform.  Remember that  transitions to ground are 
the exception, and they are brief.  They aren't  presented long enough to show 
on screen.

Your ECU is clearly working properly, so the correct signals must be there,  
but equipment limitations prevent you seeing them.

Will Cowell

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<DIV>Marcello,</DIV>
<DIV>&nbsp;</DIV>
<DIV>I think Bob Hughes has this one correct.&nbsp; I flagged aliasing as a=20
probable cause of the "problem" some time ago.&nbsp; Your DSO is deceiving y=
ou -=20
it's not "seeing" the ground potential because it doesn't stay there long en=
ough=20
for the 'scope to pick up.&nbsp; I suggested you get something 100 times fas=
ter,=20
I think.&nbsp; What you see is what the 'scope makes of things after the=20
anti-aliasing filter has finished with the waveform.&nbsp; Remember that=20
transitions to ground are the exception, and they are brief.&nbsp; They aren=
't=20
presented long enough to show on screen.</DIV>
<DIV>&nbsp;</DIV>
<DIV>Your ECU is clearly working properly, so the correct signals must be th=
ere,=20
but equipment limitations prevent you seeing them.</DIV>
<DIV>&nbsp;</DIV>
<DIV>Will Cowell</DIV></FONT></BODY></HTML>

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