Re: Leading guestions+1

[Ludis Langens <ludis@cruzers.com>]

Bruce Plecan wrote:
> 
> > Can't find any value for the bias voltage..
> 
> There is at least on some ecms.
> The 148 on the gns I think it was used a .5v where as the others used a
> .440..

The bias voltage should be the same on all GM ECMs, and even probably
many non-GM ECMs.  They all use essentially the same O2 interface chip. 
If you observed any difference, it's because of production variances in
that interface chip and/or the quality of the ground connections in the
system and/or differences in the O2 sensor.

The bias current from the interface chip is also so low that you might
not be able to measure an accurate voltage for it with anything other
than an expen$ive lab in$trument.


Bruce Plecan wrote:
> 
> Anyone happen to know what the max O2 voltage is before the ecm lets the
> smoke out?
> Or what the max O2 diacom will record.

The interface chip is supposed to have a gain of 4.5.  This amplified
output goes to the "5 volt" ADC chip.  Assuming the ADC uses 0 & 5.0
volts as its reference range, the O2 sensor can usefully range from 0 to
1.11 volts.  If the ADC references to 5.12 volts, the O2 can go as high
as 1.14 volts.  (The spec defines full scale to be an input of 1 volt,
with the output to the ADC at 4.5 volts.)

The interface chip is tested to handle input voltages from -1 to +1
volts.  It is designed to handle -3 to +1 volts.  And it lets the smoke
out beyond -3 and +16 volts.

-- 
Ludis Langens                               ludis (at) cruzers (dot) com
Mac, Fiero, & engine controller goodies:  http://www.cruzers.com/~ludis/

----------------------------------------------------------------------------
To unsubscribe from gmecm, send "unsubscribe gmecm" (without the quotes)
in the body of a message (not the subject) to majordomo@lists.diy-efi.org