a different MAF question

[ARTHUR OKUN]

You wrote: 
>
>At 09:38 AM 2/1/96 -0800, you wrote:
>>Has anyone on the list ever tried to splice a MAF sensor into an
>>AFM (Air Flow Meter - Bosch's term for their air vane boxes) ?
>
> YES :)
>
> The AFM (airflow meter vs. HFM for Hot Film airmass Meter) has a 
logarithmic
> output of airflow vs voltage ... LN(F)=b+(Up/Uv)*a
>
> The HFM has a more complicated curve ...
>
> On a MOTRONIC (digital) you can just mung the internal  tables to 
work,
> but on an analog system, you'll have to use hardware to convert ..
>
> Either a uP system, or easier, an 10bit A/D feeding the address lines 
of
> an eprom, with the DATA lines of said eprom feeding a 10/bit D/A ..
>
> Reference BOTH A/D and D/A to the 5v ref out of the L-Jet ...
>
> Jim
>
>ihave even an even simpler methode take  a variable frequency maf 
like gm uses and run that into a simple micro proc like a pic 16
and use a port output driving a cap with a constant current source
to produce the analog output  i bet you the pot in that thing could
be resolved good enough in 100 or so steps
a similar methode is used to tune varactor tuned tv tuners.