Bosch to Hitachi Maf

[tom cloud]

>    Thanks for the advice on how to invert the signal.  The second part of 
>    my question related to some type of manual adjustment of the signal.  
 [ snip ]
>                                        Assume that we have measured 
>    the voltage output of both units at 10 and 220 CFM (assume air 
>    temperature is equal).  The Bosch puts out 4.7v at 10, and .3 volts at 
>    220 CFM.  On the other hand, the Hitachi puts out .5v at 10 CFM and 
>    3.6v at 220.  I'd like to have a programmable device that could convert 
>    the two, interpolating the voltage signals between the actual measured 
>    values (in this example, only two).

If you'll build the inverting amp I drew, I think it'll fix the prob
for you -- then you can get rich selling it.

First, determine the difference in the ranges -- that's the gain.
On the drawing I sent, gain  A = R2 / R1.  So, say you want 100k
Zin.  Then R1 = 100k.  Say range of input is 4 volts and the range
wanted out is 5.  Then the gain is 5/4 and R2=(5/4)R1=500k/4.

But, what if the desired output range is smaller?  Sameo-sameo.
Assume in=4 volts delta and out = 3 volts delta.  Then
R2=(3/4)R1=300k/4=75k.

Now, all you gotta do is set the offset pot so that the output
range starts and stops at the voltages you want.

tom