Sensor Linearization

peter paul fenske pfenske at direct.ca
Fri Jun 14 03:01:28 GMT 1996


>If you have lots of PROM space, one fast way (cpu cycle wise) to linearize
>the MAT or CTS is to have a 256 byte look up table representing the complete
>temp range of the sensor.  Get the A/D result for the sensor, and move it to
>ACC B.  Point the INDEX to the start of the table, add ACC B to the INDEX,
>and get the value at the new INDEX loc that represents the temp of the
>sensor.  Quick and easy once you establish the table.
>
>As far a the MAP sensor, I have plotted the output of several MAPS, using a 5
>volt ref, a voltmeter, and a hand held vacuum pump.  These things are amazing
>linear!   They don't go all the way to 0 volts, or all the way to +5 V, so
>the output only uses a portion of the available range.  Just subtract a
>nominal minimum position from the output to get to zero, then scale what
>would be the max range of the sensor to be the max output that fits in '00'
>to 'FF'. 
>
>Scot Sealander  FIScot at aol.com
>
>Hi Scot:
>Yes I have thought of the bruce force method but have dismissed it 
>so far in dealing with the Map. Proms are cheap though.
>True both TPS and MAP are linear sensors with an offset. I just
>find doing all the calcs takes up a lot of cycles. Once again
>the response that there is considerable head room in processing
>time is correct. It is relatively simple to do the calculation.
>My training is in small MPUs where everything had to be optimized.
>Maybe I should relax that a bit.
>Tnx Scot: peter




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