MAP data...was Re: 48 +1 and sensor data

[John S. Gwynne]

| Anyway - here is some data from a GM p/n 460 6028 map sensor  , i dont know i
| f
| Anyone needs this but .....
| 
| sensor was excited at 4.9956 vdc , vacuum was measured with a manfold absolut
| e
| pressure gage  ( ie inches of mercury referenced to a vacuum - 0 pressure )
| 
| gage                 vout from sensor
| 
| 2.00 in hg         .0048v
| 3.91 in             .2295v
| 5.90 in             .5582v
| 9.90 in            1.3190v
| 15.30 in          2.2785v
| 20.30 in          3.1871v`
| 25.10 in          4.0337v
| 27.40 in          4.4707v
| 29.80 in          4.8863v     barometric pressure so i did not go any higher 
| .
| 
| to get what you would read off of a std vacuum gage, "In of mercury- vacuum "
| subtract the above number from 30.00  ---- ie 2.00 in hg absolute ~ = 28 inch
| es of
| mercury vacuum .Hope it helps someone .
| 
| just thought it might be of interest .
| 
| Jamie Benner



Disassemble of the GM code shows they use 
(MAP A/D COUNTS)/0x2b6*0x10000+0xa57 (decimal at 0x100) to calculate MAP... 

MAP in kPa is 0.36888*count + 10.34 where count is 0-255

from your data....

 meas V  meas P   cal P   error   cal P
  (V)     (inhg)  (inhg)   (%)    (kPa)
========================================
  0.00    2.00    3.08   35.07   10.43
  0.23    3.91    4.33    9.79   14.68
  0.56    5.90    6.17    4.36   20.89
  1.32    9.90   10.42    4.96   35.27
  2.28   15.30   15.77    2.99   53.41
  3.19   20.30   20.84    2.61   70.59
  4.03   25.10   25.57    1.84   86.59
  4.47   27.40   28.01    2.17   94.85
  4.89   29.80   30.33    1.74  102.71

The GM code will also correct for barometric pressure... most 
error is below 20kPa which is irrelevant... looks
like the uncalibrated sensor is within 5% error.

Hey... how about doing that for a two-bar sensor!

john gwynne

note to john....
[z(:,2) z(:,1) (z(:,2)/4.9956*256/0x2b6*0x10000+0xa57)/256/100*29.53]
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