Andrieu,
To modify your sensor calibration you need to modify your .sfg file. Export current file and edit using Notepad. Save new file with new unique name. You will need to import the new file back into SV once modification is complete.
The current MAP sensor cal is defined as:
sensor={
id=100434-000
;VERIFIED POLY, FILTER?
function=PRESSURE
pins=C37_P26
; THIS NAME IS FOR A SPECIAL CASE FUNCTION WHICH WILL NOT APPEND "PRESSURE" TO THE END OF THE SENSOR NAME
name=MAP
;The below are in PSI, not inHG, like all pressure senders
min_val=1.25
max_val=29.5
resolution=1
round=.1
is_piecewise=0
low_coeff={
c_x4=0
c_x3=0
c_x2=0
c_x1=5.7752
c_x0=1.2153
}
low_resistance=NONE
low2high_cross=0
high_coeff={
c_x4=0
c_x3=0
c_x2=0
c_x1=0
c_x0=0
}
high_resistance=NONE
high2low_cross=0
window=.2
shift=3
age=16
}
Note the engineering units it outputs is in PSI. Looks like SV converts PSI to inHg later in the process. So first you have to convert .5 inHg to psi. 29.92 inHg = 14.696 PSI. So .5 inHg = .24559 PSI. You did not mention if you needed to add or subtract .5 inHg. So all you need to do is either Add or subtract .24559 to/from the c_x0=1.2153 (intercept). This will shift the slope by the .5 inHg as you desire across the entire range. As Dynon mentioned it may be beneficial to have another reading at the other end of the range to come up with a new slope value (c_x1).
So after you modify your .sfg file you will need to load it into your system. Also remember you will need to load your custom .sfg after every firmware upgrade as it will revert it back to the factory settings.
Good luck,
Kurt
