* Bridge offset is: -60mV to +30mV at 8V Vbridge
We assume we can divide it by 8 which gives -7.5mV/V to +3.75mV/V
At Vbridge = 5V, that's -37.5mV to +18.75mV
Assume that our temperature range is -40 to 80 degree C
This gives +-20% change at -40 degree C which means our absolute worst case offset is -45mV to +22.5mV (5V Vbridge)
Because we're so conservative, we take 50mV to be our worst case.
* Sensitivity (max): 4mV/V/Gauss
Assume the maximum magnetic field is 650mGauss.
Thus the max sensitivity is 13mV (5V Vbridge)
Vout (worst case): 63mV
Assume output centers on 2.5V and assume we want to stay away from the rails about 50mV, then our gain is
(2.5 - 50mV) / 63mV = 38.8
Go with the old route for now which is zeroing out the offset through the offset strap.
--- 30 Jun 2004