Hi.

I=B4m struggling with this issue for some days:
Using a "pickup coil" that i get from a car relay (310ohm), when i connect
it directly to the ADC i have positive/negative values, but when i connect
the "pickup coil" to a OP-Amp (OPA227) and the ouput from the amp to one
ADC inputs i only have positive values.

This is the results with a magnet using OPA227 :
http://dl.dropbox.com/u/15802004/immm.png

Rudimentary schematic (i=B4m not using any kind of resistor/capacitor in th=
e
amp)
http://dl.dropbox.com/u/15802004/circ.png

I really wish to use the OPA227 because it=B4s much more responsive than
connecting the "pickup coil" directly to the ADC.


Thanks.
Hi.

I=B4m struggling with this issue for some days: 
Using a &quo=
t;pickup coil" that i get from a car relay (310ohm), when i connect it=
 directly to the ADC i have positive/negative values, but when i connect th=
e "pickup coil" to a OP-Amp (OPA227) and the ouput from the amp t=
o one ADC inputs i only have positive values.


This is the results with a magnet using OPA227 :
http://dl.dropbox.com/u/15802004/immm.pn=
g

Rudimentary schematic (i=B4m not using any kind of resistor/ca=
pacitor in the amp)

http://dl.dropbox.com=
/u/15802004/circ.png

I really wish to use the OPA227 because it=
=B4s much more responsive than connecting the "pickup coil" direc=
tly to the ADC.



Thanks.