Some questions on DIY EGOR schematics

[Marteney, Steven J.]

1) Noticed the use of an op-amp and 7808 for generation of +/- 2.5V by
setting a virtual ground point.  Is this meant to be a 7805?  Splitting an
08 in two would yield +/- 4V rails, correct?   Or, is that circuit just for
simulation purposes in the schematic tool?

2) Also, noted 8V used on pot (R44) to set a voltage.  Seems one could use
12V, or a regulated 5V, since the voltage set point doesn't seem to appear
to be greater than the +/- 2.5V range of the amp (???) (I may be missing
something here.)

3) I assume the ground on the heater schematic page is different than the
ground on the controller page that it is generated by op-amp U1A and the
7808?  (Which makes me curious about yesterday's questions about using a
max232 to generate a negative voltage.  Seems the schematics account for
that with the virtual ground point.)

4) Further adding on to the virtual ground point, it is connected to vs_gnd
on the sensor.  Is the sensor happy with having a system ground potentially
on its case (via exhaust pipe ground) and basically a DC bias on the vs_gnd?
(I don't know anything about the internals of this thing.)

5) The sensor pinout lists the wire colors of 5 pins, which I believe I can
reference to the schematics.  The pinout also lists Power, Ground, and A/F
output.  Are these not used on the sensor (ala 5-pin O2 sensor) or is it an
8-pin connector with only 5 wires coming from it?

6) Is there a datasheet on the sensor used?  I haven't been able to get very
far on the NGK site.  One on DIY site?

This is awesome work!!!  The Excel tables will be infinitely helpful I'm
sure.  Thanks to Bruce, Chad, and all the little guys!!!

Steve (will be giving thanks for the release of DIY EGOR :-)
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