O2 Sensor current?

[Teller.John at orbital.com]

O2 Sensors do not draw current (excepting the heater in a heated 02
sensor), they are in fact a voltage source.  Not only that, they are a high
impedance voltage source and therefore do not put out much current at all.
The voltage drop through a 10K resistor is going to be negligible due to
the miniscule currents (less than a microAmp) involved.  To figure the
voltage drop accross your 10K resistor, use Ohm's law (E=I*R) where I =
0.0000002 Amps and R = 10000 Ohms for a voltage drop of 0.02 Volts.

If you want to change the output voltage of one of these devices, you
probably would be better off using an op amp circuit with a gain factor
less than 1.  Any loading of the output of these devices will at best
provide erroneous readings and at worst destroy the sensor.  See the
Forrest M. Mims books which are (or at least used to be) available from
Radio Shock for some examples of these circuits.