Back to your original comment of "using the air in the wires"
Umm... No. That's not what happens. The sensor produces approximately 0-1volt depending on what the air fuel ratio is. It's all in the metal sensor. Then it outputs a reference (ground) and a signal (0-1v) and the other two wires control the heater. Some older years only have 3 wires, two being heater and one being signal. The wires have nothing to do with the a/f ratio unless the crimp connector starts corroding and changes resistance of the signal or ground wire. That's why you solder them using higher quality wire, to reduce the resistance of the longer wire. The "air in the wire" has nothing to do with anything.

 

An O2 sensor does not measure the amount of oxygen in the exhaust. It makes a comparison between the inside and the outside of the bulb in the sensor. This is how it creates the ~1v. The sample air on the inside of the bulb is retrieved through the wires. Older style O2 sensors had a hole in the body for this, but it was eliminated to end premature failure of the sensor due to contamination.

Also, as a side note, an O2 sensor does not measure air fuel ratio. You need a lambda sensor for that.