Home O2 Sensor Test?

[stillkotd]

I seem to remember there being a way to test fuel mixture by attaching a voltmeter to your o2 sensor... I just can't find anywhere that explains it for a 4-wire sensor like the one on my '89 325i.

Anyone know how, or have a link to a write-up?

[stillkotd]

Never mind, I found the info I was looking for. Really helpful write up on o2 sensors if anyone is interested: http://www.verrill.com/car/idle/e30_o2test.shtml