From what I am reading, the wide band sensor requires feedback from the ECM and the optimal voltage varies between manufacturers. So no way to use a multimeter anyway.
Also, to Pauls point, here is what I found at Innovative Motorsports:
ECU's with NBO2 (Narrow Band) sensors use the sensor only during cruise and idle. They operate by checking if the voltage is below 0.45V, richen up until it is above 0.45V, then lean out, then richen up again and so on. Therefore the mixture oscillates around 14.7AFR. This AFR is optimum for minimum emissions. The oscillations are caused by the operation of the ECU, not by the sensor as many people believe.
This is what I am talking about.. take the electronics out of the equation and consider JUST the sensor. I get a very nice and very responsive voltage change when I adjust the mixture screw with the narrow band sensor and it is repeatable all day long.
