Yep I know how it functions but didn't get the frequency issue. Got you know. Although we are now far off topic

I always used just phsysically watching an AFR gauge to determine a lambda's response, as I just learned how it should behave....

So what would a method of testing one be - oscilloscope or fluke? On what wires would you test and what should you see?

 

The frequency is just a question of how often it switches between rich and weak, a lot of sensors in a lot of engines will switch no faster than 1hz. Testing on a scope allows you to measure this accurately, you would test the voltage on the black wire.

Using an AFR gauge is generally more applicable to a wide band sensor in which case you are not necessarily looking for the switching as you can start to look at detailed fueling under load and at ratios other than 14.7:1 which is the thoeretically perfect AFR that the standard lambda refers to.

 

Yup ive had widebands before, for data logging.

I found an AFR gauge on a narrowband was quite useful for 2 things. It was good as a go - no go gauge when on WOT / Open loop as you could clearly see if it was lean or rich (20 point autometer gauge) Combined with a knock link it was very useful. Secondly you could see the respnose time - a slow lambda signal is quite obvious on an AFR gauge.

Interestingly on an impreza, a duff MAF sensor really made the AFR gauge perform oddly. Lights all over the shop!