As part of my degree, I will be required to write about a measurement system...lambda sensors then came to mind.

How do they actually work? I'm talking about how it converts the exhaust gases into a voltage that can be used by the ECU...what is this process? What happens after the sensor, does it just go straight to the ECU, or is there something in the middle?

 

Some good info here:

http://www.picoauto.com/applications/lambda-sensor.html

The voltage signal is sent directly to the ECU to be used on closed loop fuelling

It's actually an interesting topic.

Most modern cars now use 2 sensors for feedback, and some VW type cars use widebands as OEM fitment...

 

Useful read

 

Thanks MB...that's really good stuff...interesting read about the contents of a lambda sensor...if you're a geek like me (and obviously Nick as well )

Does anyone know what happens to the voltage once it has reached the ECU? Does it undergo amplification before A-D conversion etc?

 

I think the ECU just uses the raw signal and interprets it as an AFR.

 

Interesting, but I didn't understand why the sensor "flip flops" from rich to lean. Does that mean that the exhaust mixture is changing, or that the exhaust mixture remains the same and the sensor just can't give a stable output?

 

That's the way the ECU works, Dave. It's more efficient for it to do that, rather than try and aim for a set mixture. So the mixture is actaully changing.

Once the car is full throttle, it stops flip flopping and the injectors stay wide open and the fuelling is controlled on pressure, as the injectors couldn't pulse quick enough to time it right.

 

It would have to be converted from A-D though...there isn't clockwork inside that ECU

 

^Great link. I suggest to read this one as well. It includes some information for the lambda sensor.

http://en.wikipedia.org/wiki/Oxygen_sensor

 

Depending on how technical you need to go, this pdf might help (lots of detailed information on the probe itself);

http://www1.tu-darmstadt.de/fb/ms/studium/...LambdaProbe.pdf