NBO2 configuration

[fehrudi]

Hi,
I'm new to this forum, so I hope its not problem that I opened a new topic...

I bought a genboard v3.3, the engine started, but I still dont know how to configure NBO2 correctly.

Config taken from here: http://www.vems.hu/manual/html/ch09s07.html but MegaTune reads (fast changing) random voltage (2-5V) when I switch the setting from wide band to narrow band.
When this setting is wide band, it is measuring the EC18-13 pin, and its changing as it should.
It seems that the NBO2 input is the 2nd nernst channel (this is correct in manual), but that is pin EC18-1, not EC18-13...? When I short this pin to ground, then it reads constant 0V.
The random voltage is somewhat related with the EC18-1 pin voltage. As the sensor heats up the initial 2-5V change drops a few V.
I use 1.0.73 fw.
So, what did I wrong?

[rob@vems.co.uk]

Its a tricky one this, as I've never considered using narrow band and havent heard of many others who have.

I can tell you that EC18-1 (as well as EC18-2 & 3) are usually wired to the knock sensor, chances are, if you've not soldered wires in for this that the pins will have no connection at all.  You would be best to rely on the schematic and use that to trace the lines on the board to see where the second nernst channel lives.

[fehrudi]

Thans for the answer.
I tracked back the EC18-1 pin and its connected to U17D then the signal goes to the 54th pin (ADC7) of the atmega - as it is in schematic - and it means that EC18-1 sould be the second nernst channel.
I dont know why this pin stated as knock sensor 2 signal...
This whole thing is weird because my multimeter shows constant voltage at ADC7 pin, while in MT reads random voltage.
It seems that this is not a simple problem, so maybe the best I can do is to wait for the WBO2 sensor to arrive...

[fehrudi]

I found why MT reads random voltage...
If you look at the schematic you can see that booth of the nernst channel is connected to the OC2 (atmel pin 17) thru a resistor and a cap.
On that OC2 pin, there is a ~3,5kHz squre wave.
Now I wonder why it needs that squre wave? Is that needed for WBO2?

Would it be good, if I put a pulldown in the O2 signal path, then the opamp as a buffer, after that an RC filter?
This would be something similar like in V2.2 (In V2.2: O2 input pin -> pulldown resistor -> RC filter -> ADC input.)
The input pin is EC18-1, that is sure.

One more thing: maybe I got this "problem" only because the (heated)sensor can not warm up to the operating temperature on test bench? Maybe after it reached that temperature this squre wave won't bother anything...