NOx Sensor Accuracy for O2

Support forum for the NOx Shield for Arduino.
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WarthogARJ
Posts: 4
Joined: 12 Dec 2021 23:46

NOx Sensor Accuracy for O2

Post by WarthogARJ » 19 Dec 2021 22:29

Hi,
What is the accuracy for the Oxygen measurement by the NOx sensor?
Any reports on that?
I cannot find anything on your site or anywhere else that discusses that.

From my understanding of how the NOx dual chamber approach works, I suspect the O2 senmsitivity and accuracy is much worse than that for an equivalent generation Wideband Lambda Sensor.

I say this because the NOx sensor itself is not designed to measure Oxygen very accurately, and only outputs that value as a sort of "afterthought".
It's main purpose is to correct for its effect on NOx measurent (see Sasaki 2010).

The principle of the 2nd gen NOx is to convert all NO2 to NO in the first chamber, with most (but not all) of the O2 being "pumped out".
There is still some residual O2 that goes to the 2nd Chamber, that cannot be measured on its own.

From a commercial engine control viewpoint, you don't need an accurate value of O2 at the urea inection point where the NOx is because you don't use the O2 value at that region for control purposes, but rather use that measured further back by the standard Lambda sensors.

But for a more theoretical understanding, of the final exhaust gas composition it would be useful to know an accurate O2 content downstream of any active exhaust system components.

Thanks,
Alan

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Christian_Bylund
Posts: 255
Joined: 07 Mar 2015 18:09

Re: NOx Sensor Accuracy for O2

Post by Christian_Bylund » 19 Dec 2021 23:51

WarthogARJ wrote:
19 Dec 2021 22:29
Hi,
What is the accuracy for the Oxygen measurement by the NOx sensor?
Any reports on that?
I cannot find anything on your site or anywhere else that discusses that.

From my understanding of how the NOx dual chamber approach works, I suspect the O2 senmsitivity and accuracy is much worse than that for an equivalent generation Wideband Lambda Sensor.

I say this because the NOx sensor itself is not designed to measure Oxygen very accurately, and only outputs that value as a sort of "afterthought".
It's main purpose is to correct for its effect on NOx measurent (see Sasaki 2010).

The principle of the 2nd gen NOx is to convert all NO2 to NO in the first chamber, with most (but not all) of the O2 being "pumped out".
There is still some residual O2 that goes to the 2nd Chamber, that cannot be measured on its own.

From a commercial engine control viewpoint, you don't need an accurate value of O2 at the urea inection point where the NOx is because you don't use the O2 value at that region for control purposes, but rather use that measured further back by the standard Lambda sensors.

But for a more theoretical understanding, of the final exhaust gas composition it would be useful to know an accurate O2 content downstream of any active exhaust system components.

Thanks,
Alan
Hi Alan,

You are right, the EGS-NX2 have a lower accuracy and range of O₂ measurement compared to the LSU 4.9. In our introduction video we compared the specifications of the EGS-NX2 sensor and the LSU 4.9 sensor. You can find the EGS-NX2 Sensor Datasheet on the product page of the NOx Shield.

Thank you and I hope this answers your questions.
Best Regards,
Christian Bylund
Bylund Automotive AB

WarthogARJ
Posts: 4
Joined: 12 Dec 2021 23:46

Re: NOx Sensor Accuracy for O2

Post by WarthogARJ » 20 Dec 2021 18:25

Hi Christian,
Excellent: I missed the info on the O2 details buried in the NOx info.

Yeah, it's tricky when the various sensors use propietary comms, or at least it is for me.
The SAEJ1939 NOx sensor is too expensive for the (relative) limited info it gives me in my application.

I need a reasonably accurate Oxygen value, over a bigger range than the NOx sensor gives.

Maybe I can find a Chinese version.
Or maybe you'll figure out a way to use the cheaper car-based ones....:-}

Thanks for your excellent site.
Alan

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