Oxygen sensor as combustion analyzer
#1
12-05-08, 01:24 PM
Join Date: Nov 2007
Location: North Carolina
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Oxygen sensor as combustion analyzer
About a year ago, I recall there was a thread about using an automotive wide band oxygen sensor as a combustion analyzer. Or maybe it was only a link to another site since I can't find anything by searching this forum.
Does this sound familiar or am I just making this up?
Thanks,
Randall
Does this sound familiar or am I just making this up?
Thanks,
Randall
#2
12-06-08, 07:07 AM
I was the one that posted about using a WB O2 setup. For some reason the Search is dead. I was going to find the thread about it for you. Can find a few pictures here:
OilBoiler4
Al.
P.S. also tried clicking on my username to search for my own threads. But that too is dead. Strange.
OilBoiler4
Al.
P.S. also tried clicking on my username to search for my own threads. But that too is dead. Strange.
#3
12-06-08, 07:11 AM
Super Moderator
If you right click on the search function, you should be able to open in a new tab or new window. It will still work there...
Hope you find the old thread...
Hope you find the old thread...
#4
12-09-08, 07:03 AM
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The search function works, though it seems the archives cover only 2008. I'm pretty sure the thread I was looking for was Nov/Dec 2007.
OldBoiler, thanks for the link to the photo's. Googling about for wide band O2 sensors returns mostly info on automotive tuning applications, as you would expect. What I'm looking for is, has someone already designed the circuitry to measure O2 concentration directly from a wide band sensor? I often attempt to reinvent wheels, but I was trying to avoid that this time ....
Thanks,
Randall
OldBoiler, thanks for the link to the photo's. Googling about for wide band O2 sensors returns mostly info on automotive tuning applications, as you would expect. What I'm looking for is, has someone already designed the circuitry to measure O2 concentration directly from a wide band sensor? I often attempt to reinvent wheels, but I was trying to avoid that this time ....
Thanks,
Randall
#5
12-09-08, 07:37 AM
Yep, search is working again. The thread is:
http://forum.doityourself.com/boiler...n-issue-2.html
A WB sensor measures lambda. So the circuitry already exists in the current controllers to measure the O2 concentration. What you are running into is the useful range of automotive use. Once an engine is at 17:1 or higher AFR it generally isn't going to be running. So the automotive use controllers don't convert a high enough of an excess O2 value. Also note how I used AFR, not lambda. This is because hobby auto guys like readings in AFR.
If there was a different lambda to output conversion table in the controller it could easily output a value directly in CO2%, O2%, or excess air %.
A WB O2 sensor such as used in automobiles will accurately measure from 0% O2 through 20.9% O2. And of course also on the rich side of lambda (< 1). Which doesn't really do us much good.
All of the above is why with the setup I am using the controller output is measured with a DVM (as a voltage). And a chart is used to convert that voltage to an O2% & CO2% value.
Al.
http://forum.doityourself.com/boiler...n-issue-2.html
A WB sensor measures lambda. So the circuitry already exists in the current controllers to measure the O2 concentration. What you are running into is the useful range of automotive use. Once an engine is at 17:1 or higher AFR it generally isn't going to be running. So the automotive use controllers don't convert a high enough of an excess O2 value. Also note how I used AFR, not lambda. This is because hobby auto guys like readings in AFR.
If there was a different lambda to output conversion table in the controller it could easily output a value directly in CO2%, O2%, or excess air %.
A WB O2 sensor such as used in automobiles will accurately measure from 0% O2 through 20.9% O2. And of course also on the rich side of lambda (< 1). Which doesn't really do us much good.
All of the above is why with the setup I am using the controller output is measured with a DVM (as a voltage). And a chart is used to convert that voltage to an O2% & CO2% value.
Al.
#6
12-09-08, 11:09 AM
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Thanks! I saw that thread but didn't look through all the posts because of the baffle subject line ....
What are you using for control circuitry for the WB O2 sensor? It seems straightforward enough in principle:
http://www.aa1car.com/library/s_wraf_schematic.gif
but in practice there's a lot of work to do:
TE-WB (vers 1.5) Schematics
which has a lot more circuitry than a flue gas O2 monitor would need, but wouldn't you at least have to have a decent PS for the heater, a precise voltage ref, and a current pump to generate an output voltage?
Thanks again,
Randall
What are you using for control circuitry for the WB O2 sensor? It seems straightforward enough in principle:
http://www.aa1car.com/library/s_wraf_schematic.gif
but in practice there's a lot of work to do:
TE-WB (vers 1.5) Schematics
which has a lot more circuitry than a flue gas O2 monitor would need, but wouldn't you at least have to have a decent PS for the heater, a precise voltage ref, and a current pump to generate an output voltage?
Thanks again,
Randall
Last edited by NJT; 12-09-08 at 07:42 PM. Reason: fixed broked link
