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O2 calibration possible error
Posted: Mon Mar 15, 2010 7:40 pm
by ca434sbc4
O2 input set for 0V==10.0:1 AFR, 5.00V==20.0:1 AFR
Enable wideband input.
Set 2.502V at C19 = AFR gage reads 15.2:1... Check both my fluke and amprobe meters against each other 2mv difference. Maybe a slight offset in the cal table or???
Re: O2 calibration possible error
Posted: Tue Mar 16, 2010 3:36 pm
by grippo
You are talking about a 1.01% error in AFR, meaning the ECU is seeing 2.53 V instead of 2.50 V. To see whether it is the calibration table (I doubt it - there are 1024 points in this table, so 10V over 1024 gives about .01V resolution.) But i don't know what the table looks like. If you can open the table, you can see what number is at line 512, the midpoint.
Another thing you can do is put the same signal on ADC-7 and see what it reads - that doesn't use a table, just set the knock parameters for 0-5V.
Also, make sure there is no ground offset between your signal and the ECU ground.
Re: O2 calibration possible error
Posted: Tue Mar 16, 2010 7:20 pm
by 800vtwin
What o2 sensor (controller) ?
Re: O2 calibration possible error
Posted: Tue Mar 16, 2010 8:33 pm
by ca434sbc4
800vtwin wrote:What o2 sensor (controller) ?
None - inject 2.502V into the O2 input.
Re: O2 calibration possible error
Posted: Wed Mar 17, 2010 4:05 am
by Peter Florance
ca434sbc4 wrote:800vtwin wrote:What o2 sensor (controller) ?
None - inject 2.502V into the O2 input.
What's the value of Vref?
Re: O2 calibration possible error
Posted: Wed Mar 17, 2010 7:01 pm
by 800vtwin
Gotcha. So it is reading 0.2 AFR too high. Or 0.01v higher than actual input.
What Is your input voltage measured with microsquirt? If that is accurate - its the table error. If the displayed microsquirt voltage is higher - than its an offset. And table is accurate.
Don't know code but If the microsquirt rounded the input voltage up to 1 decimal point than the 2.51 would be 15.2 AFR.
But 0.1v is pretty easy to see in a ground offset. Whats generating the 2.5v? V ref?
Re: O2 calibration possible error
Posted: Wed Mar 17, 2010 7:47 pm
by ca434sbc4
Peter Florance wrote:ca434sbc4 wrote:800vtwin wrote:What o2 sensor (controller) ?
None - inject 2.502V into the O2 input.
What's the value of Vref?
Good catch Peter Vref == 4.90V.
Re: O2 calibration possible error
Posted: Thu Mar 18, 2010 2:56 am
by Peter Florance
ca434sbc4 wrote:Peter Florance wrote:ca434sbc4 wrote:
None - inject 2.502V into the O2 input.
What's the value of Vref?
Good catch Peter Vref == 4.90V.
I remembered that all measurements are relative to Vref
Note to self: I need to check this on systems I build to make sure it's accurate.