O2 calibration possible error

[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???

[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.

[800vtwin]

What o2 sensor (controller) ?

[ca434sbc4]

What o2 sensor (controller) ?

None - inject 2.502V into the O2 input.

[Peter Florance]

What o2 sensor (controller) ?

None - inject 2.502V into the O2 input.

What's the value of Vref?

[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?

[ca434sbc4]

What o2 sensor (controller) ?

None - inject 2.502V into the O2 input.

What's the value of Vref?

Good catch Peter Vref == 4.90V.

[Peter Florance]

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.