Zeus

Is there any way to check that a WB02 sensor is calibrated correctly? I know that you can look at the values while driving and see if they are way off base, but is there anything where you can do "______" and the value of the sensor should be precisely "_____".

I know for example that when calibrating small scales people take a penny or nickle because their weights are already known and don't vary much. Is there a similar thing for o2 sensors? I have heard unlit propane should give a reading of 14:1, but I am skeptical.

BLK02WS6

iTrader: (2)

Most widebands have a calibration mode where they do a free air calibration. They will read exactly the same in the open air - I think it is 20.9

Zeus

I know about the free air calibration, but my problem is this: a free air calibration just tells the Wideband that whatever voltage it is seeing at the moment is that of pure air.

I had issues with my wideband over the past few days where I did a free air calibration several times (took the sensor out of the pipe and everything) but the reading in both LogWorks and on a DMM was CLEARLY wrong. I mean either pegged below 7.4AFR all the time, or pegged above 20.9 all the time, etc. I eventually traced it down to a "ground" wire that for some strange reason had 5V going through it, but basically the free air calibration didn't tell me the sensor was off. It just told the sensor "this voltage means it's in pure air, adjust accordingly".

I'm looking for a way to do a sanity check on the WB02. Meaning is there a gas or something that will give a standard AFR if blown over the sensor?

BLK02WS6

iTrader: (2)

Oh, I see what you are saying now. Sorry, don't know.

jimmyblue

iTrader: (11)

There are reference gas samples that are used for test/
calibrating O2 sensors. $100 can of stale air, anybody?
(I have no idea of the actual price but I bet you wants
none).

Zeus

I was hoping more along the lines of propane, butane, MAP, or what not. Oh well.

ringram

But a wideband measures air, not propane or butane etc.
So you need to calibrate it to air.
If you want to run it inline with a methonol engine etc you can check its reading right, but the only way to calibrate it is to reference it against what its measuring.
Calibrating and measuring are the key concepts IMO

oange ss

iTrader: (50)

which ground is gettin the 5V signal ?

Zeus

I'm sorry, I thought it measured the amount of fuel in a given stream of gas. If it really does read off o2, what about immersing it in a stream of nitrous? You know the chemical composition of nitrous is N20, therefore you also know the AFR. This is unless it measures O2 molecules, or if the oxygen needs to be unbound.

Zeus

I took my switched 12V and ground from one of the rear O2 sensor harnesses. I put a DMM on the terminals before soldering anything, but I guess I messed it up somehow. The really strange thing is the WB was working perfectly and then one day the ground decides to get 5V going through it. I didn't touch the wiring or anything.

jimmyblue

iTrader: (11)

From everything I've read the NBO2 and WBO2 are both
oxygen-transport "fuel cells". The partial pressure oxygen
difference across them is what makes the voltage. You
need free oxygen, not bound up in N2O or anything else.

Looks like people use 0% - 10% oxygen reference gasses
to calibrate WBO2s...

http://cafee.wvu.edu/Assets/Document...0Operation.pdf

But the curve is very nonlinear and I think calibration
would be a real "science project"...

http://wbo2.com/lsu/default.htm

PLX devices is all proud about not needing (allowing)
recalibation. Personally I find this pretty questionable
from a "what do you do about sensor aging?" view.
But they do mention that elevation in particular can
skew free-air calibrations...

http://www.plxdevices.com/AppNotes/P...Technology.pdf

P Mack

iTrader: (6)

I've found that during normal driving when my car is in closed loop my wideband is very close to 14.7 as it should be.

jimmyblue

iTrader: (11)

If you have good, already-functioning closed loop
operation then this may in fact be your best bet.
Just set the thing up with a bit of smoothing in
there to eliminate the chatter, and you should see
the magic number. The narrowbands are trying
their best to make your 14.7:1 reference gas.

May not help if you're way out in the weeds with
the mixture loop open or comatose O2s though.