[Diy_efi] wide band O2's

[WopOnTour]

Bruce
Nice of you to chime in
I have found your PWC site very insightful on the intricacies of WBO2 
calibration. Thank You for that. Is your PWC to market yet? I have been 
waiting patiently (like a great many others I'm sure) and religiously 
checking the web-site for an initial group buy. Was there some other way to 
establish when your PWC will be available? If you plan on using an email 
announcement please add my addy to your list wopontour at gmail.com

Now a question if I may, the Bosch ETAS LA-3 is apparently (I'm told) using 
the CJ120/CJ125 controller I had alluded to in an earlier post- did/could 
you confirm that? All indications are that these latest CJ family ICs 
include the most accurate and noise free heater and pump cell current 
controls in an oem (low cost) controller. It doesn't surprise me that the 
Bosch ETAS unit is so expensive, given it's heritage and that it is 
considered a competition grade tuning tool. But this would seem to validate 
the use of these ICs in an oem and ultimately even a potential DIY 
application (if they could even be sourced that is:)
However I would certainly give up on this quest, if I knew that your PWC 
design was getting close to a release date.
Regards
WopOnTour

----- Original Message ----- 
From: "Bruce A Bowling" <bbowling at earthlink.net>
To: <diy_efi at diy-efi.org>
Sent: Wednesday, July 06, 2005 8:25 AM
Subject: Re: [Diy_efi] wide band O2's


> The WB02 subject is a very interesting one. I spent about 7 solid months 
> researching the subject and performing numerous test. There are so many 
> aspects to this whole subject, circuit configuration is just one of them.
>
> Build a gas flowbench and flow some calibration gas over the sensor, this 
> is a real eye-opener. I did not test a lot of meters (but several I did 
> test, I will not post the results because it was not a real detailed test, 
> people should do this themselves), but the one that was the most accurate 
> was the ETAS LA-3, maybe this is why it costs $4K. But there is no where 
> near $4K of parts in it, just a simple '332 processor but real good analog 
> circuitry for the pump, etc. And they use a switcher power supply for the 
> heater (high frequency w/ averaging), this yields a nice clean heater 
> supply voltage without PWM switching noise being injected in the 
> pump/nernst. Heater PWM noise getting into the pump/nerst servo is a real 
> problem, one has to be careful to sample on the same point of the PWM and 
> not during switching.
>
> Garfield Willis did some testing years ago on these, check the archives 
> for his name and see his comments. He held a lot of info to himself, but 
> everything he alluded to I was able to verify independently with my 
> testing, and someone else I corresponded with also came up with the same 
> results. In a nutshell: the sensor (each) needs gas calibration - they 
> tend to vary all over the place, enough that the cal resistor is not 
> enough (concluded from bench testing), the standard calibration curves 
> assume one gas mixture type (this is an issue with nitrous, alcohol, E85, 
> propane, etc), the heater control is absolutely critical (especially when 
> the battery voltage drops low enough not to provide enough voltage even at 
> 100% PWM, this is why both ETAS and the PWC use a switcher supply for the 
> heater), there are significant pump current offsets on both sides of 
> stoich (and they are different, and depend on the particular sensor). And 
> there are things like barometric partial pressure correction, exhaust 
> backpressure compensation, etc.
>
> It all depends on how accurate you want the meter, and under what 
> conditions. The only way to determine if a particular meter is accurate is 
> to measure it with a known gas source. And run the meter with varying 
> supply voltage (like from 8 volts to 16 volts, particularly the low end). 
> The PWC site gives detailed info on how to make a gas flowbench and all 
> other pertinent info (like baro correction and Brettschneider 
> gas-composition PC applications, etc) in order to perform a study of WB02 
> meters.
>
> - Bruce
>
>
> At 12:38 AM 7/6/2005, you wrote:
>>Adam
>>Here is an interesting article on  WBO2 calibration from the Bruce & Al at 
>>Megasquirt
>>http://www.msefi.com/msinfo/PWC/
>>Regards
>>WOT
>
>
>
>
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