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Old 07-24-2003, 02:03 PM   #35
Jon [in CT]
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Member#: 2992
Join Date: Nov 2000
Chapter/Region: NESIC
Location: Connecticut, USA
02 WRX Sedan


Originally posted by 8Complex
Was this taken off of the site somewhere? There is almost no data on the unit there that I could find, but this would be excellent information (that somehow I missed before).
8Complex, that info was derived from their well-written user's manual, available at their site via the "Support" button.
Originally posted by Klaus
5. Pressure compensation
The measurement method we use and have applied for a patent indeed does allow to theoretically compensate for exhaust pressure. Unfortunately the Bosch sensors have a temperature dependent parasitic resistance in the virtual ground of the pump/Nernst cell. This interferes with our pressure compensation by simulating exhaust pressure changes when there is in actuality only a change in sensor housing temp. We are working on a software way around that so that you can download it later to the meter. This is a try, not a promise.
Until now, I'd never read about any electrical property or relationship of either the sensor cells or their heater that varied with a change in gas pressure but didn't vary with a change in partial oxygen pressure or gas temperature. Finding such a property or relationship certainly deserves a patent and I eagerly await the publication of the patent application. I hope that among the patent's claims is the ability to use an oxygen sensor as a surrogate pressure tranducer in the exhaust stream. Although there appear to be some problems getting this technique to work well with the Bosch sensor, I take it that LM-1's pressure compensation technique DOES work well with the NTK sensor?

Originally posted by Klaus
Because the Bosch sensors are much more temperature dependent than for example the NTK the accuracy will greatly suffer. The NTK on the other hand is less temperature sensitive but much more pressure sensitive than the Bosch, so it will suffer more from pressure induced inaccuracies.
Is the LM-1's temperature compensation technique able to more-or-less eliminate any difference in temperature dependence between the NTK and Bosch sensors? On the other hand, even though the NTK sensor signal is inherently more pressure dependent than the Bosch, given that the LM-1's pressure compensation technique doesn't yet work well with the Bosch, does using the NTK with the LM-1 result in less distortion due to pressure variations than when using the Bosch with the LM-1?

Originally posted by Klaus
The minimum lambda is sensor dependent. In case of the Bosch it's minimum is about 0.65 lambda.
What is the minimum lambda (richest A/F ratio) that can be accurately detected by the NTK sensor?

I guess this entire post is leading to the question: If one could use either the NTK or the Bosch sensor with the LM-1, which one should be preferred?
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