DIY_EFI Digest Sunday, 28 April 1996 Volume 01 : Number 123 In this issue: RE: Honda UEGO Sensor... Re: Honda UEGO Sensor... Re: Honda UEGO Sensor... RE: Honda UEGO Sensor... RE: Honda UEGO Sensor... Re: Honda UEGO Sensor... Re: Honda UEGO Sensor... See the end of the digest for information on subscribing to the DIY_EFI or DIY_EFI-Digest mailing lists. ---------------------------------------------------------------------- From: "Zublin, Bryan (SD-MS)" Date: Sat, 27 Apr 1996 08:35:00 -0700 (PDT) Subject: RE: Honda UEGO Sensor... > Sensor calibration is shown as 1 point cal in atmosphere. Frank, I don't quite understand this statement. Do you mean that the sensor is calibrated with it "measuring" open atmospheric conditions? If so, wouldn't this give a very lean reading as there is approx 22% oxygen in air? As I think about it, the reading in air would be "L=infinity", that is no fuel being combined with air. Thanks for the rest of the info. Bryan Zublin bzublin@xxx.com ------------------------------ From: orlin steven jared Date: Sat, 27 Apr 1996 12:07:04 -0400 (EDT) Subject: Re: Honda UEGO Sensor... > converter with linearization done by the micro. The calibration table could > be stored in non-volatile EEPROM. The parts cost should be less than $50 > ($5 for the uC, $1 for EEPROM, $5 for display/driver, $10 for ADC, $3 for > voltage reference, etc.). If Honda is putting the electronics in their > cars, then the interface cost has got to be reasonable. This would be great. I hope if you pull it off you will make the plans for building the system known to the group :) > A few questions: > 1. Is each sensor calibrated with each interface box? For example, with > the NTK or Horiba boxes, when you replace the UEGO sensor, do you need to > recalibrate the unit? Hopefully the answer is NO. Sorry, the answer is yes. :( Accuracy will be off if you do not calibrate the box after you replace the sensor. I have used the Horiba Mexa 101 and 110 units. For one of these, the sensor is supposed to COME with a factory calibration sheet unique to that sensor. And you use those values in the readout box or something. But, I believe (can't totally remember, it was a while ago) that the other unit requires no calibration sheet, and can be calibrated with the box. Also, there is a quick and dirty way of calibrating these things for o.k. accuracy, but the *real* way of calibrating a UEGO is with test gases, which cost $$$$. I'm pretty sure this is why each Horiba sensor comes with the calibration sheet, so you don't need to calibrate with the gases. But, if for some reason you should ever change sensors, and install a used one, then you would need to recalibrate. Since each UEGO is hand made, there will be variations. > 2. What kind of accuracy do the manufacturers claim for the sensors? And > what accuracy do the interface box manufacturers claim? This project would > require the initial accuracy to be decent, without having to calibrate > (tweak) each unit against an expensive lab standard. Unfortunately, I don't think anyone can give you a really good quote on accuracy without calibration using the test gases. When I tried to calibrate one of these sensors in the lab, I called Horiba, and talked with a technician for a while as he walked me through the 'quick and dirty' procedure. I asked him about the accuracy, and he said probably 5-10%, but he was really hesitant about it. It is a hard thing to say, unless you talk to the test engineers who are testing these UEGOs in the NGK/Horiba labs. Steve ------------------------------ From: orlin steven jared Date: Sat, 27 Apr 1996 12:09:00 -0400 (EDT) Subject: Re: Honda UEGO Sensor... Might I suggest if you're trying to find out more info about the UEGO type sensor, that you check a local patent library for information. The patent sheets contain an astounding amount of information, it is all open to the public, and usually there are some very good photos or pictures. Steve ------------------------------ From: Darrell Norquay Date: Sat, 27 Apr 96 17:00:49 MDT Subject: RE: Honda UEGO Sensor... Bryan Zublin wrote about Frank Parkers comments: > > Sensor calibration is shown as 1 point cal in atmosphere. > Frank, > I don't quite understand this statement. Do you mean that the sensor is > calibrated with it "measuring" open atmospheric conditions? If so, wouldn't This is exactly what he means. The sensor is calibrated to 21% oxygen with it just exposed to air. This is the simplest means of calibration, and it is indicative of maximum "leaness" ie with no combustion at all. Remember that the device is really an OXYGEN sensor, it actually does not measure air-fuel ratio directly, but only infers it from the remaining oxygen left in the spent exhaust after combustion. The sensor has a reference port which is exposed to air, and a measuring port, which is exposed to exhaust gases. The electrochemical cell in between then puts out a signal relative to the DIFFERENCE in oxygen content between plain air and exhaust. This method of calibration only gives you a single point, ie you only have a calibration factor for the lean end. I'm not sure, but it seems to me that if you dunked the sensor in pure nitrogen or some other gas that contained no oxygen at all, you could also calibrate the high (rich) end. This would be a reference calibration only, really you would have no idea what the sensor was doing in between, but you could assume a straight line for approximation. You'd have to get factory cal curves or run your own set of characteristic curves to fill in the blanks and do some linearizing. I worked with a cell much like this a few years back, it was made by GTE Labs but patents were held by a Chinese scientist. It sounds similar in operation, in that you pumped the cell with a constant current and measured the resulting voltage drop across the cell to determine relative oxygen content. The cell I worked with was actually optimized to detect methane in air, but they also made one for AFR applications that could measure out to AFR's of 28 or more. It was used by Waukeshau in the Lean Burn Combustion System for large stationary engines running natural gas or digester gas from biochemical processes. I'd like to get in on this project, it sounds interesting. I'm an analog designer by trade, and I think I still have schematics for the unit I built before. I also have some papers on the principles involved, but I'm not sure they would be applicable to this particular unit without more details on exactly how it works. regards dn - -- - ----------------------------------------------------------------- Darrell A. Norquay Internet: dn@xxx.ca Datalog Technology Inc. Voice: (403) 243-2220 Calgary, Alberta, Canada Fax: (403) 243-2872 "Absolutum Obsoletum" - If it works, it's obsolete - ----------------------------------------------------------------- ------------------------------ From: Frank F Parker Date: Sat, 27 Apr 1996 21:37:37 -0400 (EDT) Subject: RE: Honda UEGO Sensor... > > > Sensor calibration is shown as 1 point cal in atmosphere. > > Frank, > I don't quite understand this statement. Do you mean that the sensor is > calibrated with it "measuring" open atmospheric conditions? If so, wouldn't > this give a very lean reading as there is approx 22% oxygen in air? As I > think about it, the reading in air would be "L=infinity", that is no fuel > being combined with air. > > Thanks for the rest of the info. > > Bryan Zublin I am not sure. I agree on the face of it , it does not make sense. Will try to call next week after a get back from 2 day test @xxx. frank > ------------------------------ From: Frank F Parker Date: Sat, 27 Apr 1996 21:43:27 -0400 (EDT) Subject: Re: Honda UEGO Sensor... > > Also, there is a quick and dirty way of calibrating these things for > o.k. accuracy, but the *real* way of calibrating a UEGO is with test > gases, which cost $$$$. I'm pretty sure this is why each Horiba sensor > comes with the calibration sheet, so you don't need to calibrate > with the gases. But, if for some reason you should ever change sensors, > and install a used one, then you would need to recalibrate. I have access to a mass spectrometer, so I can make up cal gas and measure % O2 in spectrometer. > frank Parker > ------------------------------ From: Frank F Parker Date: Sat, 27 Apr 1996 21:45:47 -0400 (EDT) Subject: Re: Honda UEGO Sensor... > Might I suggest if you're trying to find out more info about the > UEGO type sensor, that you check a local patent library for information. > > The patent sheets contain an astounding amount of information, it > is all open to the public, and usually there are some very good > photos or pictures. > > I have the orginal SAE paper on UEGO and it has block diagram and lots of info but nothing on transfer function or actual interface. Frank Parker > ------------------------------ End of DIY_EFI Digest V1 #123 ***************************** To subscribe to DIY_EFI-Digest, send the command: subscribe diy_efi-digest in the body of a message to "Majordomo@xxx. 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