Oxygen Sensor transfer function? 1

[NickB]

I'm trying to find data sheets or anything at all with a transfer curve relating lambda or air/fuel ratio to voltage output for a standard automotive type switching oxygen sensor. Any manufacturers datasheets on wideband UEGO sensors would be nice too.

I'm working on a circuit to give a useable A?F reading from the standard type of sensor, as the widebands are so expensive.

 

[nimpoc]

Dude,

http://www.diy-wb.org

It's awesome.

MK

 

[NickB]

Yeah, i've seen it, and i really like it. I'm working on this for some guys who don't want to spend the $160 on the sensor though, and just run it off their stock sensor.

 

[NickB]

I was planning on feeding a D/A converter with the O2 sensor voltage, running to the address lines of a small eprom. The data in the eprom would be a two bit BCD code with a "1" placed in front to give an A/F reading from 10.0:1 to 19.9:1. It would be quite low cost, and work with a standard O2 sensor, and provide reasonable accuracy compared to the usual bargraph type A/F gauges and would give a useable A/F ratio rather than just a voltage.

Ideas/comments?

 

[carnage]

O2 sensors are fancy thermocouples from what I understand so keep in mind that it is very nonlinier. also since it is very low current you will need to have it as well shielded as possible.

 

[NickB]

Oh, they're VERY non-linear, i already knew that. They don't work like thermocouples, though there is a slight thermocouple effect that creates errors. The voltage is created by oxygen ion diffusion through a titanium dioxide cell.

 

[carnage]

Do you know where to get the equasion or the lookup tables required. I would be very interested. Thanks.

 

[NickB]

That's exactly what i'm looking for myselt. So far, the best info i've found is:

http://www.huntleyracing.com/o2sensordatasheet.htm

I'm sure it's just a standard oxygen sensor, as it has the same transfer curve shape as the rest of 'em. If i can't find naything better, it'm going to plug these values in and see what it comes up with. Until now, i've just been watching the voltage with a good multimeter, and i can even see when the computer switches from the part throttle fuel maps to the full throttle maps when the O2 voltage jumps from 0.780 range to 0.900 range. I'm thinking i have to richen up the part throttle fuel maps to match the full throttle maps when it's under boost, or BOOM at higher boost pressures.

 

[stevieturbo]

There are a couple of wideband options. The bosch and NGK EUGO sensors. Does anyone know what the differences are?
A useful link is

http://www.techedge.com.au/vehicle/wbo2/default.htm

I purchased a kit form here, and it seems to work well. Although I would like a little more info on the sensors as apparently a wideband sensor is supposed to come with external electronics? I have recently fitted a engine management sysstem to my car which has a fuel map based on lambda/AFR target mixtures, but i need the correct sensor to make it work properly. Just not exactly sure which one as I used a NGK UEGO sensor for the DIYWB, but i bought the sensor only. Not sure where to get the control box I have been told about ( by the suppliers of the management system )

 

[carnage]

would this work better with a capacitor to even out the readings to give a more linear reading as opposed to a very "spikey" reading?

 

[NickB]

Adding a capacitor won't make it more linear, it will simply dampen the response, making it inaccurate. The only way to linearize the transfer function of a standard O2 sensor is to run it through another transfer function designed to make it linear.

 

I am loocking for a Oxygen sensor for my Honda Civic LX year 2000.
Are Bosh or NGK or NTK equivalents?

 

[NickB]

The factory sensor is very likely an NGK/NTK sensor. Just match up the right number of wires, and you shouldn't have any problem. The connector may be different, but the wires still do the same job.

Unless you've got the 5 wire sensor (7 wires on the harness) you shouldn't have any trouble finding a low cost replacement. If it is the 5/7 wire sensor, then it's going to cost you.

 

[MickT34]

the formula for sensor voltage can be found on this link

http://www.nernst.de/lambda-sensor.htm

I have a couple of ntk lambda sensors that I'm trying to find data sheets on, any ideas?