Wideband and resistance

yea, within the sensor there is a voltage. The signal is current and difficult to mess up.

wrote:

 my understanding is that the "Nernst voltage" determines the current requirement of the pump cell. 

I have never looked into how a wideband works, but Wookie's comment above sounds exactly right to me based on this page:   www.wbo2.com/lsu/lsuworks.htm

This diagram provides a more complete picture of the sensor and the circuit used to measure it.  I also found some actual schematics of wideband reading circuits and they show the same configuration.


As I read it, the VS pin (Nernst voltage) is measured by the controller, and compared to a 450mV reference.  Based on this measurement, the amount of pumping current is adjusted to try to make the VS voltage match the 450mV reference.  The amount of pumping current required is measured and this current measurement is used to determine the oxygen concentration.  

So it's not really fair to say that the sensor uses a true current loop, similar to something like a 4-20mA current loop industrial sensor.  It's definitely more complicated than that, and it's definitely measuring the output Nernst voltage on the VS pin. 

And as you said, your list is the entire proof.

• Measured Nernst voltage
• Drives pump current to null error
• Reads the required current
• Converts current → lambda

The first setup is to measure the Nernst voltage relative to the Vs/Ip wire/pin of the sensor.  If there were an offset or error in the Nernst voltage measurement, that would cause the controller to send the wrong pumping current, and this incorrect pumping current measurement would be used to calculate an incorrect AFR reading.  


 

wrote:

Hello everyone, simple question for you all !! I have stock Coil and Ton’s wire 0ohm with 1kw NGK cap and B8es plugs .. Do my AEM  AFR gauge gonna give me trouble if I dont have at least 5kw resistance? False reading? 
thank you and Merry Christmas 🌲🙂
 

I second Wookie's advice:  "You should ok, just try and ensure your wiring is as far as possible away from the HT leads/plug caps"

I also agree with the initial comment from bry195, specifically referring to the wideband sensor wires: "if you tried your hardest you probably couldn’t introduce electrical noise into the system."

Another potential (but unlikely) issue is that spark noise could upset the internal electronics of the AEM AFR gauge itself.  Modern electronics (the kind that didn't exist in 1980) can be sensitive to radio interference and can be hard to shield.  

So when Wookie refers to "wiring", keep all the wiring away from the HT lead/plug caps.  That would include not just the wideband sensor wiring, but the power supply wires for the AFR gauge and any other modern electronics you might happen to have on the bike.

And as bry195 mentioned, twisting the wires helps to avoid noise pickup, so twist the power and ground wires together.

 

DOHC wrote:

wrote:

 

So when Wookie refers to "wiring", keep all the wiring away from the HT lead/plug caps.  That would include not just the wideband sensor wiring, but the power supply wires for the AFR gauge and any other modern electronics you might happen to have on the bike.

 

I kind of went full overboard on mine because of the electronics and "Lin-Bus" data transfer (screened both looms where they run over the coils and HT leads)