Wide Ratio O2 Meter

[garfield at pilgrimhouse.com]

On Tue, 10 Mar 1998 22:23:57 -0700, Land Shark <lndshrk at xmission.com>
wrote:

> Guys.. here's what I think..
>
> Take a look at the HONDA sensor for example..
.....
> Simple.. there is a CALIBRATION resistor that becomes part of the driver circuit
> built into EACH one (in the plug)
>
> Note: Both the HONDA and Horiba/NTK sensors use SEVEN connections.. 
>
>       2 for heater
>       3 for sensor
>       2 for CAL RESISTOR!
>  
>       The Cal resistor is inside the NTK SENSOR, but in the honda one, it is inside
>        the sensor CONNECTOR!
>
> So, somewhere in that masterfully unknown op-amp rich circuit is a single calibration
> resistor which is with the sensor itself

Hmmm, now we're getting somewhere! I just looked at an NTK sensor, and
sure enough, although the sensor wire bundle only has 5 wires, the
connector DOES have 7 pins, just like Jim says, AND, you can see that
those two extra pins are NOT connected to the others (I also measured to
be sure), and that they terminate in a square plastic cavity that's
molded into the connector. I just did a "Thevinin" test on those two
terminals, they are NOT polarity sensitive, show no signs of
capacitance, and read around 3K ohms.

eXcellent factoid, Jim. Oooooh, this is gettin interestin.

Garfield