Wide Ratio O2 Meter

[Land Shark]

At 07:52 PM 3/10/98 -0800, you wrote:
>What is the big problem in desigining a meter for one of the sensors? Is it
>the calibration that must be done, because at a worst case I'm thinking of
>a simple op-amp buffer (high impedance) connected to a pic or some other
>CPU that has a way to calibrate the sensor and drive a LCD or something. Am
>I way off? If not get me some spec on the electrical requirems or the
>various sensors and let me have a look. Not that I have time, but what the
>heck, we may want to use this some day when the I/O boards get a work out...

 Guys.. here's what I think..

 Take a look at the HONDA sensor for example..

 It's MASS PRODUCED.. but it has the ablility to do fine control off of stoich??

 And you can interchange them until your hands get tired..

 Why??

 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

 Jim