wb-o2 calibration?

[bcroe at juno.com]

Some technical papers researched by the DIY WB 
development group list equations of the sensor
and support circuit performance.  These equations 
include the use of the calibration resistor to 
compensate for variations between sensors.  

The transfer function for the DIY WB ckt is a slight 
modification of the above, and amounts to

                                        2210 + Rcal
Vout = 0.3028 (  ________________  )Ip + 2.5
                                        3580 + Rcal

  Vout in volts, Ip in ma

The function in the brackets is accomplished by a
voltage divider (utilizing Rcal).  If you fail to wire up Rcal
to the board, your output will be too large a swing.
The 0.3028 Ip is accomplished by the Ip series 
sense resistor and differential amplifier.  The 2.5
is generated by the 2.5 volt reference.

Bruce Roe


On Fri, 19 Oct 2001 08:38:13 -0700 Andrew Theurer <habanero at us.ibm.com>
writes:
> I was going through the docs on the ftp site, I can't 
> find any reference to calibrating the ntk sensor for 
> the diy board.  I thought each sensor was slightly 
> different, and at least a free air calibration was 
> required.  How is the sensor calibrated?  
> 
> Thanks,
> 
> Andrew
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