tolerance analysis of resistive method.

["Rick Brooks" <ribrooks@xxxxxxxxxxxxxxxxxx>]

Title: tolerance analysis of resistive method.

Happy New Year to all
is this the first reflector email of the new millennium?

I just wanted to make everyone aware of a tolerance analysis that I did
regarding the two point resistive method of discovery.

There are two Thevenin voltage sources, V1 and V2 (the two probing voltages).
Ideally V1=24V and V2=12V, so V2 = 0.5 * V1.

The analysis looks at the worst case tolerances of:
the 75K source resistor res_tol,
the tolerance of the 1st source V1, src_tol,
and the tolerance of the 2nd source voltage V2 relative to the 1st source voltage, this is called src_rel_tol.

I start with the desired valid signature range of 19K to 26.5K.
Then I derive what the window detector voltages must be in order to guarantee that a valid signature will
always be correctly recognized.
Then, given those defined window detector voltages, I again use worst case tolerances to determine
what range of signature resistance will be guaranteed to be rejected.
At present, it looks like tolerances of around 1% will be needed, or we will need some
form of calibration, or maybe we will need to change signature values,

Check the analysis file out at:
http://www.ieee802.org/3/af/public/documents/tolerance_analysis.pdf

see you in Irvine,
- Rick