Smog machine info

[John Hofstetter <hofs@domain.elided>]

>John:
>
>Probably not as far fetched as it might seem. Those of us subject to
>smog inspecitons have been amazed at the machines they use. And, because
>they keep uping the requirements, the older, obsolete machines are for
>sale for a few hundred dollars all the time.
>
>One of the features that amazes me is, they put a "sniffer" in your
>tailpipe and a inductive clamp on your #1 cylinder wire. From this
>alone, these machines will give you engine RPM, real time ignition
>advance, and of course, HC PPM, CO PPM , NOx PPM, CO2% and O2%. How do
>they get real time advance from one spark signal? I know that RPM is
>just a formula based on the number and frequency of plug firing.
>
>Tom H.

Tom and others interested in the subject:
Son John says that you are short at least one sensor lead, Tom. What you 
have stated can't work, which is what you already decided but didn't 
trust your own good judgement. 
John H.