cheap EGA

[Tom Cloud]

>Looking for a source (retail) for a cheap lean-stoich-rich exhaust gas
>analyzer, the O2-sensor-and-LED variety.  I believe the name Cyberdyne
>and the price $30 have been mentioned... vaporware?  Anyone know who
>carries this or one like it?  
>
>thanx,
>Ed Mellinger

Ed, this topic comes up periodically.  I routinely
slam those little devices because they're notoriously
inaccurate.  But, OTOH, they are quick and do yield
some data -- albeit it questionable.  They should
be accurate at stoich -- they absolutely are NOT off
of it -- but you can get a seat-of-the-pants feel
for what's going on, even if the data is inaccurate
(i.e. it may not be 16:1, but it IS lean!!).  So,
my amended opinion -- it's vaporware that can give
useful information if you know that that's what it
is -- i.e. know its limitations.

You can make your own too.  RatShack used to have
LED bargraphs, and Mouser, Digi-Key, et al do have
them, that take zero to one volt or so as an input.
All you'd have to do would be to use one of them
would be an op-amp buffer (to achieve the needed
high impedance required by the EGO) and a voltage
divider or gain/attenuator circuit to drive the
LED bar-graph.  Total cost including EGO should
be less than $40.

Tom Cloud <cloud at peaches.ph.utexas.edu>