Looking for low-cost ignition analysis 'scope

[John T Stein]

 ferguson at srcing.login.qc.ca (Lloyd Ferguson) wrote:


> This is something I have been wanting to do for a while as I find it
> fastinating that you can assess an engine's condition just by looking at
> the spark waveforms.
> 
> I have tried he approach of using a "Lab" scope with the inductive pickup
> from my timing ligt for trigger and a piece of metal over the coil in the
> middle of the GM HEI distributor (this is the way the Heathkit analyser
> works as well as other prfessional units I have seen). The interfacing is
> not a problem, where I ran into problems is that the repitition rate of the
> signals from the engine are so slow at idle that the scope does not have
> enough persistance to keep the display on the screen.  When I did this
> (about 10 years ago) I used a Tek 465 100Mhz scope maybe a lesser scope
> would be better but I doubt it because the signal is pretty slow (600 RPM =
> 10 RPS /2 = 5 triggers per second).
> 
> As for the calibration, I purchased a manual for the Heathkit unit when I
> was thinking about this and they clamped the pickup around the high-voltage
> lead to the CRT for calibaration, not very usable on another unit. I was
> going to address this if and when I got it working.
> 

Sometime in the distant past Tektronix published a soft-cover book 
discussing the use of oscilloscopes (theirs, of course) for the 
analysis of  internal combustion engines.  If I remember correctly it 
had a good treatment of ignition waveform interpretation.  You may be 
able to get a copy from a local Tek rep.  It was part of a very good 
series of 'scope-related texts they had.


> I have been milling around an idea of trying a cheap sound-blaster type
> card with an analog input to digitize the signal and then using one of the
> graphical audio editing packages to display it (perhaps doing the whole
> thing on an old 286) any comments?

A number of firms; e.g. Keithly, MetraByte, National Instruments make 
relatively inexpensive analog I/O cards for the PC. They usually 
come with the necessary "c" and/or BASIC drivers.  This would seem to 
be a very flexible solution to getting the date into the computer in 
a form ready for analysis

John.