Quote Originally Posted by CV8IIM6 View Post
I've had a bit more time to look properly at the log with the voltage spikes in it and to play around with my DM-100.

Firstly in the log i can see regular spikes (21 in a 12 minute log) to AFR's of 12.5 17.5 and 10 which just isn't plausible.

I decided to set up the DM-100 to display a warning when ever measured AFR is less than 10.1 I then went driving with the V2 not even connected. It was disappointing to see the warning displayed on a reasonably regular basis confirming an issue with the PLX SM-AFR not the V2 or software.

So I'm wondering if i have a poor earth, if the unit was faulty, if my modifications have damaged a component, if my converter chip is faulty etc.etc.

I'll run a new earth, check my connections inside the unit and have a look at the analog output to start with.

expensive experiment at this stage.
I too have noticed these spikes on my modified SM-AFR. I remember the DM5 gauge also has these spikes. Betting the spikes on the display correlate with the spikes on the serial output.