Gee, Alan. We were just discussing this the other day when I explained to you the technique to approach these sensors without need of a differential scope. Good explanation.
Here is some more on that....Math channels are so cool.
Your EDIS system has a floating ground CKP and a non floating CMP.
To review...The EDIS CKP is a VRS two wire sensor with no ground reference. In the past, there were two ways of looking that these using a scope with common channel grounds.
1. You can place the signal and ground for a single channel across the sensor. This prevents you from grounding the scope or using any other channels. This is because the scope common ground would ground out the CKP. The advantage of this method is that the full peak to peak signal amplitude and the correct ground reference through the signal center will be shown on the scope. The disadvantage is that you could not use this hook up to do a CKP/CMP relationship check.
2. You can ground the scope and place a channel signal wire onto one of the CKP wires, choosing the correct one so that the waveform is right side up. The disadvantage is that now the CKP true amplitude will be reduced by about 50% on the screen and the signal will float a bit off ground. The advantage is that now you can deploy other channels. Now you can do a CKP/CMP relationship check.
With channels math, we now have a third option to have the best of both worlds. Examples are below.
The first image shows the CKP with the scope grounded to bat neg, channel A on the right side up leg of the CKP and channel B probing the other leg. Note the rulers at channel ground and the peak to peak voltages.
The second image shows the CKP as it really is with channel A across the sensor. Note how ground is now at the center of the waveform and the peak to peak amplitude is doubled.
The third image shows the first one again with an A-B math channel added. Note how the math channel looks a lot like the single channel capture.
The fourth image is the math channel with the single channel capture as a reference waveform overlayed on top of it.
So, we can now use channels math to see the CKP in its full glory as it really is while keeping the scope referenced to bat neg and still have two more channels to deploy as needed.
Since your CMP is non floating you can simply probe the one wire that has the signal and view it as usual.
The above posted in the Autonerdz Community Forums Picogroup area July 1, 2010.http://www.autonerdz.com/cgi/yabb2/YaBB ... 1278004259