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Ok im working on a 03 Pontiac grand prix with a 3.8l out of a 2000ish impala. I was checking current waveforms with my amp clamp and my modis edge. Heres where it gets weird. .... i set scope up for the amp clamp, scale, trigger and time base etc. So i scope the number three cylinder and a normal current waveform apears. So i move to the next one cyl 4 and the waveform is now showing in the negative amps (not inverted either) the base line would be at -1 and rise to 0 or 0.2 for the plateau). Checked the next cylinder #6 and different still. Keep in mind i did not change settings on scope and waveform was not inverted. I do t know what to think if my amp clamp is fudged or something else going on. Will post pics and vsm file when i can.
Not sure what device you're actually measuring, because of the mentioned amperage range it might be injectors? When measuring cyl 3 for a second time does it show the "normal" pattern again or is it off then? I am sure you checked it but I'll ask anyhow:
Possibly an interference from another source like iignition coil?
You might want to verify the amp probe on another vehicle or other consumers in this specific vehicle.
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Opps sorry these are for fuel injectors. I have an identical engine in my car so i will test those to see if its the tool. I will have to retake the current measurements as the file did not save for the odd cylinders it did save the good one which i will post later today.
Here are the cylinders 1, 3 and 5 from my car. Apparantly if the amp clamp moves or is rotated the waveform moves up and down the scale. Which i dont think should happen. With the other car i would be holding it and it would be way negative on the scale or would be positive in the scale. As soon as i get to the car again i will get the waveforms again
The cameras capture rate might be catching two images while its taking the pic since scope has a faster refresh rate. With engine off it zeros out to zero no problems.
Hardtopdr2 wrote: Apparantly if the amp clamp moves or is rotated the waveform moves up and down the scale. Which i dont think should happen.
I've never seen a clamp that wasn't affected by wire position within the hole and clamp orientation. The amount of variation yours is showing looks about normal for a large clamp but I'd consider it excessive for a low amp one.
One thing that will mess with clamps is the jaws not properly closing. I always wipe off the jaw mating faces before I zero them.
This is just off if my car the one car i am having issues with was reading way negative after zeroing (-20 to -30 range) then another one was a base line of 12 and going to 18. Which i need to get the snapshots from the problem car again.
Update: the issue was interference from the alternator. when i repositioned the current clamp the readings matched up better. Just frustrating when this happens cause your just not sure.
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