Hi guys. Can someone give me an answer for beginner question please? WHAT If the vehicle has a POSITIVE GROUND, made by positive lead from battery , can we use lab scope as normal or we can't? Do we actually need to swap the ends of testing (probe) leads and make the ground crocodile clip as our testing (probing) point and original testing point as a ground connected to the positive ground. Hope I didn't confused you more than it is for me right now. Would be really appreciated if someone can help with this. Thanks.
To me the lab scope doesn't care. Same as reversing the leads on a negative grounded vehicle. If you reverse the leads, your waveform appears upside down to you. Right off I can't think of a testing situation where the polarity would really matter. Perhaps someone else can though.
Hello guys , thanks for your reply. I understand that the waveform may look upsidedown when leads will swapped, but what about to using a current clamps OR pressure transducer where internal circuit is designed to send signal to scope through middle pin on BNC connector and negative on the ring on BNC? Do we have to consider this? Just asking to prevent fry the scope.Thank you for sharing your wisdom.
Over 40 years since I worked on a car with + earth. Don't try and flip the signal by switching the connections especially on a multichannel scope unless the grounds for each channel are isolated from each other.. With a BNC connector the inner is always the signal (+, - or AC)
The scope dosen't care which polarity the car is, on most scopes (ie not the cheapest Hanteks) the signal can be inverted by the software, with an amp clamp it is even simpler the jaws just need flipped over to turn the current trace the right way up.
Ignition secondary wave forms are normally the conventional way up because coils on +ve ground engines coils are wired the opposite way round.
" We're trying to plug a hole in the universe, what are you doing ?. "
(Walter Bishop Fringe TV show)
