advice on capturing spikes with a Rigol scope

[jahonen]

so if I read that right having two seperate wires may prove better ?

another thought came to mind, isn't back EMF spikes negative ?, how do I set up the trigger in this case, if i'm after a negative peak the scope will run non stop at the power supply will be over the trigger voltage

Set it to trigger on the falling edge, and trigger in "normal" mode, i.e. the scope doesn't sweep until the voltage falls through the trigger point.

Regards,
Janne

[Simon]

that sounds like a plan although I've ben playing at triggering the scope with the 50 Hz sine wave i pick up on my body and it seemed to trigger on both positives and negatives

[Simon]

well i had a fiddle today with a single fan (24 V 8 amps) and did not get very far, at best I caught a oscilation of up to 55 volts but it was all positive, this sucker just does not have back emf. The only thing I can think of it that the power supply colapses the voltage "slowly" as it has a soft on/off button, perhaps I should try putting a switch on it ?