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I'm recording voltage and current waveforms using an oscilloscope. The application is pulsed power.

A problem I am having is the oscilloscope is losing power / turning off when I trigger the system. The oscilloscope is connected to voltage and current probes via coaxial cables. Power is provided to the oscilloscope by a battery-powered-UPS (which is disconnected from mains power during tests).

The oscilloscope can lose power immediately after triggering the system, or a few seconds later. Sometimes it seems to work just fine and I can record the desired waveforms. When the oscilloscope does lose power, it happens both when I measure voltage and current together, and when I measure them individually. When the probes are disconnected and the coaxial cable is lying on the floor, it also picks up a signal.

I think the oscilloscope is being turned off because the signal along the coaxial cables is too strong. I don't want this happen, and am concerned I'm damaging the oscilloscope.

What are some things I can do / need to consider to stop this happening? Even generally, what would cause an oscilloscope to lose power like this, and how would that be rectified?

My background is not electrical engineering so I am a bit lost. Appropriate search terms for me to use would also be helpful, so I can try to do some more self-research.

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  • \$\begingroup\$ What kind of system are you taking measurements of here? \$\endgroup\$ – duskwuff Apr 8 at 0:39
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    \$\begingroup\$ The system is a pulsed power unit. Internal capacitors and closing switches, then the electrical breakdown we want happens between external electrodes. \$\endgroup\$ – Aaron Apr 8 at 1:06
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    \$\begingroup\$ I forgot to mention, when the oscilloscope loses power, the UPS is tripped (it starts beeping, loses power and needs to be reset). During the tests the UPS is running off battery, and is physically unplugged from mains power. So the only connection is has is to the oscilloscope. \$\endgroup\$ – Aaron Apr 8 at 1:12
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    \$\begingroup\$ Questions here need to include full detail - in your case, you're going to have to disclose the entire experimental setup, both schematically and in the physical implementation. \$\endgroup\$ – Chris Stratton Apr 8 at 1:13
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    \$\begingroup\$ Unfortunately, all of the critical detail is missing from your diagram. You are going to need to share information that would actually let someone replicate your experiment, before the issue is going to be apparent. If you aren't willing to do that, then you can't use this site as a resource. \$\endgroup\$ – Chris Stratton Apr 8 at 4:21
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A high power pulse generator is effectively an EMP device. You need to shield both the computer and UPS from the EMP, both electrostatically (e.g. screen Faraday shield) and magnetically (e.g steel or mu-metal enclosure). It would also be useful to shield the input cables, but since at least some part of them must extend outside the enclosure, they should connect only through feed-through ports with a solid common ground to the enclosure. You'll also need to calculate how much energy the cables pick up -- you may need to create some means to bypass common-mode pickup or to route the cables through metal conduit.

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