flyback voltage

[macross]

I have built a pulse induction metal detector, but since it has some problems i need to use an oscilloscope to figure out whats wrong. But i'm concerned that flyback voltage from the coil might damage my scope, since it's rated only for 300vrms. I have read an article of another PI detector which also included scope images which showed flyback voltages of ~320v... Crazy!
So could a flyback voltage damage my scope?

[commongrounder]

When you start getting up into that voltage range, you should be using a 100x scope probe.  Normally you would us the 10x probes that (I assume) came with the scope.  This gives you, in theory only, 10 times the maximum voltage handling, i.e. 3000 volts max instead of 300volts, but most 10x probes have a much, much lower maximum voltage rating.  Check the documentation that came with the probes.  100x probes divide the voltage by 100 which gives you a very comfortable margin and most 100x probes have a 1kv maximum voltage (again check the documentation).  I use 100x probes for my work on vacuum tube amplifier circuits.
Please be very careful around these voltages, as they can be fatal if contacted.  Best to connect everything with power off and stand back for testing!

[macross]

Checked my probe documentation it says x1 - 150v x10 - 300v so it's a no go.

[commongrounder]

100x probes can be had for reasonable prices from the 'bay.  If you plan to scope out higher voltages very often, they are a good investment for safety of your scope inputs and for you as well.  Best of luck!