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Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3141
TVSs are really useful but for your 'scope probe not directly applicable as low voltage TVS (e.g. 1.5ke range) have large capacitance (e.g. 1nF to 10 nF) A spark gap of the type commonly used for telephone lines etc should be enough to protect a 'scope input and has low capacitance. e.g. <1pF
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3141
The higher the source impedance the less work for the spark gap (peak current/total energy etc.)
I've never used any protection for my 'scopes other than a bit of caution The typical (eBay) x10 'scope probe will probably short internally before your 'scope gets 'threatening' voltage spikes
Registered Member #3883
Joined: Fri May 13 2011, 06:30PM
Location: Norway
Posts: 87
No Sir, long time since I was in school. And I see your point, it was modeled after my other probe and I didn't really give it much thought.
I'm sure I'll make another one before long, once we get the shop back online I will have access to both a manual and a CNC mill. This was more of a boredom-project, just to give me a probe to scope the primary on my ignition coil. I will need a better cable, the inductance is visible even at 1KHz. But it works and will hopefully save the last channel on my scope. If I can get another scope I'll try to fix the one I blew, but that could take time.
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Building a simple 10X probe
