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Registered Member #1792
Joined: Fri Oct 31 2008, 08:12PM
Location: University of California
Posts: 527
You could get some TVS diodes: they come in single diodes which protect against positive OR negative spikes, or back-to-back (anti-series?) packages which will protect against both positive AND negative spikes.
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140
Use suitably rated 'scope probes and your intelligence.
ALWAYS ensure the 'scope is "earthed" via the power cable for YOUR protection. (if the 'scope is mains powered)
If the circuit that you are going to probe has voltages greater than a few hundred volts present then use a high voltage probe.
My 'scope probes are almost always set to x10 this is mainly to minimise the load on the circuit under test it also gives some protection for the 'scope inputs.
Over 40 years of 'scoping I've replaced probes many times due to mechanical failures I've never blown a 'scope input.
Read and understand the 'scope probe specifications.
I have never added protection for the 'scope inputs as it would mess-up the frequency response ..e.g. capacitance of tvs/zener.
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
yeah the TVS'es have appalling capacitence if not buffered, i was told by others here on the forum to use spark gap surge asrestors which are very fast and neglagable capacitience, i was going to use 90v breakdown ones on the tip of the probe, before the times 10 division circuit.
Registered Member #195
Joined: Fri Feb 17 2006, 08:27PM
Location: Berkeley, ca.
Posts: 1111
I'm with Sulaiman know what you expect to mesure I bought a 100:1 probe with a 2500 volt rating. If you don't know you could make a basic resistive probe to get a idea of what you may be dealing with. You could invest in a isollation transformer. any 120, 240vac to 120, 240vac transformer will do for basic use. it does not have to be labratory grade. Just find a surplus place or ebay. the bigger the better. If you ground a probe make shure that the place you are grounding it to is connected to the same safty ground as your scope.
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How to protect Oscilloscope inputs from overvoltages?
