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| [Solved] Newbie Q: What does the derating curve mean exactly for oscill probes? |
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| capt bullshot:
"Derating" usually refers to reduction of some parameter in dependency of other parameter(s). So in this case it's the maximum voltage dependent of frequency (or the other way round). As it says "derating" it means you shall not exceed these parameters, otherwise correct function will not be given. Depending on how far you exceed the parameters, damage to the object or harm to the user can happen. |
| ballsystemlord:
--- Quote from: capt bullshot on August 28, 2022, 08:22:13 am ---"Derating" usually refers to reduction of some parameter in dependency of other parameter(s). So in this case it's the maximum voltage dependent of frequency (or the other way round). As it says "derating" it means you shall not exceed these parameters, otherwise correct function will not be given. Depending on how far you exceed the parameters, damage to the object or harm to the user can happen. --- End quote --- :palm: I understood that much. What I wanted clarification for is that the probes are rated 300V Rms CAT-II (150V Rms CAT-II at 1x). Now everyone will probably understand that as meaning that frequency does not matter so long as you do not exceed the rated voltage. BUT I've actually read one or more papers about how the breakdown voltage of air and enameled wire decreases as frequency increases. So, it probably follows that the same would happen to oscilloscope probes and their leads unless there was some special shielding that prevented such breakdown from occurring. I decided to choose the wisest course of action and ask those who probably know more about this than myself. |
| tautech:
It's very simple really it is. CAT ratings ONLY apply to mains frequencies, 50 or 60Hz. For absolute Max probe ratings apply DC thinking. Everything else derate voltages applied to the probe in relation to the signal frequency as expressly outlined in the derating graph. |
| ballsystemlord:
I think the others made it clear. I was just replying to the gentlemen above because I thought he misunderstood what I was asking and/or thinking. |
| Fungus:
--- Quote from: ballsystemlord on August 28, 2022, 08:40:39 pm ---BUT I've actually read one or more papers about how the breakdown voltage of air and enameled wire decreases as frequency increases. So, it probably follows that the same would happen to oscilloscope probes and their leads unless there was some special shielding that prevented such breakdown from occurring. --- End quote --- It's nothing to do with breakdown. Anything with capacitance will heat up if you charge/discharge it. The more times per second you do it, the hotter it will get. Result: Your probes will melt... ...hopefully before the oscilloscope melts. Oscilloscopes have a derating curve, too. https://www.eevblog.com/forum/testgear/rigol-ds1202z-e-input-voltage-vs-frequency-derating/ |
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