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| Differential probe for offline PFC'd PSU |
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| H.O:
Nah, I wouldn't say more (or less) accurate based on attenuation factor alone. Gain accuracy is specified as 2% for both probes. But measuring something like a 3V differential bus signal with a 10:1 probe will produce 300mV input into the scope while with the 50:1 probe it's only 60mV. If both probes generates the same amount of noise then clearly having a 300mV signal is "better" than having a 60mV signal and this why I originally wanted the DP10007. I'll see if I can find some time tonight to run some experiments. |
| nali:
--- Quote from: Faringdon on July 10, 2022, 11:00:01 pm ---Isol transformer https://www.screwfix.com/p/carroll-meynell-3000va-intermittent-isolation-transformer-230v-230v/320hv ...i realsie that the secondary "neutral" of these isol txfmrs is always connected to earth....so in fact i will have to ensure that i take it apart and unscrew that earth connection first. --- End quote --- :palm: Where did you get that notion? We have a couple at work, visually identical though I don't know if they're actually the same. The Earth connection is linked through from the Primary to the Secondary sockets. No connection at all between Earth & the secondary windings. |
| Faringdon:
--- Quote ---The Earth connection is linked through from the Primary to the Secondary sockets. --- End quote --- ......so if powering the scope from the isol txfmr, you can just not connect the earth to the scope. ..in fact, that sounds the cheapest way...just need an ~200W isol txfmr...then scope away and just careful not to touch scope ground whilst powered up. |
| wasedadoc:
I power the PSU being investigated from a £40 UPS. UPS unplugged from AC mains and all other output loads. Also use a cheap 100:1 probe. Scope remains earthed as normal. Still not a recipe for poking about with gay abandon. |
| BrokenYugo:
--- Quote from: Faringdon on July 11, 2022, 02:04:23 pm --- --- Quote ---The Earth connection is linked through from the Primary to the Secondary sockets. --- End quote --- ......so if powering the scope from the isol txfmr, you can just not connect the earth to the scope. ..in fact, that sounds the cheapest way...just need an ~200W isol txfmr...then scope away and just careful not to touch scope ground whilst powered up. --- End quote --- That solves nothing. Do it right before you get yourself killed. |
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