2 ms·

Ethernet is transformer-isolated [1]. If you just need to break a DC ground loop, a CAT-5 connection will do it. If you look at the Tripp-Lite's installation m

• mindslight 13y ago
  Yes, but RJ45 and cat5 don't necessarily imply Ethernet.. DC losses on their own would be high enough to warrant that remote power supply.
  • ISL 13y ago
    Agreed. In the absence of a solution like the 30m 3.Optical, we're desperate enough to try it. We have a working solution using daisy-chained repeaters (for distance) landing in a powered hub, but it's hardly elegant. People make nifty USB-->WiFi interconnects too, but the one we tried can't handle full-bandwidth usage of USB 2.0. It was a sad day when the opto-isolating ADI development board arrived and we discovered, to our chagrin, that Full Speed != High Speed. We were so stoked to have finally found it.
    • mindslight 13y ago
      Those terms ("high" vs "full") are especially tricky somehow. Perhaps that ADI chip I mentioned was the same one, and they tricked me as well. At least I was just researching to determine how bad I would want an Ethernet port if I got a PC scope. (I determined the answer was "pretty bad") I don't know why bona fide high-speed isolators are not a common thing. Maybe 12Mbit ends up being sufficient for 98% of cases? It seems like the only way is to find a type of product for which they can't cheat, like those optical 3.0 cables or an actual GigE->USB protocol converter. Then again Tripp-Lite is a big name, and you really would want some isolation for a 300ft run. Good luck!
      • mindslight 13y ago
        Answering my own question, I ran across an EEVblog post where someone pointed out the problem is the bidirectional data line. OFC that's why you can't just feed them into a GBIC etc. USB 3 has two unidirectional pairs, and so should be easier to isolate. However, don't get your hopes up for those 3.optical cables to do what you'd like either. USB3 actually just implements 480/12/1.5 by having a parallel USB2 bus the whole way. There is no conversion between the two, which also means you can't actually aggregate 480mbit devices with a USB3 hub the way you'd hope. So who knows if Corning has actually created a full implementation or also just punted.
        • deleted 13y ago
          [deleted]
        • ISL 13y ago
          Corning's specs state "Compatible with USB 3.0 and USB 2.0 devices", so I'm still an optimist. We tried to get one early from them, and nearly did, but ultimately couldn't. At $100, I'm sure we'll be trying it out when they're available. Our applications already function well without isolation [1,2], but I'd love to know for certain that the last little bit of ADC noise we see is intrinsic to our readout system and not a little bit of hash on ground. [1] http://arxiv.org/abs/1309.4828 http://arxiv.org/abs/1309.4828 [2] http://arxiv.org/abs/1401.4412 http://arxiv.org/abs/1401.4412
          • cnvogel 13y ago
            Isolating mains-powered devices sometimes is tricky, for example in one device of [1] we resorted to specially wound transformers with increased spacing to minimize capacitive coupling to mains/ground, accepting the resulting higher losses in the low-voltage power-supplies. If you want to research if "ground loops" are indeed of concern, try to inject them artificially (split up protective earth, feed in current from a function generator) and check the influence on your measurement, then you can quantify the "ground loop rejection ratio" of your setup. This will also tell you which frequencies are most susceptible to disturbance in your specific setup. In your paper, you seem to only have a CCD line camera taking the data, most likely it will be easier to cut open the grounding here, mount it using plastic screws and spacers, if not already done. {EDIT:} ...or not feasible because of the heatsinking... [1] http://arxiv.org/abs/1302.6092 http://arxiv.org/abs/1302.6092