SDI panel insulation

[samchurchill]

Hi,

 

Hopefully just a quick question which I can’t find an answer to anywhere... am I correct in assuming that, as products like https://www.canford.co.uk/Products/48-5101_COAX-CONNS-10-503-B126-BNC-12G-UHD-Female-panel-75-ohm-double-sided-nickel-inc.15mm-hex-nut exist, multiple BNC SDI connections in a panel should be of the insulated type?

 

Thanks,

 

Sam

[mac.calder]

Only if you need an isolated ground. Generally you don't.

[samchurchill]

Ah, so something like https://cpc.farnell.com/pro-signal/bnc22/bnc-socket-insulated-b-head-75r/dp/CN18186 would be suitable most of the time? Could you give me an example of when I might need an isolated ground? I think I’m right in saying that generally digital systems don’t suffer from the same noise as analog if they’re on different phases (that’s been my experience, but please correct me if I’m wrong!).

[mac.calder]

In general AV etc - nope.

 

In instrumentation - yes. BNC is a pretty common connector to use for probes on oscilloscopes for example - you want to be able to set your own reference ground in that instance and not be tied to chassis/electrical ground.

 

In OB situations - maybe - not sure.

[J Pearce]

Are they all SDI going to the same bit of kit, or are any of them likely to get used for other things like MADI or even composite video? If they're ever likely to get used independently I'd push for not mixing up the coax screen with mains earth, and let the connected kit decide how to bond the screen.

[Stuart91]

Are they all SDI going to the same bit of kit, or are any of them likely to get used for other things like MADI or even composite video? If they're ever likely to get used independently I'd push for not mixing up the coax screen with mains earth, and let the connected kit decide how to bond the screen.

 

So there are potential downsides to having uninsulated connectors all bonded via the panel.

 

Are there any potential downsides to keeping them insulated and independent? Or is it just a case of cost?

[mac.calder]

Cost and availability.

[Brian]

So there are potential downsides to having uninsulated connectors all bonded via the panel.

 

 

Yes. Digital video signals can suffer from earth loops just as much as an analogue audio signal can. Too much voltage on the screen and you might exceed the common-mode voltage range of the input stage of the receiving unit.

[samchurchill]

Thanks all, even though they’ll all be terminated into the same switcher 1m past the panel, I thought it best to be safe than sorry, so went for insulated.