[time-nuts] Frequency counter recommendation

Javier Herrero jherrero at hvsistemas.es
Sun Dec 19 14:04:37 UTC 2010


El 19/12/2010 12:34, Magnus Danielson escribió:
>
> Need to look at it. But essentially, during normal operation common 
> mode isolation isn't all that hard. The problem is that during failure 
> mode can what should be a common mode voltage and current become 
> diffrential mode, which jumps straight through the transformers as a 
> transient and that will burn the receiver anyway...
>
Usually I'm worried with common mode isolation, for noise and EMC 
issues, more than for protection. The kind of equipment where I've used 
it are used in a quite controlled environment (if there is a 
high-voltage transient there, and if it toast the satellite instrument, 
any damage in my equipment would be a lot lot lot less important... 
almost futile :) )
> I've seen people burn their Ethernet port by hooking in an ISDN line 
> to the wrong connector.
>
I can imagine :)
> A wrapped solution like the ADUM1200 puts more stuff between the 
> transformer and actual receiver... so maybe you save the receiver, but 
> you might toast the isolator.
>
Since usually the receiver circuit is also ahead the isolator (for 
example RS422 to TTL, then isolator), it would also be toasted... 
perhaps protecting the isolator :)
> For an optical isolation you might toast the transmitter, but that's 
> about it. Probably that would be the least of your problems when it 
> occurs.
>
Same thing...
> Cheers,
> Magnus
Regards,

Javier
>
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-- 
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Javier Herrero                            EMAIL: jherrero at hvsistemas.com
Chief Technology Officer
HV Sistemas S.L.                          PHONE:         +34 949 336 806
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