Re: DMX optoisolator


"Christian Marg" <christian.marg@xxxxxxxxxxxxxxx> wrote:

> - The signal ground line is also recommended in an RS-485 system to keep
> the common mode voltage that the receiver must accept within the -7 to +12
> volt range
> - Note that the signal ground line should also be connected in the system.
> This connection is necessary to keep the Vcm common mode voltage at the
> receiver within a safe range. The interface circuit may operate without
> the signal ground connection, but may sacrifice reliability and noise
> immunity.

this bit makes perfect sense. Provide a ground not so much as a signal
reference, but as a common reference to keep different bits of equipment
from developing too high a voltage between them.


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