RS-485 standards mandate that a separate signal ground (Not always the same as Earth ground) wire be used to connect signal grounds at remote nodes so that the common mode of the signal wires stays close to the center voltage of 2.5 volts, or 1/2 of the 5 volts that RS-485 IC's normally use.
Without a common signal ground wire hopping from node to node then ...
You won't be able to make this low qty/yr cheaper than buying direct.
The cost of failure exceeds the savings unless you have done this before. But choosing a transformer 1st tells me otherwise. You always start with detailed specs.
You still have to select many sources and perform DVT to their specs and your requirements with accelerated stress tests. ...
This answer is based on a reading of this specification, which implies 10 nominally 50v fixed outputs.
Vin: 8 V DC from LiPo battery.
Number of isolated outputs: 10
Vout: 50 V, 10 mV ripple max.
Iout: 50 mA per output
As the outputs need to be isolated from each other, you need at least one transformer.
As the input is unregulated, you need a ...
Try putting a small capacitor (units to hundreds of nF) between the primary and secondary ground under your isolated DC/DC converter.
EDIT: okay so I misunderstood your schematic... the ADM2682 apparently supplies its own power for the line interface. But the advice about grounding is generic. It could be a DC/DC in your off-the-shelf 485 dongle, or in the ...
Where's the state of the art of Isolated AC/DC SMPS at today ?
For 5V and less than an amp? Inside the nearest name-brand phone charger. You might want to price out wall-warts from CUI. For small production I'd be tempted to build a wall-wart inside my box, but I suspect that UL and CE would both look askance at such practices.
You didn't mention ...
I wouldn't be concerned too much. In an industrial RS485, usually a shelded cable with two wires (A and B) is used. The shield only sheilds EMI noise and it is connected to the ground.
For fairly long distances it is not recommended to connect two grounds together due to compensating currents that will flow trough the shield.
Since the two transceivers are ...
There's no galvanic isolation in your circuit, so if there is no external source driving the difference between the two grounds, it will settle out to be a significant fraction of the voltage across R1.