[LAD] [ot] rme fireface: weird balanced output measurements (again)

[Fons Adriaensen]

On Fri, Feb 17, 2012 at 01:34:27PM +0100, Jörn Nettingsmeier wrote:

> hot to ground: 2.00 V
> cold to ground: 1.82 V

Looking up the specs of the FF800 it seems that the outputs are
'servo balanced', which is just another name for what I called
'pseudo floating'. 

With such outputs you should never use hot or cold on its own,
and always use both even if that means shorting one of them
(normally the cold one) to ground if the destination is 
unbalanced. Same as for a transformer isolated output in fact.

Try loading both hot and cold (both at the same time) with
equal low (1 kOhm) resistances to ground. Voltages should be 
more equal in that case. Ideally they would have the same
ratio as the loads, meaning no current runs into ground.

Ciao,

-- 
FA

Vor uns liegt ein weites Tal, die Sonne scheint - ein Glitzerstrahl.