[vdr] Re: Shutdown frontend for saving power and heat

[Rene Bartsch <ml@bartschnet.de>]

Am Son, 2003-05-11 um 19.17 schrieb Reinhard Walter Buchner:
> Hi,
> 
> > > > It's a two DVB-s card System (one Rev.1.3, the other Rev.2.1) with
> > > > one wire to the LNB. I've measured the total power dissipation of the
> > > > whole box (true-RMS at the AC-Line).
> 
> > P.S.: How did you measure consumption? With a measurement-set for AC
> > displaying Watts or did you calculate from measured AC-Voltage and
> > -current?
> 
> As I have pointed out before, you *CANNOT* "measure"
> the wattage of the DVB card like that. If you have a fluctuation
> of only 10mA on the mains side, your measurement will be
> off by 2.3W already and that doesn't take the accuracy of the
> wattmeter / DMM into account. On the other hand a 2A
> difference on the 3.3V line translates into 6.6W but only
> 28mA mains difference in current.
> 
> There is only *one* way to measure this and that is directly
> at the DVB card using a riser / adapter card. All other ways
> simply mean "Wer mist mißt, mißt einfach mist" (for
> english speakers "junk in? junk out!").
> 
> Sorry. Measurements and conclusions out of the topmost
> method are IMHO totally useless.
> 

Agree. And you forgot to mention the sinus influenced by DC-devices (the
reason why we got PFC in the PSUs).

So Christian Vogt could do his measurements DC-based on the card(s). But
be careful not to fry them! ;o)

Rene



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