[maemo-developers] [maemo-developers] Measuring power consumption of 770

[From: Larry Battraw]

I concur; measuring the voltage and current simultaneously (And
rapidly) is critical.  I've tried these type of measurements before
and it's not nearly as simple as you would think.  A one ohm resistor
is not a good idea-- it will drop too much voltage, causing the device
to shutdown.  Assuming wireless is active, it will be drawing roughly
500 mA, which translates to a .5V voltage drop, leading to the device
seeing 3.2V which will cause issues.  Likewise, 500 mA is only an
average and the peak currents are likely to be much higher.  I would
suggest using a .1 ohm resistor, and to make sure that you measure the
voltage across the resistor at the same points you feed the power
through so you don't end up measuring the voltage drop of the wires as
well.  At .1 ohms, it won't take much to throw the measurements off.

Larry

On 3/15/06, Teemu Nikkilä <tnikkila at cc.hut.fi> wrote:
> On Wednesday, 15. March 2006 13:44, Igor Stoppa wrote:
> > If I'm proposing the battery, there's a reason ...
>
> Yes, this must be the least problematic way.
>
> > and no, i won't go
> > any further, but anyway faking a battery is not the scope of this study,
> > according to my understanding, so using a real one will be just ok.
>
> You just need to measure and record the cell voltage too to get the actual
> power consumption.
>