Mohamed Ismail Bari wrote:

> May be I need to rephrase my second question.- Here is the scenario - 
> 
> I have a device that consumes 150mA when active and 500uA during sleep.
> The sleep/activity happens quite fast and periodic. The current puleses
> overshoots to about 300mA when the device activates.  I want to get a
> good estimate on the power consumption accounting the current
> overshoots. Is there a way for doing it?

The "proper" way to do it is to integrate over the current. 

One quick and dirty form of doing that is to get a typical current form on
a scope (if it is repetitive, this shouldn't be that difficult) and figure
out the area under the curve. It is proportional to the power consumption
(assuming the voltage is constant). This also tells you quickly whether the
300 mA spikes are relevant: if they are relatively short ("needle" shaped)
pulses, the area is small and possibly negligible.

Another form of doing that is to drive the unit from a large enough
capacitor, through a voltage controller that has a known consumption. The
voltage change at the capacitor is proportional to the integral over the
current taken out of it. So you get that, subtract the consumption of the
regulator, and get your device's consumption. 

Gerhard

-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist