I have included the image of my measurement setup in the following link. Please have a look.http://www.flickr.com/photos/11573533@N00/6777847083/in/photostream
I have built this set up to measure the Waspmote dynamic current consumption under various operation scenarios. however, it can be used to measure any electronic device's dynamic current consumption as well.
You need to plug in the "battery power in" to the battery power source of your device. The "Battery power out" needs to be plugged to the device to power it. This set up is nothing more that a shunt resistor in series to the ground line that connects the battery to the device. The battery GND side of the shunt resistor is called Vin and goes into the (+) input of the Opamp shown. The opamp simply amplifies Vin based on the ratio of two resistors. I have indicated the gain formula on the figure. The opamp I used is LM324 as it is very straightforward with 5V single rail supply.
The Vout of the Opamp is fed to the ADC input of a simple MCU. I have used the Atmega2560 as that's what I had handy but you can use another one that suits your requirements. You need to make sure that the ADC resolution you are using is high enough to capture the minimum variations you are interested in. In my case, I used a 10-bit ADC with 5V max input that gave me 4.8mV of resolution, which was sufficient for my application. I also used 2 KHz of sampling frequency that did the job.
The MCU simply samples the Vout and outputs it to a serial terminal where I copy the Vout variations and simply plot them all in Excel. It's that simple!
A sample dynamic current measurement I captured using the above methodology is given in the following link. The x-axis is in units of milliseconds and the y-axis shows values in millivolts.http://www.flickr.com/photos/11573533@N00/6777940093/in/photostream
I was able to capture waspmote's peak current consumptions using this same method. I found it to be extremely useful and will be using it again soon in other applications.
I hope you will find this information useful for your application as well. Please let me know how you get on and whether my methodology was helpful.