I am working on a battery powered wireless device, and I need to measure current consumption over a long period (days).
I built an µcurrent like device (with specs tailored for the dynamic range I need), and it works, but I don't have an oscilloscope with enough data logging. I am going to buy a new scope, but I don't have the budget for the one I want yet.
I don't know your budget and the period you need to log so maybe this is totally beside the point, but I bought a GW Instek MDO-2204EX scope and was quite impressed with it's logging ability. It has 40M sample memory that can be split into 29K separate segments for high resolution logging of randomly timed events.
On top of this you can download apps to the scope. One of them is a data logging app that has up to 1000 hours logging of images or waveforms direct to a USB stick if 40M samples is not enough. The minimum time interval is 2 seconds.
The app is purely time based, but with the first method you can trig on events like wake up from sleep and store up to 29,000 separate events and measure the power consumption with a quite sofisticated array of math functions. Here's a brief overview of the math functions and apps:
Math functions: Ch1-4, Ref1-4
Measurement Pk-Pk,Max,Min,Amp,High,Low,Mean,CycleMean,RMS,CycleRMS,Area,CycleArea,
ROvShoot,FOvShoot,Freq,Period,Rise,Fall,PosWidth,NegWidth,Dutycycle,
FRR,FRF,FFR,FFF,LRR,LRF,LFR,LFF,Phase,RPRFShoot,FPREShoot,
+Pulses,-Pulses,+Edges,-Edges
Operators +,-,*,/,<,>,<=,>=,==,!=,||,&&,
Functions Intg,Diff,Log,Ln,Exp,Sqrt,Abs,Rad,Deg,Sin,Cos,Tan,Asin,Acos,Atan
App Bode plot: 20-25MHz, log gain & phase 10/15/30/45/90pt/dec, >80dB dynamic range
App Data logging: waveforms, screenshots
App Digital filtering: LP/BP/HP,tracking
App DVM: 3 digit DC/DCrms/ACrms, 5 digit Frequency/Duty-cycle, floating window
App Go-NoGo: compare, violation stop/count, separate entry/exit, tolerance
App Mask: compare, violation stop/count(save), auto/manual
The dynamic range might be an issue so I can see two approaches:
- Measure active periods with the scope segments and sleep with the µCurrent device. Then add the sleep current to the measured active currents.
- Add a logarithmic amplifier to the µCurrent signal to reduce the dynamic range of the signal.
Good luck with your measurements.