So, I need to find a way to evaluate battery power consumption of a low power widget that periodically wakes up and does some things. What it does is not just CPU; sometimes it activates a sensor, and the sensor activation can use varying amounts of power. To make things particularly difficult there is a considerable range in current from around 500nA to approaching 2 amps, and various levels in between, depending on a complex state machine. So calculating the power usage in a typical environment and over various parameters (software, temperature, low-battery condition etc) is not trivial.
I have been looking at various SMUs which claim to be able to able to measure and source current over a wide range e.g. Keithley 2400 and Keysight B290xA but despite me wanting to spend money no one at either of these companies seems to know how well these instruments will cope with: a) moderately high dynamic range with transients on the order of a few hundred μs and b) accumulating the energy accurately over some time (several days at a time.) It seems sales engineers are less engineers and more "buy it or go away", or maybe the purchase of just one instrument isn't interesting enough, who knows.
So...question for the SMU / test equipment guys here... Will an instrument like this do what I need? If not, how do I solve this measurement dilemma?
I want to be able to measure energy in mAh*, Wh or Joules. (I would prefer an instrument that could do this automatically, but if I have to average data that's captured, then that's an option.)
Budget is limited - probably less than £4,000 - as I need to convince the boss to spend the money and we've just blown £50k on something else I specified, so I imagine the wallet is going to be tight.
I am aware of the Keysight N6705C, but this seems like wayyy overkill for the job. Besides, the quote with the required module came in around £8k, and the Keysight guy still wouldn't tell me if it would do what I needed, but did offer to loan us one for a 3-day trial. And then stopped replying to his emails.
*yes I know this isn't really energy but it will suffice