# Measure power usage of battery powered device

I'm a software engineer by trade so I'm a bit at a loss. Maybe I don't know the correct words to find what I'm looking for.

I have a Bluetooth Low Energy remote control powered by two AAA batteries. I want to monitor the power usage for the device. I understand how I can put a multimeter between the batteries and the device and measure actual power usage, in milliampere, but I'm more interested in how much power it uses over a span of time. Note that the power usage patterns differ between pairing, standby, when sending a key, etc, which is why I'm much more interested in total power used instead of only the draw at ONE moment in time.

Basically I'm envisioning something like an ampere-counter (electron-counter), instead of an ampere-meter. Which would mean that you read out on the end of the day: 20 mAh used. Does something like this exist?

• This is possible but fairly tricky. However, for a device actuated by a user pushing a button, and having AA batteries, the lifetime is likely to be extremely long unless it is used heavily. How do you plan to set the pattern of usage for a test? Or does this actually have an on/off switch? – Chris Stratton May 8 at 14:47
• Yes, this is one of the main factors. Also I guess it would differ very much between different users how often they'll push buttons on the remote in daily use. But I think is secondary to my question! – MichielB May 8 at 14:49
• Typically what you would do is put a sense resistor in the ground lead, put a capacitor across it, and watch the voltage drop across that on a scope. You can also do it with an MCU/Arduino as the meter. You would be looking for pulses of say 20-30 mA and a lower baseline active and a hard to measure baseline inactive. – Chris Stratton May 8 at 14:52
• Is it integrated current (mAh) you want or integrated power (joules etc.)? Power is voltage x current. Analogue circuit integrators don't work too well when the integration time is more than a few seconds. Maybe think along the lines of a digital integrator. – Andy aka May 8 at 14:54