I'm building a simple circuit with an Arduino Nano board, which will read signals from a Hall sensor and periodically send pulses to a small 5V solenoid. I'll drive it from 6xAA batteries in series, producing 7.2V. The on-time of the solenoid will be very short, and with a small duty cycle that will vary quite a bit (say 1% to 10%). I find here that the solenoid consumes 240mA at 5V if always on, and I guess the board and other bits-n-pieces would add another 50mA?
So, I'd like to be able to measure the current consumption over a set time period, such as a minute or five minutes - with an end goal of reducing the ongoing consumption (I'd like to use 6xAAA batteries, but AAs may be necessary, depending on how low I can push the current draw). However, with the current varying wildly over time, it is hard to get a static readout from my digital ammeter (it takes a good few seconds to settle) and they generally will change frequently (<0.1 sec).
A bit of research shows that I need an integrated ammeter, i.e. an ammeter that integrates over time as here. This question here is interesting, but answers recommend building such a device with an Arduino! I wonder, can such a thing be purchased inexpensively, ready-made?