I want to measure power consumption and calculate the mAH value to know how much time would my battery can run the circuit. I only got a multimeter and DC power supply.(Im not sure if this is enough to measure)

My project has a temp sensor and measures it every 15 mins. It's going to deep sleep mode and wakes up again to measure.

So how to measure the mAH for this circiut?

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    Depending on the model in question, the Arduino can be horribly inefficient. You are better off using the IC without all the funky stuff around. I recommend you to read Nick Gammons posts on power saving and power budget computation. Most Time you can estimate the power consumption from the datasheets and the up-time. – Kwasmich Jan 25 '19 at 10:14
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    Can you measure the duration of the measurement while waking up? – AltAir Jan 25 '19 at 11:24
  • A good answer to your question (as asked) has been offered. But maybe there's unasked question: "How can I get the maximum run time"? For that, we'd need to know what board you're using. Uno, f/ex, uses a lossy power supply that is on all the time, even during sleep, so sleeping won't help much. If you build a board with an efficient power supply, or use an off-board, efficient power supply that completely bypasses the Uno's(?) on-board one, you can do very much better. If you add more of those details, we could help you more. – JRobert Jan 25 '19 at 12:51

I suggest using a second Arduino to make yourself an "Energy Meter".

Get a very small power resistor (0.1 Ohm) and power your project through it.

Second Arduino will measure voltage drop on it and that way you can get the current that goes through it using Ohms law. You can also measure the battery/power supply voltage. Knowing those two values and micros each loop you can calculate actual hourly power consumption of the device.

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Use the multimeter to measure the current. Put it in mA current mode, and wire it in series from the DC power supply + to the Arduino positive connection. With an Uno, readings will likly be in the 10s of mA all the time, and maybe a little higher when not in deep sleep mode. This assumes you are not powering the Uno from the USB port.

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