This type of analysis can also be done using the X-Y mode on most oscilloscopes: Note that this power consumption can’t be reduced: we don’t have the ability to send any commands to the RFM12B until it has started up! As you can see, the current draw quickly rises between 1 and 2V, and then continues to increase sort of linearly. The magenta trace is the current consumption, which turns out to be 0.650 ♚. The yellow trace is VCC, the supply voltage – from 0.3V. This will have a slight effect on measurement accuracy – but no more than 2%, so I’m ok with it. So the idea is to apply a sawtooth signal to the RFM12B, rising from 0 to 3V at the rate of say 10 Hz, and to measure the voltage drop across a 100 Ω resistor at the same time.
Well, time for a test using the power booster described recently: For quite some time, I’ve wanted to know just how much current the RFM12B module draws on power-up.
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