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Embedded Systems Architecture by Daniele Lacamera

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Measuring power

The current in use by the target can be measured at any time by connecting an ammeter in series with the device. This mechanism, however, does not show all the oscillations of the values during a time interval, which is why it is often useful to sample the values of the parasitic voltage at the ends of a shunt resistor, using an oscilloscope.

A shunt resistor is placed in series with the target device, on either side of the power source. Its typical value is relatively small, in the range of a few ohms, to ensure that the parasit voltage stays low, but is still measurable by the oscilloscope:

Measuring current using an oscilloscope ...

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