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 parasite voltage stays low, but is still measurable by the oscilloscope:
Figure 8.1 – Measuring the current using an oscilloscope to sample the voltage applied to the shunt resistor
Due to the properties of a series circuit, the current running through the shunt is the same as the one used by the target system, so the voltage on the ends of the shunt resistor varies accordingly.
Development boards
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