Measure current profile with an oscilloscope

An oscilloscope can be used to measure the average current over a given time interval and capture the current profile.

1. Mount a 10 Ω resistor on the footprint for R64.
2. Set the oscilloscope to differential mode or a mode that is similar.
3. Connect the oscilloscope using two probes on the pins of the P22 connector, as shown in the following figure.
4. Calculate or plot the instantaneous current from the voltage drop across the 10 Ω resistor by taking the difference of the voltages measured on the two probes. The voltage drop is proportional to the current. The 10 Ω resistor causes a 10 mV drop for each 1 mA drawn by the circuit being measured.

The plotted voltage drop can be used to calculate the current at a given point in time. The current can then be averaged or integrated to analyze current and energy consumption over a period.

Figure 1. Current measurement with an oscilloscope

To reduce noise, do the following:

• Use probes with 1x attenuation.
• Enable averaging mode to reduce random noise.
• Enable high-resolution function if available.

Use a minimum of 200 kSa/s (one sample every 5 µs) to get the correct average current measurement.