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. Prepare the Evaluation Kit (EK) as described in Set up the evaluation kit.
2. Mount a 1 Ω resistor on the footprint for R3.
3. Set the oscilloscope to differential mode or a mode that is similar.
4. Connect the oscilloscope using two probes on pins 1 and 2 of the P5 connector as shown in the following figure.
5. Calculate or plot the instantaneous current from the voltage drop across the 1 Ω resistor by taking the difference of the voltages measured on the two probes.
   The voltage drop is proportional to the current. The 1 Ω resistor causes a 1 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 1× attenuation
• Enable averaging mode to reduce random noise
• Enable high-resolution function if it is available

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