nRF52840 DK v1.0.0

Using an oscilloscope for current profile measurement

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

Make sure you have prepared the development kit board as described in section Preparing the development kit board.
  1. Mount a 10 Ω resistor on the footprint for R90.
  2. Connect an oscilloscope in differential mode or similar with two probes on the pins of the P22 connector as shown in the figure below.
  3. 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 will be proportional to the current. The 10 Ω resistor will cause 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
nRF52840 DK current measurement with an oscilloscope
Some tips to reduce noise:

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