nRF52840 Preview DK v0.9.x

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 Figure 1.
  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, calculate average current over a period, or integrated to calculate the energy used over a period.
Figure 1. Current measurement with 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.


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