nRF9161 DK v0.9.1

Measuring current profile with an oscilloscope

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

Before you start, make sure you have prepared the Development Kit (DK) as described in Preparing the DK for current measurements.
Complete the following steps to measure the current profile of the nRF9161 DK:
  1. Solder a 0.5 Ω resistor to R97.
  2. Set the oscilloscope to differential mode or to a mode that is similar.
  3. Connect the oscilloscope using two probes on the pins of the P22 connector.
  4. Calculate or plot the instantaneous current from the voltage drop across the 0.5 Ω resistor by taking the difference of the voltages measured on the two probes.
    The voltage drop is proportional to the current.
  5. Measure the voltage drop over the 0.5 Ω resistor to get the current power profile.
    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
Measuring nRF91 SiP current using an oscilloscope
To reduce noise, do the following: A minimum of one sample every 5 µs is needed to accurately measure the average current.