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 Evaluation Kit (EK) as described in Preparing the evaluation kit.
- Mount a 1 Ω resistor on the footprint for R3.
- Connect an oscilloscope in differential mode or similar with two probes on pins 1 and 2 of the P5 connector as shown in the following figure.
- 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
Some tips to reduce noise:- Use probes with 1× 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.