The Joulescope autoranging uses a combination of dedicated analog hardware and digitized sample values in the FPGA. The analog hardware is fast but the thresholds are fixed. The FPGA thresholds on the digitized samples are slower, and have a latency of about 4 samples (2 µs). The FPGA thresholds are programmable as of firmware 0.5.0, but they are computed in the Joulescope microcontroller firmware based upon the per-device calibration. I don’t have a quick way to change this.
Are these waveforms in the figures above representative of your full device behavior? Right now, the Joulescope is likely staying in the 1.8 mA range the entire time. If so, then even adjusting these thresholds would just keep Joulescope in the 18 mA range the entire time, which you can already do manually. The downside to using the 18 mA range rather than the 1.8 mA range is reduced resolution (increased noise floor) and increased offset error.
You can also try manually setting the 180 mA range to give you a higher-bandwidth view of your current waveform. The offset error will increase another 10x, but the waveform shape will have 10x bandwidth and resolution is still an acceptable 15 µA. The 180 mA range uses a 0.11 Ω shunt resistor. With 20 µF load capacitance, the system bandwidth (not Joulescope’s measurement bandwidth) is still the limiting factor:
Fbw = 1 / (2 π R C) = 1 / (2 * π * 0.11 Ω * 20 µF) = 72 kHz
Here is the table from the Joulescope User’s Guide:
I need to do a better job explaining expected system bandwidth, not just Joulescope’s measurement bandwidth. In practice, all current ranges but the 10A and 2A ranges are often limited by system bandwidth.
Here is how you can export a smaller snippet from your JLS file:
- Start the Joulescope UI
- Open the JLS file: File → Open
- Navigate to the region of interest
- Place Dual Markers: Right-click on the x-axis (time in seconds), click Annotations → Dual Markers
- Left-click on the left marker, move to the starting location, left-click again to drop.
- Left-click on the right marker, move to the starting location, left-click again to drop.
- Right-click on either the left or right marker, click Export Data.
Note that the JLS file format is currently truncated to a multiple of 0.2 seconds (which will eventually be fixed). The total duration should be either just over 0.2 seconds or just over 0.4 seconds to post accurately to this forum due to the forum file size limit.
Hope this helps!