Tutorial: particle size statistics in the GUI

This tutorial shows how to measure the particle size distribution of powders in the GUI. How the statistics are computed is described in Particle size statistics.

Step 1 - Acquire

In the Acquisition tab, choose the Measurement:

  • Particle sizes only: particle size statistics, without EDS.

  • EDS + particle sizes: EDS compositional analysis, then particle size statistics on the same samples. The particles in the frames searched by EDS count towards the target, so only the missing frames are acquired.

  • EDS composition: EDS only.

In Particle size statistics, set the diameter range of the particles to measure (min/max particle diameter), the particles per size band, and the particle segmentation model (see Step 3). Then start the acquisition as in Tutorial: EDS compositional analysis for phase identification in the GUI.

Step 2 - View the statistics

In the Analysis tab, select the sample and open Particle sizes. Samples without EDS spectra open directly on it.

  • This sample: the frames with the particles found (see Step 4), then the size distribution and its statistics. What each statistic means: Reported statistics.

  • Compare samples: the distributions of several samples of the folder, with Export CSV.

  • Compare segmentations: the results of this sample (see Step 3).

Step 3 - Segment again with another model

Every frame image is saved, so the frames can be segmented again: in the Segment again section, choose the model and click Segment again. Each segmentation gives its own result, kept next to the others: choose one in the results menu and click Set as active to use it by default.

Models:

  • threshold_bright (default): fast; set the threshold (8-bit brightness of the particles). Touching particles are measured as one.

  • SAM2 and microSAM: segment each particle on its own, also when touching (~30 s per frame for SAM2 on a CPU). They are optional: until installed they are listed as not installed, and selecting one shows how to install it. Install them in your AutoEMX environment, then restart the GUI:

    pip install "autoemx[segmentation]"                       # SAM2
python -m autoemx.utils.install_segmentation micro-sam    # microSAM

    For microSAM, ignore pip’s warnings that micro-sam requires PyQt6, segment-anything-py and trackastra: they are left out on purpose.

options (optional) changes model settings, e.g. {"pred_iou_thresh": 0.7} for SAM2 to find more particles.

Step 4 - Leave out frames and particles

Leave out what was wrongly segmented, e.g. two particles measured as one, or a frame out of focus. In This sample, choose the result in the results menu: the Frames browser, above the size distribution, shows each frame with the outlines of the particles it found: counted (green), left out (red), or not counted because they touch the frame edge or are outside the size range (amber, dashed). Click the dot at the centre of a particle to leave it out (click again to count it), or tick Leave this frame out, then click Recalculate and save. The statistics of that result are recalculated without them, with the same corrections, and saved as a new result made the active one; the earlier ones are kept.