optris PI LightWeight kit Operator's Manual page 43

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The USB 3.0 drive should feature a writing speed of at least 10 MByte/ s for PI4xx
(27Hz) and 25 MByte/ s for PI4xx (80Hz)/ PI640 (32Hz). The internal SD card can only
be used for recordings with a PI4xx (27Hz).
USB 2.0 drives are supported for copying data, not for recording data.
The recording box is optimized to work with USB drives with FAT32 file system.
Reassure the stick is formatted with FAT32 file system.
USB drives larger than 32 GB cannot be formatted with Windows OS, but with extra
tools like "HP USB Disk Storage Format
Tool".