This is a simple holder for a common model of hygrometer found on aliexpress. It keeps the round hygrometer from rolling on a flat surface. The instrument is held at around 30, but you can change the angle in the FreeCAD file provided if you want.
Prints well flat on the frontal face (with the central hole vertical).
The hygrometer is press fit into the hole.
The author marked this model as their own original creation.