Description (From Recipaedia)
Hygrometer displays humidity of the surrounding area. It is an important tool when planting trees. All trees need a lot of humidity to grow. When a tree is planted an area which is too dry, the sapling will wilt. It is also an electric element that outputs analog signal corresponding to the surrounding humidity.
Crafting
Use 2 iron ingots and 3 malachite chunks to craft one hygrometer.

Notes
This must be an old-fashioned type of hygrometer and actually displays the dryness rather than the humidity. A higher humidity drives the needle to the left and a drier reading moves the needle to the right.
The hygrometer can be connected to an electric circuit and will output an analog signal proportionate to the humidity:

History
- 1.14- Added the Hygrometer. Its uses are to show humidity so trees could grow.
- 1.23- Hygrometers now produce an analog signal.