Now my Azure watering system has been running for a few weeks and I can use collected data to undestand how it behaves.
The data on Azure lead to the following graphs:

The big watering bars correspond to manual watering, from this graph I understand several key points:
1 - Humidity level should be maintained between 50 and 300
2 - Cooler temperatures in November have minimized evaporation ...or plants consumption
3 - The humidity variation during a day may be important compared to the interval given before
4 - All humidity sensors seem to follow an identical pattern, but my pots are not identical!!

To know more about humidity Sensors, i will modify the configuration, two sensors will be installed in test tubes, one completely immerged and the other one half immerged .

With this 100% stable configuration and Azure data recording, I expect a clarification on humidity measurement.