Please make sure that you have the latest firmware.

There is a significant change on firmware v1.4 which makes the cloud sensor algorithm calculation more reliable.

Clouds reflect the infrared radiation of the ground back to earth, The lower the difference in Ground vs Sky temperature, the more the clouds in the sky.  If the difference is high, then this is a sign that the infrared radiation is not reflecting to earth.

Lots of factors affect the actual sky temperature. Your geographical latitude, the season, the ambient temperature, and conditions in the troposphere will shift the sky temperature so a correction model is automatically applied by the Uranus device.

One of the most important factors is the ambient temperature which is taken into consideration by the device and adjusts the actual temperature sky readout. The temperature difference in cold vs hot climates (or winter vs summer) plays a significant role in the calculation and makes this crucial to determine if the sky is clear or has sparse clouds.

Overcast skies tend to differ more between the winter and summer months with those in winter tending to be quite a few degrees colder. This is usually because the cloud base is at or near the same temperature as the ground temperature in the respective season. So, a typical summer cloud base temperature might find itself at 12°C; a winter cloud base temperature at -2°C.

In essence, the temperature gap between clear skies and cloudy skies is not a straightforward relationship. It depends very much on the season and local variation.

Uranus measures the cloud IR temperature and compares it with the ground ambient temperature. The higher the difference (ΔΤ), the less the clouds. Usually, a difference above 30 degrees indicates a clear sky.

The cloud sensing model can be configured/tuned from Unity software by pushing to the Uranus device the temperature difference value in which the sky is clear, in your site.

As noted, the season (winter or summer), your local variation, and other conditions can severely affect this model. Fortunately, it is pretty straightforward and the tuning of the cloud sensing model can output reliable examples between clear, light clouds, sparse clouds and overcast sky.

The default setting is 20. As a start make sure that your default value is set to 20 on the cloud detection slider. (Unity Platform).

This means that a temperature difference of more than 20 degrees is considered as a clear sky! You can experiment with the value based on your local variation and conditions of your site.