The BNS-06 type device is used to detect sunlight duration (minutes of sunlight). The sensor determines the sunlight by thermal principle, as the black thermal sensor unit warms up under the glass dome. The electronic signal of the thermal sensor is compared with the internal reference temperature sensor by the electronic signal-processor integrated into the sensor's container, and displays the result of the comparison in logical output (shining-not shining). The elemental logical states are accumulated by the BCU-03 data collector. The "i" signed device has RS-485 digital interface. The advantage of thermal sensing instead of other solutions (e.g. optical, etc) is that it serves accurate, reliable values even when high-level clouds are present (won't sign for diffused light, not even when shadow would be seen).