Solar Sensors, Data, and Sunshine Hours - Some Background Information

Over the past months or so I have notice that some myths and misunderstandings have arisen over the solar sensor and what is does and I have found myself repeating stuff, so I felt that a new FAQ might be appropriate to cover what a solar sensor is and what it does or does not do.

This FAQ is to try to clear up some of the misconceptions about solar sensors and how they work in relation to Weather Display. I am not covering the set up within WD as Brian has this covered in another excellent FAQ but will try here to dispel some myths and explain how this works.

Firstly people need to understand that the vast majority of solar sensors available for the hobbyist are not accurate instruments. Those from Davis measure global solar radiation on a horizontal plane and not direct radiation. There are other higher cost stations and accurate stations such as Rainwise, Texas Weather Instruments, Campbell Scientific etc., although I am not familiar with this equipment. This means that the global radiation sensors cover the whole sky from sunrise horizon to sunset horizon (or as much that is visible from their physical position). Sensors which measure direct solar radiation are in the main very expensive and well beyond the finances of the majority of hobby weather enthusiasts. Basically anyone wishing to obtain reasonably accurate solar readings are left with only Davis or other more expensive stations as choices, the errors created by the cheaper types of sensors are such that this does become rather unreliable.

My experience in all of this is with the Davis Solar Sensor but the principles explained here as to how the software works would apply to any sensor which provides readings in W/m