In the estimation of evaporation potential of catchment areas, the duration of sunshine in a day is recorded by which instrument?

• Sunshine Recorder:
A sunshine recorder is a meteorological instrument used for recording the amount of sunlight (or amount of sunshine) that a particular location receives throughout the day. Sunshine recorder also known as 'Campbell-Stokes sunshine recorder'. It consists of a glass sphere that focuses sunlight onto a specially designed card or paper

• Radiometer:
A radiometer is an instrument for detecting or measuring radiant energy, or in other words 'A radiometer is an instrument used to measure the intensity (flux) or power of electromagnetic radiation, typically in the form of light or other electromagnetic waves'. The term is applied in particular to devices used to measure infrared radiation. Radiometers are of various types that differ in their method of measurement or detection.