A pyranometer comprising: a dome enclosing a cavity ; at least one light emitting source arranged such that light exterior to the dome does not directly impinge on the at least one light emitting source ; a diffusor ; a solar radiation sensor being arranged to detect light exterior to the dome at least partly impinging on the solar radiation sensor through the diffusor , wherein the at least one light emitting source is configured to emit light substantially directed to a portion of the diffusor , and wherein the diffusor is configured to diffuse the light emitted from the at least one light emitting source on an inner surface of the dome ; and one or more first light detecting sensors arranged in the cavity and configured to measure an intensity of the light reflected from the dome and impinging on the one or more first light detecting sensors , further comprising: a pyranometer housing comprising a chamber , wherein the least one light emitting source is located in the chamber , and wherein the chamber contains the solar radiation sensor , at least one partition wall arranged to at least partially partition the chamber from the cavity such that the light exterior to the dome does not directly impinge on the at least one light emitting source being arranged in the chamber ; wherein the partition wall comprises a through opening , and wherein the diffusor is arranged in the through opening of the partition wall . a dome enclosing a cavity ; at least one light emitting source arranged such that light exterior to the dome does not directly impinge on the at least one light emitting source ; a diffusor ; a solar radiation sensor being arranged to detect light exterior to the dome at least partly impinging on the solar radiation sensor through the diffusor , wherein the at least one light emitting source is configured to emit light substantially directed to a portion of the diffusor , and wherein the diffusor is configured to diffuse the light emitted from the at least one light emitting source on an inner surface of the dome ; and one or more first light detecting sensors arranged in the cavity and configured to measure an intensity of the light reflected from the dome and impinging on the one or more first light detecting sensors , further comprising: a pyranometer housing comprising a chamber , wherein the least one light emitting source is located in the chamber , and wherein the chamber contains the solar radiation sensor , at least one partition wall arranged to at least partially partition the chamber from the cavity such that the light exterior to the dome does not directly impinge on the at least one light emitting source being arranged in the chamber ; wherein the partition wall comprises a through opening , and wherein the diffusor is arranged in the through opening of the partition wall . a pyranometer housing comprising a chamber , wherein the least one light emitting source is located in the chamber , and wherein the chamber contains the solar radiation sensor , at least one partition wall arranged to at least partially partition the chamber from the cavity such that the light exterior to the dome does not directly impinge on the at least one light emitting source being arranged in the chamber ; wherein the partition wall comprises a through opening , and wherein the diffusor is arranged in the through opening of the partition wall . <EOS>