Pyranometer or solarimeter

• measures the electric current generated by a series of thermocouple when exposed to solar radiation
• is calibrated to give the intensity of solar radiation on the basis of voltage recorded
• usually, a milivolt recorder or a digital integrator is connected to obtain, both instantaneous and time records of radiation

Bellani Pyranometer

• gives a measure of total solar radiation
• the glass sphere used to cover the sensor are made of quartz to ensure that all the waves in solar radiation spectrum must reach the sensor

Bimetallic Actinograph

• provides a measure of solar radiation by recording temperature difference between black and white coated bimetallic strips.

Cambell Stoke’s Sunshine Recorder

• the length of the trace burnt on the specially treated card is measured as the duration of bright sunshine
• the intensity of radiation required to burn the card is normally 0.2 to 0.4 cal/cm^2-min, below it no record is obtained

Sunshine Recorder

Three types of cards are used for recording the sunshine duration during different times of the year. They are;

I. Long curved card

ii. Short curved card

iii. Straight card

• Three pairs of flanges are provided on the bowl for inserting the card.
• The central pair is used for straight card for a period of three weeks before and after the days when the day and night lengths are equal (i.e. equinox).
• Long curved card used in summer and short curved card are used in winter.

Spectrobolometer

• is used to measure the quality of solar radiation
• is in fact an arrangement of different instruments that produces color bands in the solar radiation and provide mechanism to measure the energy