ASTM E816-05 Calibration of Pyrheliometers by Comparison to Reference Pyrheliometers

Scope:

ASTM E816-05 test method covers the calibration of pyrheliometers by comparison to reference pyrheliometers. It uses only sunshine to apply calibration procedures. The measurements obtained from this method are utilized in quality control, safety assurance, performance evaluation, and research purposes. The specifications and working capabilities of the materials can be determined. This helps specify their applications and enhance their products to meet global standards.

Procedure:

The test apparatus is set up by mounting the self-calibrating absolute cavity pyrheliometer on the sun-tracking mount. The distance between the pyrheliometers should not be greater than 20m. The instruments are then connected to the digital voltmeter. The pyrheliometers are properly adjusted, and the quartz aperture of the secondary pyrheliometer is cleaned. The output voltage and irradiance are measured within a 1-sec interval. The standard deviation of the measured values is determined, and the zero offsets of all pyrheliometers are recorded. 

Specimen Size:

Specimen size should be as per the requirements. In this case, the reference and field pyrheliometers shall be nonselective over a range from 0.3to 4-μm wavelength.

Data:

The calibration factors are determined by applying the equation in which E stands for the irradiance values, and V stands for the voltage signals.