Specification of solar radiation sensors
Pyranometers are classified according to the ISO 9060 standard: “Solar energy – Specification and classification of instruments for measuring hemispherical solar and direct solar radiation”. The standard is officially approved by the World Meteorological Organization (WMO). The standard specifies three classes:
Secondary Standard:
Scientific quality and highest accuracy
Applications: Meteorology (BSRN Network); Testing in PV, CPV and CSP
First Class:
Good quality
Applications: Measurements for hydrology networks and greenhouse climate control
Second Class:
Medium quality
Applications: Economic solution for routine measurements in weather stations and field testing
| ISO 9060 PYRANOMETER SPECIFICATIONS | SECONDARY STANDARD | FIRST CLASS | SECOND CLASS |
|---|---|---|---|
| Response time: time to reach 95% responds | < 15 s | < 30 s | < 60 s |
| Zero-offset | |||
| Offset-A: response to 200 W/m² net thermal radiation, ventilated | + 7 W/m² | + 7 W/m² | + 7 W/m² |
| Offset-B: response to 5 K/h change in ambient temperatur | ± 2 W/m² | ± 2 W/m² | ± 2 W/m² |
| Non-stability: % change in responsivity per year | ± 0.8% | ± 1.5% | ± 3% |
| Non-linearity: % deviation from responsivity at 500 W/m² due to change in irradiance from 100 … 1000 W/m² | ± 0.5% | ± 1% | ± 3% |
| Directional response (for beam irradiance): the range of errors caused by assuming that the normal incidence responsivity is valid for all directions when measuring from any direction, a beam radiation whose normal incidence irradiance is 1000 W/m² | ± 10 W/m² | ± 20 W/m² | ± 20 W/m² |
| Spectral selectivity: % deviation of the product of spectral absorbance and transmittance from the corresponding mean, from 0.35 … 1.5 μm | ± 3% | ± 5% | ± 10% |
| Temperature response: % deviation due to change in ambient within an interval of 50 K, (e.g. -10 … +40°C typical) | 2% | 4% | 8% |
| Tilt response: % deviation in responsivity relative to 0 … 90° tilt at 1000 W/m² beam irradiance | ± 0.5% | ± 2% | ± 5% |
| Achievable uncertainty (95% confidence level) | |||
| Hourly totals | 3% | 8% | 20% |
| Daily totals | 2% | 5% | 10% |
