The SR20-D2, manufactured by Hukseflux Thermal Sensors, is an ISO 9060:2018 spectrally flat Class A (secondary standard) digital pyranometer that measures solar short-wave radiation in a full hemisphere of the sky. It connects directly to a Campbell Scientific data logger and is designed for Modbus RTU applications that require high measurement accuracy in demanding applications such as scientific meteorological observation networks and utility scale solar-energy-power production sites.
| Sensor | HIgh-quality blackened thermopile protected by two glass domes |
| Measurement Description | Monitors solar radiation for the full solar spectrum range |
| ISO Classification | Spectrally flat Class A (secondary standard) pyranometer (ISO 9060:2018 ) |
| WMO Performance Level | High-quality pyranometer |
| Response Time | 4.5 s |
| Zero Offset A |
5 W/m2 (unventilated), 2.5 W/m2 (ventilated) (response to 200 W/m2 net thermal radiation) |
| Zero Offset B | ≤ ± 2 W/m2 (response to 5 K/h change in ambient temperature) |
| Non-Stability | ≤ ± 0.5% change per year |
| Non-Linearity | ≤ ± 0.2% (100 to 1000 W/m2) |
| Directional Response | < ± 10 W/m2 |
| Spectral Selectivity | < ± 3% (0.35 to 1.5 x 10-6 m) |
| Temperature Response | < ± 0.4% (-30° to +50°C) |
| Tilt Response | < ± 0.2% (0 to 90° at 1000 W/m2) |
| Heater | No heater available |
| Steady-state Zero Offset |
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| Calibration Uncertainty | < 1.2% (k=2) |
| Level Accuracy | < 0.1° (bubble entirely in ring) |
| Operating Temperature Range | -40° to +80°C |
| Field of View (FOV) | 180° |
| Measurement Range | -400 to 4000 W/m2 |
| Spectral Range | 285 to 3000 x 10-9 m (20% transmission points) |
| Sensitivity | Digital output |
| Output Definition | Running average over 4 measurements (refreshed every 0.1 s) |