Description
The housing design of the CMP 21 is fitted with a screw-in drying cartridge that can simply be removed using a coin. This allows the desiccant to be replaced as required using the convenient refill packets. The CMP 21 also features a passive temperature compensation circuit with a standardised linear function.
The CMP 21 has a 32-junction thermopile sensing element, which features faster response, better linearity and a wider measurement range than the CMP 3 and CMP 6. Additionally, the CMP 21’s are individually optimised for temperature compensation and each sensors includes a separate 10K thermistor, or PT100 sensors to monitor the housing temperature for post-processing compensation adjustments.
The integral bubble level is raised to the top of the housing and can be viewed without removing the redesigned snap-on sun shield, which also covers the connector. The connector with gold-plated contacts allows for easy exchange and re-calibration.
It is the choice for scientific use and in top level solar radiation monitoring networks such as the BSRN (Baseline Surface Radiation Network) or WMO (World Meteorological Organisation).
Diagram

Specification
| Classification to ISO 9060:2018: | Spectrally Flat Class A |
| Sensitivity: | 7 to 14µV/W/m² |
| Expected Output (0-1500W/m²): | 0 to 21mV |
| Response Time (95%): | <5 Seconds |
| Spectral Range (50% Points): | 285 to 2800nm |
| Zero offsets (unventilated) (a) thermal radiation (at 200W/m²): (b) temperature change (5K/h): |
< ±7 W/m² < ±2 W/m² |
| Non-Stability (Change/Year): | <±0.5% |
| Non-Linearity (100 to 1000W/m²): | <±0.2% |
| Direction Response: | <±10W/m² |
| Temperature Response: | <±1% (-20 to +50°C) |
| Field of View: | 180° |
| Detector Type: | Thermopile |
| Operating Range: | -40 to +80°C (0-100%RH) |
