The SMP21 is a Spectrally Flat Class A pyranometer that combines the sensor technology from the CMP21 and has the RS-485 Modbus® interface, analogue output, low maintenance and 5 year warranty (*). The SMP21 has an internal desiccant that will last for at least 10 years, which minimizes maintenance significantly. The interval for dome cleaning can be extended, and the quality of measurements maximized, by fitting SMP21 with the CVF4 ventilation unit. The SMP21 has Modbus® RTU interface, amplified analogue output, improved response time, and individual temperature corrected measurement data. The SMP21 is supplied with individual measured cosine response data. The wide and low power supply range from 5 to 30 VDC makes integration in meteorological and solar energy stations easy. The SMP21 is protected against over voltage, reversed polarity and short circuiting. Thanks to standardized output and connections of every SMP21, exchanging instruments for recalibration is easy. SmartExplorer Windows™ software for data logging, display of data and Modbus® address setting is provided as standard.