In March 2010, the CNR4 replaced the CNR1 and CNR1-L. Like its predecessors, the new CNR4 is a rugged net radiometer from Kipp & Zonen consisting of a pyranometer and pyrgeometer pair that faces upward and a complementary pair that faces downward. Its upper pyrgeometer has a meniscus dome that allows water droplets to easily roll off of it, and increases the field of view to nearly 180° instead of the 150° field of view you get with a flat window.
With the CNR4, each pyranometer and pyrgeometer is individually calibrated for optimal accuracy. The CNR4 also weighs less than its predecessors and contains both an internal thermistor and an internal platinum resistance thermometer (PRT). This radiometer does not include a heater, but the optional CNF4 ventilation and heating unit is available for customers who are concerned about dew or frost forming on the domes. The CNF4 easily attaches to the CNR4 (shown below).