VU01 is a high-quality ventilation unit for use with pyranometers and pyrgeometers. Its purpose is to improve the dependability of the measurement. Measurement accuracy improves because offsets are reduced. Reliability benefits from prevention of dew and frost formation and quick evaporation and sublimation of water and snow. ISO/TR 9901 “Solar Energy – Field Pyranometers – Recommended practice for use” recommends use of ventilators where high accuracy and reliability are required. VU01 is designed, using high-quality materials, in agreement with the recommendations of ISO/TR 9901 and BSRN.

VU01 may be used in combination with Hukseflux’ SR20 secondary standard pyranometers and IR20 and IR20WS research grade pyrgeometers. VU01 provides an airflow over the instrument body and dome and has a 5 W and a 10 W heater on board to heat the air. The VU01 ventilation unit runs on 12 VDC voltage. Ventilation promotes thermal equilibrium between all components of radiometers, and thereby reduces zero offsets. Dew and frost formation is prevented. Additional heating will promote evaporation of water droplets and sublimation of snow. It should be noted that heating in combination with pyranometers will lead to increased thermal offsets, so heating is only recommended if necessary.

Operation

Using VU01 is easy. The footprint of VU01 is small, which prevents accumulation of snow. The ventilator power is relatively high in order to increase the airflow. The ventilator is generally used continuously; the heater is typically controlled by the datalogger. Ventilation is typically used with high accuracy measurement requirements. In such cases the need for a high level of instrument maintenance and dome cleaning still exists; evaporating droplets of water might leave stains on the instrument domes. The bottom of VU01 provides access to the removable dust filter. For more information on VU01 please download the product brochure or ask for the user manual.

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