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CVF 4 Ventilation Unit

CVF 4 Ventilation Unit

Quick Overview

The CVF4 Ventilation unit is a low maintenance ventilation unit with a fan and inlet filter that provides a flow of clean air over the dome of a radiometer. The integrated heater allows the air to be warmed when necessary. The fan of the CVF4 runs continuously to reduce dust and dirt settling, to dissipate rain drops and to stabilise the dome temperature. A tacho output from the fan gives two pulses per revolution and allows remote monitoring of the fan operation using a data logger. The CVF4 is designed to be used with Kipp & Zonen CGR4 pyrgeometer and CUV5 total UV radiometer plus the CMP and SMP series pyranometers.


  • Increase the interval between maintenance visits
  • Increase the accuracy of measure data
  • No precipitation or condensation on the sensor
  • Reduce the zero offset of the sensors
  • Frost, snow and ice can be melted
  • The World Meteorological Organisation (WMO) and the Baseline Surface Radiation Network (BSRN) guidelines advise using a ventilator to optimise the performance of radiometers in general.

The CVF 4 Ventilation unit can be used to improve the measurement accuracy of Kipp & Zonen radiometers, pyrgeometers and pyranometers. The ventilation unit generates a constant swirling air flow around the sensor to prevent dust and dirt from settling, to dissipate rain drops and to stabilise the dome temperature. The unit is also fitted with an integrated heater that can be used to keep the air just above ambient temperature.

The CVF4 is suitable for all CG, CGR, CUV CM, CMP and SMP radiometers. However with CGR3, SMP3 and CMP3 the ventilation effect will be less due to the larger opening around the dome. The CVF4 is meant to run continuously but the heater can either be switched on permanently for cold regions or be switched by a data logger or clock to remove dew in the morning and be switched off afterwards. In that case the heater should be operated from about 2 hours before sunrise to an hour after sunrise. This saves power in situations where power is limited such as PV operated sites.


Air temp rise caused by CVF4:

<0.25°C @ 0 Watt (ventilator only)
<1°C @ 5.5 Watt (Heater)
Tacho Output:

5V, 2 pulses per revolution
8800 pulses per minute (nominal)
Power Supply: 12vDC @ 0.9A (with heater)
Power Consumption: 5W, 5.5W with heating
Operational Temp Range: -40 to +70°C
Humidity Range: 0 to 100% non condensing
IP Rating: IP54

Availability: Stock Item