Hukseflux

ACCESSORY

Thermal Sensors

VU01

Ventilation unit for SR20 and SR22 pyranometers and IR20 pyrgeometers
VU01 is a high-quality ventilation unit for use with pyranometers and pyrgeometers. Its purpose is toimprove the dependability of the measurement. Measurement accuracy improves because offsets arereduced. Reliability benefits from mitigation of dew and frost and quick evaporation and sublimation ofwater and snow. ISO/TR 9901 “Solar Energy - Field Pyranometers - Recommended practice for use”
recommends use of ventilators where high accuracy and reliability are required.

Introduction
Ventilation unit VU01 may be used in combination
with Hukseflux’ SR20, SR22 and SR25 Class A
pyranometers and IR20 and IR20WS research
grade pyrgeometers. VU01 provides an airflow
over the instrument body and dome and has twoheaters on board to heat the air. The use ofheating (5 W or 10 W) is optional. The VU01
ventilation unit runs on 12 VDC voltage.

Improved measurement dependability

Figure 1 VU01 ventilation unit with pyranometer SR20.

32Ventilation promotes thermal equilibrium
between all components of radiometers, andthereby reduces zero offsets. Deposition of dew
and frost are mitigated. Additional heating will
promote evaporation of water droplets andsublimation of snow. It should be noted thatheating in combination with pyranometers willlead to increased thermal offsets, so heating isonly recommended if necessary.

Maintenance / cleaning

4Ventilation is typically used with high accuracy
measurement requirements. In such cases theneed for a high level of instrument maintenanceand dome cleaning still exists; evaporating
droplets of water might leave stains on theinstrument domes. The bottom of VU01 provides
access to the removable dust filter.

110Operation
598667Figure 2 Overview of VU01 with SR20:(1) SR20 cable, (2) SR20 connector, (3) SR20 dome,(4) VU01 cover, (5) fixation of cover, (6) levelling feet,(7) VU01 filter retainer, (8) VU01 ventilator, heatersand filter replacement system (below cover), (9) VU01
cable and cable connector, (10) VU01 connector.

Using VU01 is easy. The ventilator is generally
used continuously; the heater is typicallycontrolled by the datalogger. ISO/TR 9901 “SolarEnergy - Field Pyranometers - Recommended
practice for use” recommends use of ventilators
where high accuracy and reliability are required.
More details can be found in paragraph 4.5.2 andannex A. The Baseline Surface Radiation
Network, BSRN, recommends ventilation forradiometers in its BSRN operations manual v2.1.

Copyright by Hukseflux. Version 2312. We reserve the right to change specifications without prior notice
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Hukseflux

Thermal Sensors

VU01 designVU01 is designed, using high-quality materials,
in agreement with the recommendations ofISO/TR 9901 and BSRN. The footprint of VU01 issmall, which prevents accumulation of snow.
The ventilator power is relatively high in order toincrease the airflow. The heaters should beactivated using external relays. A fan status
signal (high / low) may be used by the user tomonitor rotation of the fan.

Suggested use•••

PV system performance monitoring
scientific meteorological observations
extreme climates (tropical / polar)

Choosing the right instrument
Pyranometers are subject to classification inthree classes according to ISO 9060.
Our pyranometer selection guide assists you inchoosing the right instrument. Whatever yourapplication is: Hukseflux offers the highest
accuracy in every class at the most attractive
price level.

VU01 specifications
Compatible instruments

Compliance with standards
Rated operating power

SR20, SR20-D2, SR22,SR25, SR25-D2, IR20,
IR20WS
ISO/TR 9901
BSRN operations manual
7.8 W at 12 VDC(unheated)
10.8 to 13.2 V

Rated operating voltage
range
Rated operating temperature -40 to +70 oC
range
Fan status signal
high / low (optional use)
Heater5 and 10 W at 12 VDC(optional use)
Increase of air temperature 0.5 °C at 0 W heating
1.0 °C at 5 W heating
1.5 °C at 10 W heating
Zero offset a SR20 ventilated 2.5 W/m2 at 0 W heating
Offset SR20 by heating- 2 W/m2 at 5 W heating- 4 W/m2 at 10 W heating
Offset IR20 by heating
0 W/m2 at 5 W heating
0 W/m2 at 10 W heating
Cable resistance
0.3 Ω/m (2 x 0.15 Ω/m)Voltage drop at 10 W
0.12 V/mheating power
Footprint diameter
0.17 mStandard cable length
5 m (see options)

Options124••

longer cable, in multiples of 5 metres(please note the voltage drop of cabling)pack of 5 filters (VU01F)

See also••Ø 165

SR20, SR20-D2 and SR22 pyranometer
IR20 and IR20WS research grade pyrgeometer

About Hukseflux

140

Ø5Hukseflux is the leading expert in measurementof energy transfer. We design and manufacture
sensors and measuring systems that support theenergy transition. We are market leaders in solar
radiation- and heat flux measurement.
Customers are served through the main office in
the Netherlands, and locally owned
representations in the USA, Brazil, India, China,
Southeast Asia and Japan.

Interested in this product?
E-mail us at: info@hukseflux.com

Figure 3 VU01 dimensions in x 10-3 m.
Copyright by Hukseflux. Version 2312. We reserve the right to change specifications without prior notice
Page 2/2. For Hukseflux Thermal Sensors go to www.hukseflux.com or e-mail us: info@hukseflux.com