Ground-based Counterflow Virtual Impactor Inlet System (GCVI)

Model 1205


The Brechtel Model 1205 GCVI is the ideal virtual impactor tool for probing the detailed properties of actual cloud condensation nuclei (CCN) inside real clouds. The GCVI was developed for long-term, unattended deployments at mountain and other sites with accessible clouds so researchers could explore aerosol-cloud interactions with the ease of ground operation. Significant anti-icing experience from decade-long aircraft inlet development was applied to the GCVI to ensure the automated wind tunnel lid would open and close reliably under most sampling conditions. With on-line cloud, rain and snow detection, the built-in software will automatically turn your system on when cloud is detected and off when the clouds disappear.

  • Peer-reviewed and characterized CVI Inlet
  • Droplet cut size diameters between 7 and 15 microns
  • 15 lpm total instrument sample flow
  • Fully automated for long-term operation
  • Laminar flow element measures sample flow and automatically adjusts to changing instrument flows
  • Counter flow rate adjustable between 1 and 10 lpm to vary droplet cut size in real-time
  • Automatic power on/off with easy-to-use software
  • Wind tunnel lid closes automatically
  • Integrated rain/snow sensor
  • Tower mountable
  • Integrated anti-icing systems
  • Removable porous tube tip assembly


  • Fully automated, hands-off operation
  • Wind tunnel tested, field validated and peer-reviewed
  • Designed for long-term, unattended deployment
  • Easy cleaning of tip assembly
  • Weather-proof rugged design
  • Easy to vary droplet cut size in real-time
  • Easy to use control software

Technical Specs

GCVI Tech Specs

parameter value type
Droplet diameter cut size range 7-15 μm
Add flow rate range to tip 16-25 lpm
Add flow temperature range 20-45° C
Range of counterflow air flow rate 1-10 lpm
Constant air sample flow rate 15 lpm
Total air sample flow available to instruments 15 lpm
Compressor, vacuum pump and blower power (max) 2000 watts @ 230 VAC
Anti-icing power (max) 1160 watts @ 28 VDC
Other power (external laptop) 50 watts @ 115 VAC
Weather-proof enclosure size 25"W x 50"H x 34"D
Weather-proof electronics enclosure weight 220 lb/99.8 kg
Total system weight 290 lb/131.5 kg
Wind tunnel inlet height (tower mounted) 2 to 10 meters
Wind tunnel flow rate 750-1,500 lpm
Wind tunnel throat velocity range 50-100 m/sec
System footprint size 2x2 meters
Operating temperature range -20-35°C
Operating pressure range 500-1,000 mb (abs)

Copyright ©2017 All specifications are subject to change without notice. BMI assumes no responsibility for inaccuracies in this document or for any obligation to update information in this document. BMI reserves the right to change, modify, transfer or otherwise revise this publication without prior notice.

*Some products may be shown with optional accessories, which are sold separately. Items shown may not be to scale.

Applications and Solutions

  • Aerosol-cloud interactions
  • Cloud condensation nucleus studies
  • Cloud microphysics and radiation studies
  • Pollution impacts on clouds
  • Visibility impacts of fogs
  • CCN and precipitation feedbacks
  • Global climate model CCN datasets


The GCVI built-in control software allows you to operate and configure the system from just the electronics chassis, no external computer is required. You can configure the “cloudiness” visibility and RH thresholds the software uses to automatically turn on AC power to the pumping system and control electronics so sampling begins when cloud is detected, even if you’re not there! The front panel displays of the GCVI and CVI chassis’ provide real-time displays of current parameter values, including wind tunnel speed, wind tunnel anti-ice system temperatures, add flow, total sample flow, and counter flow. You can quickly change the add flow to adjust the droplet cut size and system configuration to suit your sampling needs. Operating pressure and various temperatures are monitored to maintain proper flow and anti-icing system control.

The same on-board software also allows easy access to default system settings so you can customize the performance to your needs. Data can be saved locally to an SD Card accessible through the front of the chassis and/or data may be exported in real-time to an external computer for display and storage. Finally, checking and changing calibrations is a snap with the configuration and calibration tools – all calibration coefficients are accessible for easy update after new calibrations are performed.

Graphical user interface (GUI) software is provided for the user to visualize timeline plots of flow rates, droplet cut size, system temperatures and other parameters. The GUI program runs on a user-provided PC running Windows 7 or later software and with at least two free USB ports. Through the GUI, you also have easy access to default system settings so you can customize the performance. The GCVI inlet runs fine without the GUI program, so you don’t need an external PC to operate the system.

What’s Included

The Model 1205 GCVI inlet comes with the following items:

  • One external CVI inlet sampling probe assembly with drying and anti-icing
  • Compact, anti-iced wind tunnel to accelerate droplets, integrated with CVI inlet probe and mounting system
  • Weather-proof container for control electronics, pumps, blower
  • An inlet manifold for instrument sampling
  • Compressor, vacuum pump and wind tunnel blower to provide all required air flows
  • Integrated rain/snow sensor to shut off wind tunnel automatically
  • Integrated Visibility and RH sensors to detect presence of cloud
  • Wire reinforced system interconnect tubing
  • Pitot Static tube and interconnect tubing
  • Crossover communications cable
  • External DC power supply
  • Graphical user interface software
  • Operator manual

Note: It is the customer’s responsibility to physically mount the GCVI inlet to their tower or other platform.


The following optional accessories are available:

GCVI Accessories

Part Number Description
GCVI-I Automated 3-way valve chassis
GCVI-PC Computer with 1205 GCVI control software
GCVI-Kit Maintenance Kit for 1205 GCVI

Related Products
  • We have deployed a new Ground-CVI from Brechtel for the first time during the Cloud and Aerosol Experiment Åre (CEASAR) from July to October 2014. The experiment took place at Mt. Åreskutan at 1200 MSL within the famous Swedish ski resort Åre close to the border with Norway. The project focused on aerosol-cloud interactions and contrasting clean marine air masses with air influenced by terrestrial boreal forest biogenic emissions and anthropogenically influenced European air masses. Special attention is on partitioning of absorbing aerosol between aerosol and clouds and aerosol removal processes. The experiment is a collaboration between ITM, the Finnish Meteorological Institute and the Paul Scherrer Institute in Switzerland. During the experiment we have collected several hundred hours of aerosol and cloud microphysical data including cloud residual (CCN) properties from the GCVI.

    Radovan Krejci Department of Applied Environmental Science (ITM), Atmospheric Science Unit
    Stockholm University

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