Aircraft-based Counterflow Virtual Impactor Inlet System (CVI)

Model 1204


The Brechtel Model 1204 CVI is a virtual impactor inlet ideal for probing the detailed properties of actual CCN inside real clouds. The CVI was developed for aircraft deployment so researchers could explore aerosol-cloud interactions across a broad spectrum of cloud types and under different air mass source region conditions. Extensively wind-tunnel tested to characterize size-dependent transmission efficiencies, the CVI inlet has been successfully deployed in multiple field campaigns where excellent agreement was found between wing-mounted cloud probes and instruments sampling the CCN from the CVI.

Significant anti-icing experience from over ten years of aircraft isokinetic and virtual impactor inlet development was applied to the CVI to ensure the system continued operation under most icing conditions.

  • Controllable droplet cut size (7 to 15 microns)
  • Easy to remove tip for cleaning and replacement
  • 15 lpm of instrument sample flow
  • 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
  • Heated Add Flow to evaporate cloud droplets
  • Anti-icing system
  • Optional kit for Ground-based operation available


  • Fully automated, hands-off operation
  • Wind tunnel tested, field validated and peer-reviewed
  • Designed for long-term, unattended deployment
  • Custom mounting solutions available
  • Easy to vary droplet cut size in real-time
  • Easy to use control software

Technical Specs

Aircraft-based Counterflow Virtual Impactor Inlet System (CVI) Tech Specs

parameter value
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 power (max) 650 watts @ 230 VAC
Anti-icing power (max) 725 watts @ 28 VDC
Operating temperature range -20-35°C
Operating pressure range 200-1,000 mb (abs)
Rack mountable electronics chassis size 17 x 7 x 12 in/43.2 x 17.8 x 30.5 cm
Electronics chassis weight 20 lb/9 kg
Total system weight 100 lb/45.4 kg

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.


  • Cloud condensation nucleus studies
  • Cloud microphysics & radiation studies
  • Pollution impacts on clouds
  • Visibility impacts of fogs
  • CCN & precipitation feedbacks
  • Global climate model CCN datasets

What’s Included

The Model 1204 CVI inlet comes with the following items:

  • External probe assembly with de-icing system, aerodynamic shroud and mounting plate
  • Rack-mount electronics chassis with control software
  • Self-regenerating compressed dry air supply system and vacuum pump
  • Automatic air flow and temperature controls
  • Graphical user interface software
  • Operator’s Manual

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


The CVI built-in control software allows you to operate and configure the system from just the electronics chassis, no external computer is required. The front panel display of the chassis provides real-time displays of current parameter values, including Add Flow, Total Sample Flow, Counter Flow and True Airspeed. 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. Key control parameters like True Air Speed and Ambient Temperature can be imported via serial communications if your sampling setup already has these sensors deployed. 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 one free USB port. Through the GUI, you also have easy access to default system settings so you can customize the performance. The CVI inlet runs fine without the GUI program, so you don’t need an external PC to operate the system if that proves difficult in your application.


The following optional accessories are available:

CVI accessories list

Part Number Description
CVI-Kit Maintenance Kit for 1204 CVI

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