NCAR Airborne Instrumentation Inventory

1. INSTRUMENT IDENTIFICATION

Instrument Designation:
Condensation Nucleus Counter (TSI Model 3760)

Instrument Acronym:
CNC 3760

Instrument Measurements:

a) Trace Gas


b) Cloud Physics/Aerosol
Particle number concentration

c) Radiation/Optical/Electrical


d) Additional Capabilities


Resource Person/Developer:
Name: Cynthia Twohy (also Greg Kok)
Affiliation: ATD/RAF
Phone: (303) 497-1017
Email: twohy@ucar.edu

Principle of Measurement:
Butanol vapor is condensed on small particles; they grow to a size detectable with a simple optical counter

In situ/Remote/Flux Measurement:
In-situ

2. INSTRUMENT APPLICATION

Scientific questions to be answered:
Sources and sinks of particles, including new particle formation, aerosol chemistry, air mass tracer, pollution formation and transport

Field projects in which the instrument has been used:
Multiple since 1988.

Publications describing the instrument, applications and field project results:
Twohy, C.H., 1991: Airborne Condensation Nucleus Counter User's Guide. Technical Note TN-356+EDD, National Center for Atmospheric Research, 21 pp.

3. Instrument Deployment

Altitude:
Surface to 200 mb.

Aircraft Platform:
NCAR C-130, Electra. Others possible.

Inlet Configuration/Location:
Small isokinetic inlet; various locations.

Calibration/Cross Calibration:
Calibration of flow meters and pressure transducers before each project. Counts from data system cross-checked with basic frequency counter.

Operator Requirements:
Minimal once set up and checked. (Power on/off each flight, butanol refill every 50 hours.)

Data Collection:
external

Post-flight Data Validation, Processing, Hours per Flight Hour etc.
Standard in RAF Nimbus processing package.

Physical Characteristics:
Dimensions: 18.5"x23"x8" rack mountable tray Weight: 40 lbs. including pump Power: 110-240 VAC Other:

4. Instrument Performance

Linear Range:
Number: 0 to 20,000 cm-3
Size: >0.013 microns diameter (upper size not characterized)

Response Time:
1/6 s for detection of 10 to 90% increase in concentration.
1-2 s delay in sampling line and instrument.

Detection Limits:
Number: 0.04 cm-3
Size: 0.013 microns diameter

Accuracy:
Varies with concentration, about 6% at 3300 cm-3.

Precision:
0.04 cm-3

Limitations (such as altitude, airspeed, etc.)
Counting efficiency drops at pressures lower than 200 mb. False counts occur in cloud due to droplet shattering.

5. Alternative Techniques

6.Status/Plans

7.Comments