The Kestrel 4200 will automatically calculate cfm, as well as contain mixing ratios that calculate grains per pound of moisture. In addition the 4200 calculates humidity, wet bulb, dewpoint, altitude, pressure, and density altitude. It stores up to 4,000 data points and has data upload capabilities.

Kestrel Pocket Weather Meters, 21 Creek Cir., Boothwyn, PA 19061; 610-447-1555; 610-447-1577 (fax);