Ion Anemometer
Abstract
An ion anemometer is described that is designed to measure one vector component of air velocity in the range from 0 to 120 cm/sec. The instrument's electrical output signal is a measure of the magnitude of the projection of the instantaneous wind vector onto the instrument's single axis of sensitivity. Ganging of more than one device permits the determination of two or three vectors components of the wind velocity. The instrument employs a radioactive source of alpha particles to ionize the air molecules in a small region between two oppositely charged electrodes. The equal numbers of positive and negative ions generated at a constant rate are separately collected by the two charged electrodes. In the absence of wind, the potential due to space charge is zero at the electrical midpoint between the two collecting electrodes where an electrical probe is situated. Any wind component along the axis, however, causes an unbalance which is sensed by a small current in the probe that is amplified and recorded. This development effort differs from prior work in its concentration on the following goals: (1) linear output with velocity, (2) a true cosine law response to an off-axis airstream, (3) a usefully large analog signal capable of simple readout at very low wind speeds.
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 01, 1969
- Accession Number
- AD0861444
Entities
People
- Alan M. Nathan
- Leon Bennett
- Moises Cytter
Organizations
- New York University