An instrument using hot-wire technology to measure droplet size distributions in the 1 to 450 µm size range is discussed. Such instrumentation has several advantages over present techniques which are dominated by a variety of laser light scattering approaches. The major advantages are: (1) the hot-wire instrument is readily portable; (2) no careful alignment is necessary; and (3) the instrument is available at a fraction of the cost of optical instruments.

The present paper discusses some details of the droplet/wire interaction, for example, effects of the wire mounting posts, “grazing” interactions, aerodynamic effects, and liquid variation. Also discussed are the means of raw data corrections to obtain a variety of mean droplet sizes, volume concentration, and volume flow rates.

Limitations will be discussed along with examples of where the instrument can best be utilized.