Abstract: In a system for applying sprayed droplets from a nozzle located in an environment with changing conditions affecting droplet size, a method of controlling droplet size comprising locating a droplet size measurement system at a location downstream from an outlet of the nozzle; receiving at a processor data describing droplets measured by the droplet size measurement system; determining at the processor a measured droplet size distribution from the data; inputting the measured droplet size distribution to a control algorithm in the processor; comparing the measured droplet size distribution to a target droplet size distribution; and outputting from the control algorithm a at least one signal corresponding to a parameter of the system for effecting a change in the droplet size distribution.

Abstract: An oxygen number density or concentration sensor including a sampling luminescent oxygen probe located in a fluid environment, and a gas impermeable enclosure located in the fluid environment and a reference luminescent oxygen probe located within the gas impermeable enclosure, wherein the sampling and reference luminescent oxygen probes are formed by an ideal PSP. A predetermined fixed oxygen number density or concentration is provided within a medium contained in the gas impermeable enclosure. A detector receives signals corresponding to luminescent emissions of the sampling and reference probes. A processor determines a number density or concentration of oxygen in the fluid environment from a signal generated at the sampling probe with reference to an oxygen number density or concentration dependent signal generated at the reference probe.