Abstract: An electronic gas flow triggering circuit for use in an aerosol drug dispensing device has a voltage source and a self-nulling circuit to which voltage is supplied from the voltage source. A hot wire anemometer filament forms a component of the bridge circuit which is adapted to maintain a constant resistance of the anemometer filament, the bridge drive voltage being dependent upon the gas flow across the anemometer filament. A comparator compares the bridge output voltage with a reference voltage and provides a triggering signal to operate the device if the bridge drive voltage is greater than the reference voltage.

Abstract: A method of forming a perforate membrane (1) is disclosed for use in a liquid transport device. The membrane has at least plural nozzles (10) formed therethrough. Each of those nozzles has a throat portion (12) opening at opposite end through opposite surface (2?) of the perforate membrane and a smoothly curved outwardly diverging portion (11) extending from the first end of the throat portion to the first surface (2) of the perforate membrane. Laser energy is applied selectively to the first surface (2) of the membrane in the form of a pulsed, focused beam to form the nozzles (10) and thereafter the first surface (2) of the membrane and the surface of the diverging portion (11) of the nozzles (10) are electro-polished to remove surface imperfections. The electro-polishing is controlled so as to remove material from the surface of the diverging portion (11) of the nozzles to a depth less than the length of the throat portion (12).