Abstract: A spray generator (10) including: a membrane (40) having a perforate portion through which, in use, a fluid is caused to flow when the membrane (40) is vibrated; an electronically-driven or a piezoelectrically driven actuator for vibrating the membrane (40); a chamber (18) for storing fluid for supply to a surface of the membrane (40); and a sealing element (13) located in and movable within the chamber (18) between a first position in which fluid flow from the chamber (18) through the membrane (40) is prevented and a second position in which fluid flow from the chamber (18) through the membrane (40) is allowed.

Abstract: A matric potential sensor (100) arranged to measure the matric potential of a medium and comprising a porous material portion (102a, 102b), arranged to absorb moisture from the medium into which, in use, it is inserted, and an electrode element (100) wherein a non-porous compliant material (606, 608) is provided between the porous material (102a, 102b) portion and the electrode element (100).

Abstract: A spray generator (10) comprising: a membrane (40) having a perforate portion through which, in use, a fluid is caused to flow when the membrane (40) is vibrated; an electronically-driven or a piezoelectrically driven actuator for vibrating the membrane (40); a chamber (18) for storing fluid for supply to a surface of the membrane (40); and a sealing element (13) located in and movable within the chamber (18) between a first position in which fluid flow from the chamber (18) through the membrane (40) is prevented and a second position in which fluid flow from the chamber (18) through the membrane (40) is allowed.

Abstract: An electronic drive system for a droplet spray generation device has a droplet generator with a perforate membrane driven by a piezoelectric transducer. An electronic circuit controls a power supply to control the charging of a capacitor to supply a drive signal to the piezoelectric transducer. The electronic circuit is arranged to control the operation of the power amplifier at substantially its resonant frequency.

Abstract: An electronic drive system for a droplet spray generation device (10) has a droplet generator (II) with a perforate membrane (32) driven by a piezoelectric transducer (31). An electronic circuit controls a power supply (21) to control the charging of a capacitor (22) to a supply voltage providing power to a power amplifier (23) connected to receive electric power from the capacitor and supply a drive signal to the piezoelectric transducer.

Abstract: A system for controlling an electronic driver for a nebuliser or aerosol, the system comprising: an H-bridge driver for connection around a membrane to be driven; a voltage source for applying a voltage to the H-bridge driver; a feedback loop from the H-bridge to a phase shift oscillator, the output of which enters the H-bridge driver; wherein the H-bridge driver includes at least one sense resistor for detecting the phase angle between the applied voltage to the H-bridge driver and the applied current.

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: 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.