Abstract: A single photon counting apparatus comprising a SPAD and a controller. The controller is operable to vary the operating parameters of the SPAD during use in response to a count rate detected by the SPAD. The operating parameters comprising at least one of the voltage across the SPAD during an active period, the voltage across the SPAD during a quench period, the duration of the quench period and the temperature of the SPAD. Particle characterisation instruments comprising the apparatus are also disclosed.

Abstract: In a first aspect of the invention, the three-way ring puzzle has a rectangular housing with a first and second opposite sides. A first series of stems extends from the first side, and a second series of stems extends from the second side. Each stem has an eyelet on its extremity outside the housing and a wire loop is loosely mounted in this eyelet. Each of the stems in the first series aligns with and is joined inside the housing to one of the stems in the second series. A first and second elongated wire bands are respectively mounted in the wire loops on the first and the second series of stems. In another aspect of the present invention, the housing has a cylindrical shape, the stems extend diametrically through the housing and each of the elongated wire bands has a curved shape.

Abstract: In a first aspect of the invention, the three-way ring puzzle has a rectangular housing with a first and second opposite sides. A first series of stems extends from the first side, and a second series of stems extends from the second side. Each stem has an eyelet on its extremity outside the housing and a wire loop is loosely mounted in this eyelet. Each of the stems in the first series aligns with and is joined inside the housing to one of the stems in the second series. A first and second elongated wire bands are respectively mounted in the wire loops on the first and the second series of stems. In another aspect of the present invention, the housing has a cylindrical shape, the stems extend diametrically through the housing and each of the elongated wire bands has a curved shape.

Abstract: A slot diffuser includes a pair of elongate and parallel side walls spaced by pairs of bridges. The bridges include feet that slide along receivers in the side walls such that the bridges can be positioned at any location therealong and provide support to the bridges and stability to the diffuser. The bridges include slots that extend between the side rails and that receive ends of air flow control blades. The air flow control blades include an elongate planar portion supported by rods extending outwardly on either side of the planar portions to support the blades in the slots. At a lower end of each planar portion opposite the rods is a foot that extends perpendicularly outward therefrom. Each side rail includes an inwardly projecting flange that is sized and positioned to slidably receive the foot of an associated blade such that the blade may be manually moved both within the slot and along the flange to properly position the blade during the installation or subsequent modification.

Abstract: A diffuser having side rails and bridges includes different sets of air control blades that are interchangeably mounted on and slidable along slots located in the bridges. The different sets of blades may be interchanged without disassembly of a remainder of the diffuser.

Abstract: A slot diffuser includes a pair of elongate and parallel side walls spaced by pairs of bridges. The bridges include feet that slide along receivers in the side walls such that the bridges can be positioned at any location therealong and provide support to the bridges and stability to the diffuser. The bridges include slots that extend between the side rails and that receive ends of air flow control blades. The air flow control blades have an elongate planar portion supported by rods extending outwardly on either side of the planar portions to support the blades in the slots. The blades are removable without disassembling the entire diffuser. Each bridge has an arcuate cover that reduces air drag and each bridge also has a low profile to further reduce air drag and thus reduce noise produced by the diffuser.

Abstract: A slot diffuser includes a pair of elongate and parallel side walls spaced by pairs of bridges. The bridges include feet that slide along receivers in the side walls such that the bridges can be positioned at any location therealong and provide support to the bridges and stability to the diffuser. The bridges include slots that extend between the side rails and that receive ends of air flow control blades. The air flow control blades include an elongate planar portion supported by slot following pegs extending outwardly on either side of the planar portions to support the blades in the slots. The bridges include a spring mechanism to provide bias to the blades to prevent wedging and rattling. The bridges also include a top arcuate cover that reduces air drag and noise.

Abstract: A digital voltmeter for measuring an input voltage which can lie in any one of M successive ranges comprises an input scaling device which scales the input voltage to produce a voltage lying in a single predetermined range, and which also produces a range signal indicative of the range in which the input voltage lies. An analogue-to-digital conversion circuit then converts the scaled voltage to a corresponding digital signal which has up to N significant decade figures of resolution, where N<M. The voltmeter has a display unit with M decades, each of which represents a fixed order of magnitude of the input voltage, and control means responsive to the range signal to direct the digital signal to the group of N adjacent decades of the display means appropriate to the magnitude of the input voltage.