Central Research Laboratories Limited

Monica Backes

John Robert Dodgson

Malcolm Trayton Austen

John Edward Andrew Shaw

Alastair Sibbald

Anthony Robert Corless

Mark Seymour

Richard Lynn Hedgeley

David Wenn

Analytical sampling device

A gas sensor is described which is particularly well suited as a carbon monoxide (CO) sensor in a self test gas sensor. The sensor includes a number of aspects which may or may not be used in conjunction with one another. A first aspect is an embodiment which reduces electrical interference (or cross-talk) between a test or gas generating cell and a sensing cell. In one embodiment, baffles are provided to prevent cross-talk. In another embodiment a switching circuit ensures that a test gas generator is operational only when the gas sensor is disconnected from a current source. A second aspect is an embodiment which includes an improved wick which is in close proximity with an electrode and ensures electrolyte is always in contact with the electrode. In an alternate embodiment a solid polymer electrolyte is used between the electrodes. A third aspect is an improved catalyst which reduces the reaction energy and thereby renders the sensor more sensitive. The catalyst is also cheaper than platinum. Overall the gas sensor uses less components than existing gas sensors and is therefore cheaper and easier to assemble and more reliable.

Gas sensor

Apparatus for dispensing a predetermined volume of a liquid ( ) comprises a reservoir ( ) for the liquid, a channel ( ) provided with an outlet ( ) for conveying the liquid ( ) from the reservoir to the outlet, and means for generating a pulse of gas. The apparatus is arranged such that the flow of gas causes a predetermined volume of liquid to be ejected from the outlet. The outlet comprises a pair of openings in the channel which face one another, the liquid being retained between the openings by surface tension in the absence of a flow of gas. The gas flow is directed towards one of said openings in use. The apparatus may be used to dispense volumes of a liquid reagent in the range 1 nl to 2 &mgr;l. The apparatus avoids contamination of the liquid, and dispensing head construction allows devices to be low cost disposable units. The apparatus is less sensitive to liquid viscosity than existing devices.

Apparatus for dispensing a predetermined volume of a liquid

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Ealing, United Kingdom

Monica Backes