Plessey Overseas Limited

John P Auton

Roger William Whatmore

Paul C Osbond

A device for measuring the liquid content of a gas, as for example measuring the liquid water content in the atmosphere. The device employs a probe fabricated in part from a material which is thermally self-stabilizing and which preferably has a positive temperature coefficient. In use the probe is electrically heated and disposed in a flowing gas or is adapted for movement through a static gas so that droplets of liquid are deposited on the surface of the probe. Means is provided for detecting a change in the electrical resistance of the probe in response to a change in the heat loss rate due to the integrated evaporation of droplets of liquid from the surface of the probe. The temperature of the gas, the degree of relative movement between the probe and the gas, and the gas pressure are also sensed so that when their measurements are processed with a measurement dependent on the change in the electrical resistance of the probe a measurement is obtained of the liquid droplet content in the gas. A particular application for the device is that of measuring the liquid water contents in the air flowing around helicopters and other aircraft, so that the crew can be given warning when they are flying into icing conditions.

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Cambridge, United Kingdom

John P Auton