Sondex Wireline Limited

Kenneth Tomkins

Guy Harvey Mason

James Andrew Gulliver

Paul Franklin Steel

Andrew John Stevens

Derek George Hayes

A peak hold circuit configured for use in a downhole sensor includes a long tail pair circuit, a correction circuit, and a current mirror circuit. The current mirror circuit includes two current mirrors connected to a long tail pair formed by a first transistor and a second transistor. The current mirror also includes a first resistor and a second resistor connected to a third transistor. The first transistor is connected to a correction transistor of the correction circuit. The value of the first resistor is selected to be essentially equal to the same value as the second resistor so that when the long tail pair is balanced, the current flowing through a collector of the second transistor is equal to the current flowing through the first transistor, causing the correction transistor to switch off.

Wide temperature range peak hold circuit

An apparatus for determining the concentration of a conductive fluid present in a fluid filled bore hole is described. Such apparatus are known as water hold-up meters and are frequently used in oil, gas and water filled bore holes. In bore hole applications, data bandwidth between a down hole device and the surface can be limited, while determining water hold-up based on down hole measurements can be data intensive. A technique is proposed for calculating the water hold up that requires less data to be transmitted between the down hole device and the surface.

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Hampshire, United Kingdom

Kenneth Tomkins