General Electric Company

Delta Associates, Inc.

Ronald A Gatten

Paul L Patterson

Peter I Granchukoff

A digital acquisition system for use in a computerized radiation tomography system employs track and hold means associated with each channel of the radiation detector in the tomography system. Each channel of the radiation detector is connected to a voltage follower transistor and resistor. A signal from the voltage follower transistor and resistor is applied through a Butterworth filter and amplifier to a transconductance amplifier which provides a signal for application to a charge storage capacitor. The capacitor is connected to the detector channel except during each limited period of time when the charge is held for measurement and conversion to a digital form. The data acquisition system has fewer components, and the simplicity of the circuitry increases the circuit reliability.

Data acquisition circuitry for use in computerized tomography system

A gas stream detection apparatus having a balanced resistive bridge network enclosed within a housing and an electronic power supply for driving the bridge network. The power supply includes a voltage source feeding a voltage-to-current converter with two differential inputs, a current sensing resistor between the converter and bridge, twin feedback paths to the differential inputs, and a large source resistance connected to the voltage source and in parallel with a smaller source resistance, each connected to separate differential inputs. The resistance R of two bridge filaments increase by .DELTA.R when exposed to high sample gas concentration causing variations in a current I supplied to the bridge. As .DELTA.R increases, a bridge output voltage E.sub.O decreases. The dependence of current I on .DELTA.R depends on circuit parameters. The difference between the source resistances permits the voltage source to be non-constant and load dependent. The source output polarity opposes the feedback polarity and under steady state a fixed current I exists. When sample concentration increases, the feedback input decreases causing current I to increase which restores detector sensitivity and provides a linear output voltage response E.sub.O.

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Placerville, CA, United States of America

Ronald A Gatten