Importance

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Abstract

There is disclosed apparatus for monitoring the concentration levels of halogen gas in a gaseous atmosphere as confined in an enclosure over a relatively extended period of time. Such monitoring apparatus includes a sensor including first and second electrodes disposed to define a space therebetween through which the gaseous atmosphere flows and a voltage source for applying a voltage between the first and second electrodes whereby an ionization current flows to the first electrode. A control mechanism illustratively in the form of a programmed microcontroller monitors the ionization current collected by the first electrode as the output signal of the sensor, to determine an increase therein as would be indicative of a halogen leak. Upon determining an increase of the sensor output signal above a predetermined difference, the control mechanism removes the energization from the halogen sensor whereby the ionization current is terminated and the life of the sensor extended. The control mechanism further causes an initial reading of the sensor signal to be taken and to be stored, whereby subsequent sensor readings may be compensated by subtracting the stored value therefrom to provide a compensated output indicative of the increased halogen level with respect to the initial background reading thereof. The relatively small halogen sensor output is amplified by a variable gain amplifier, whose gain setting is automatically set over a large range of sensitivities.

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First Claim