Logarithmic converters and their application to the measurement of transmitted light
AssigneeInovelf
InventorsHerve Arribard, Bruno Cornut, Gilbert Passade, Claude Sesques
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Abstract
The object of the present invention is the improvement of logarithmic amplifiers and/or converters and the applications of such devices in particular to photometric analyzer apparatuses. These amplifiers are characterized by the fact that they are linear with an amplification gain programmable by the .mu.P computer and that they may be preceded optionally by a reference voltage system. Application to the measurement of light transmitted by samples.
Claims24
An assembly for the conversion of an analog signal into a digital logarithmic signal, comprising:
- a linear amplifier including means for receiving and linearly amplifying an analog signal;
- gain varying means for varying the gain of said linear amplifier;
- an analog-to-digital converter including means for receiving said linearly amplified analog signal from said linear amplifier and converting said linearly amplified analog signal into a digital signal;
- a computer including means for receiving said digital signal and control means for controlling said gain varying means to reduce the gain of said amplifier when the magnitude of said digital signal exceeds a predetermined limit indicative of the saturation point of said analog-to-digital converter, and further including means for converting said digital signal into a digital logarithmic signal according to a predetermined relationship between the logarithm of the digital signal and the gain of said linear amplifier, and wherein the reduction in said gain by said control means is limited to a predetermined value which does not impair the resolution of said analog signal such that, for a particular analog signal, a plurality of adjacent gain levels may be selected by said control means.
An analysis device for analyzing luminous transmission, comprising:
- a luminous source adapted to emit a light beam;
- an optical system arranged to concentrate the light beam from the source onto at least an analytical cell containing a sample to be analyzed;
- a detector receiving the light beam passing through the analytical cell and delivering an analog electrical signal representative of the intensity of said light beam;
- and an assembly for the conversion of said analog signal into a digital logarithmic signal, said assembly comprising:
- a linear amplifier including means for receiving and linearly amplifying an analog signal;
- gain varying mans for varying the gain of said linear amplifier;
- an analog-to-digital converter including means for receiving the lineraly receiving the analog signal from said linear amplifier and converting said amplified analog signal into a digital signal;
- a computer including means for controlling said gain varying means to reduce the gain of said amplifier when the magnitude of said digital signal exceeds a predetermined limit indicative of the saturation point of said analog-to-digital converter, and further including means for converting of said digital signal into a digital logarithmic signal according to a predetermined relationship between the logarithm of the digital signal and the gain of said linear amplifier, and wherein the reduction in said gain is limited by said control means to a predetermined value which does not impair the resolution of said analog signal such that, for a particular analog signal, a plurality of adjacent gain levels may be selected by said control manes.
Dependencies are inferred from the claim text.