Abstract: One disclosed optical computing device includes a sampling window arranged on a housing, an electromagnetic radiation source configured to emit electromagnetic radiation, the electromagnetic radiation being configured to optically interact with a substance outside of the sampling window, at least one integrated computational element (ICE) core arranged to optically interact with the electromagnetic radiation, and a detector arranged to receive the electromagnetic radiation following its optical interaction with the substance and the at least one ICE core and generate an output signal corresponding to a characteristic of the substance, wherein the electromagnetic radiation impinges upon the surfaces of the sampling window at an angle of incidence from normal to the sampling window, and wherein specular reflected light reflects off the sampling window at an opposing angle of incidence, the specular reflected light emanating away from the sampling window such that it is not detected by the detector.

Abstract: Various embodiments include systems and methods to provide selectable variable gain to signals in measurements using incident radiation. The selectable variable gain may be used to normalize signals modulated in measurements using incident radiation. The selectable variable gain may be attained using a number of different techniques or various combinations of these techniques. These techniques may include modulating a modulator having modulating elements in which at least one modulating element acts on incident radiation differently from another modulating element of the modulator, modulating the use of electronic components in electronic circuitry of a detector, modulating a source of radiation or combinations thereof. Additional apparatus, systems, and methods are disclosed.