An integrated spectral sensing engine is based on a combination of energy sources (illumination) and detectors housed within an integrated package that includes the sample interfacing optics and acquisition and processing electronics. The focus is on a miniaturized sensor system that can be optimized for specific measurements and can be integrated into a manifold-based sample handling system. Design and fabrication components are selected to support high volume manufacturing of the sensors. Spectral selectivity is provided by either continuous variable optical filters or fabricated filter matrix components. The spectral response of the primary sensors covers the range from the visible (400 nm) to the near-infrared (1100 nm), as defined by the availability of suitable low-cost solid-state detector devices. Provision is made to extend the range into longer wavelengths, and to shorter wavelengths for filter-matrix devices. A broad selection of measurement modes is defined and these include transmittance/absorbance, turbidity (light scattering) and fluorescence. On board data processing not only provides the primary data acquisition, as well as data massaging and the display and output of computed results. The targeted application of the spectral sensing devices are for water, pulp and paper, chemical and petroleum based industries. Alternative packaging regimes and the production of lower cost sensing devices can lead to the use of the spectral sensing devices in the medical, clinical, forensic and consumer based areas of application.