An apparatus for measuring fluid characteristics includes: a solid transparent body including a plurality of internally reflective surfaces defining a n-sided base having a polygonal shape and having at least three sides, each reflective surface forming a side of the polygonal shape, the plurality of surfaces configured to direct the electromagnetic radiation beam along a path within the solid transparent body from an entry area to an exit area on the solid transparent body; an electromagnetic radiation source coupled to the entry area on the solid transparent body; and a detector coupled to the exit area on the solid transparent body and configured to receive at least a fraction of the reflected electromagnetic radiation beam, the detector configured to generate a signal based on the received electromagnetic radiation beam and transmit the signal to a processor for at least one of analysis of material characteristics and data storage.