An ultraviolet (UV) light absorption sensing system (100) includes a UV light source (110) configured to provide a UV sample beam (115) of light toward a still or flowing fluid sample (117) along a central axis (118) of a test cell (120), wherein the central axis (118) is substantially orthogonal to a direction of fluid flow. A reference light source (130) is configured to provide a reference beam (133) along the central axis (118) of the test cell (120). A first detector (140) is positioned to detect a first portion (128) of the UV sample beam (115) and a first portion (138) of the reference beam (133) that traverse the test cell (120). A second detector (142) is positioned to detect a second portion (146) of the UV sample beam (115) and a second portion (148) of the reference beam (133) directly from the UV light source (110) and reference light source (130).