The SPECTRACAP sensor measures oxygen concentration optically by measuring the absorption of light from a tunable diode laser. The device can be flange-mounted directly into a process without sampling or sample conditioning equipment. This provides the user real-time measurement data without sampling or sample switching delays. The stainless steel probe tolerates aggressive chemicals and excessive amounts of moisture. For processes with high temperatures, elevated pressures or excessive solids content, an optional sampling cell is available for the transmitter. A stainless steel mesh filter protects the probe optics from dust and dirt. An optional hydrophobic, porous PTFE filter is also available.