The Single Particle Soot Photometer-Extended Range (SP2-XR) directly measures refractory black carbon (rBC) in individual particles. It uses the same laser-induced incandescence technology as the DMT SP2-D, but with a modified optical design that allows it to be better suited for long-term monitoring applications. In addition to a smaller footprint, the software and firmware included with the SP2-XR provides final data output in real time without the need for two pass processing.

The SP2-XR utilizes a high optical power intracavity Nd:YAG laser. Light absorbing particles, mainly rBC, absorb energy and are heated to the point of incandescence. The energy emitted during incandescence is measured and a quantitative determination of black carbon mass of the particle is made. This mass measurement is independent of the particle mixing state, and hence the SP2-XR is a reliable measure of the black carbon mass concentration. Since the SP2-XR detects single particles, this highly sensitive instrument is ideal for monitoring in remote environments.