A sensor for detecting particles, in particular, soot particles, is described. The sensor includes a sensor element having at least two measuring electrodes, which are situated on a carrier substrate, and a protective tube assembly having at least one outer protective tube and one inner protective tube. The sensor element is situated in the inner protective tube in a longitudinal extension direction. The outer protective tube and the inner protective tube are designed to permit the particles to access the sensor element in a direction deviating from the longitudinal extension direction.