In one embodiment, a drop detector includes a light source for illuminating drops passing through a drop zone and a light detector near the light source for detecting light scattered off the drops back toward the light source. In another embodiment, a drop detector includes a light source operable to emit a beam of light for illuminating drops passing through a drop zone and a light detector positioned near the light source to detect substantially only light scattered off the drops at a scatter angle θ in the range of 177° to 180°, where θ represents a direction of scattered light measured with respect to an axis of the light beam with θ=0° lying along the axis in a direction of travel of the light beam and θ=180° lying along the axis opposite the direction of travel of the light beam.