Operator Manual: Spinning Pinhole for the Cloud Droplet Probe (CDP)

The CDP uses two optical detectors to accurately sense and size particles passing through the CDP sample volume. These detectors are called the sizer and the qualifier. The CDP uses these detectors to determine whether particles fall within the instrument’s depth of field. The depth of field is the region of the sample where the laser is uniformly illuminating particles, and the CDP typically only sizes particles that fall within this region. The sizer and qualifier must be aligned both spatially and temporally, or else particles will generate non-concurrent electrical signals which will be rejected as noise or improperly sized.