The introduction of automated observing systems such as the National Weather Service's (NWS) Automated Surface Observing System (ASOS) has led to significant advances in the ability to automatically report some of the so-called visual elements of the weather observation. However, some parameters still require human augmentation. Drizzle is one of those elements that ASOS cannot automatically detect and for which manual augmentation is required. An ongoing effort in the NWS, called Planned Product Improvement (PPI), seeks to promote the development of new technologies that can enhance current ASOS capabilities. An important part of this effort is to identify reference sensors that can be used to evaluate competing technologies that might be considered for inclusion into the ASOS sensor suite. This paper will report on the early phases of an effort to identify a reference sensor for the detection of drizzle.