28090 Mini Liquid Level Sensor Parallax 28090 Mini Liquid Level Sensor is designed to be inserted vertically into wet environments to detect liquid levels from 0 to 1.88in (48mm) or as an alarm. The 28090 sensor has a single analog output, which may be directly connected to the Propeller Activity Board 4-channel A/D converter or easily interfaced with the MCP3002 A/D with a FLiP Multicore Microcontroller. Parallax 28090 Mini Liquid Level Sensor is ideal for water level alarms for moisture-sensitive environments, water level indicators for fluid reservoirs, and stream-level indicators when used in a controlled reservoir (stream well).