The RAH-DL1S data logger is an electronic device that automatically collects and records data over a period of time from the Hydro Instruments Residual Chlorine Analyzers.

The data logger utilizes an internal flash memory card for data storage and is programmable as to how often data from the attached residual analyzer is captured and stored. This allows for a comprehensive look of the sample water conditions being monitored over time similar to that of a circular chart recorder.