The REED R3100SD is a data-logging meter built for water-quality monitoring, tracking conductivity, TDS, and salinity in one handheld unit with automatic temperature compensation and a backlit LCD. Like its pH sibling, it logs to an internal SD card at operator-set intervals and exports straight to spreadsheet format for later review. The -NIST version adds a traceable calibration certificate with documented uncertainty data, useful where measurement records need to hold up to an audit.