The HM COM-300 professional tester integrates four core testing functions: pH, EC, TDS and temperature, delivering all-around water parameter detection for industrial, laboratory and home use. Built with IP67 waterproof white ABS housing, this pen-style detector supports two switchable TDS conversion factors (0.5 NaCl & 0.7 442) and 0–9990μS EC measuring range, paired with automatic temperature compensation to offset reading deviations from varying liquid temperatures. Its large dual-display LCD screen shows real-time data and temperature simultaneously, equipped with handy data hold, auto power-off and low-battery reminder for user-friendly operation. The replaceable probe sensor enables long-term service, and one-button digital calibration simplifies regular maintenance. Factory pre-calibrated out of box, it suits hydroponic planting, aquaculture, drinking water filtration, swimming pool maintenance, lab reagent testing and wastewater inspection. Compact, lightweight design with a protective probe cap and matching lanyard allows portable on-site sampling for daily and professional water quality monitoring.