The HI-98129 Combo waterproof tester offers high accuracy pH, EC/TDS and temperature measurements in a single tester. The waterproof Combo (it even floats) has a large easy-to-read, dual-level LCD and automatic shut-off. pH and EC/TDS readings are automatically compensated for the effects of temperature (ATC). Replaceable pH electrode cartridge with an extendable cloth junction. HI-98129: reading of 0 to 3999 μS/cm // HI-98130: reading of 0 to 20 mS/cm.