The HI3M is a rugged all around waterproof meter for easy pH/EC/TDS measurements. The HI3CM has all the popular features of the HI3M and will also display °C with the press of a button. The HI3CM has an added Cal-Check feature that can assess the calibration status of the specialized probe in seconds. Accuracy is ensured with ATC and an advanced sensor which completely eliminates polarization and oxidation problems. Comes complete with probe, battery, calibration, cleaning & Cal-Check solutions.