The AutoAqua Digital Inline TDS Titanium S3 monitors three points in your filtration line at once — typically tap water, mid-filter, and final RO/DI output — giving the most complete picture of the AutoAqua inline TDS lineup for tracking exactly where filtration is working and where it isn't. Probe: titanium, resists corrosion, three 1/4in push-connect union tees for multi-point installation, magnetic mount Display: backlit LCD, single-button operation Power: CR2032 lithium battery, auto-off after 3 minutes, low-battery indicator, ~1 year battery life Range: 0-999 ppm, 1 ppm resolution, ±2% accuracy Calibration: factory-tested, with a manual calibration option Includes: Titanium S3 inline TDS meter, CR2032 battery, three 1/4in push-connect union tees.Three-stage monitoring makes it easy to pinpoint which stage of your RO/DI system is losing efficiency — a jump in TDS between any two of the three points tells you exactly which filter stage to replace next.