The HM Digital QC-1 Quick Check TDS/Conductivity Monitor checks the level of Total Dissolved Salts (TDS) and conductivity. The monitor displays bright LED green light indicating a good water quality and red light indicating service required. It has 8 programmable set points. The monitor is factory calibrated to 100 ppm NaCl, re-calibration is unnecessary. It is excellent for de-ionization and Reverse Osmosis. The range is 0-5000 ppm and accuracy is +/-3%. It has convenient fittings that 1/4 inches and the cable length is 24.5 inches. The dimensions 7.6 x 2 x 4.7 cm (3 x 0.8 x 1.9 inches).