Features: Lock function - Makes it easy to read and record, the instrument will lock the reading result. After the numerically result gets stable, press HOLD button then remove the meter out of test solution to read. 4 Display modes: press SHIFT button: TDS - ppm & °C, EC - µs/cm & °C, TDS - ppm & °F, EC - µs/cm & °F. 9-minute Auto Shut Off feature, so battery won't run down. Elbourn pH & TDS Meter Combo Elbourn pH&TDS Meter is ultra accurate, reliable and easy to use. PH meter could measure pH and temp value; TDS Meter (include EC, TDS and Temp function) is 3 in 1 ergonomically designed tester meter. It can be widely used in all water quality testing situations, Water Purification Applications, Aquaculture, Hydroponic, Pool & Spa, Colloidal Silver, Water Treatment and so on. Note: TDS Meter had been calibrated by manufacturer in advance. 1413 solution is unnecessary and not included. Specifications: PH Meter Measure Range : 0.00 - 14.00 pH Resolution : 0.01 pH Accuracy : 0.05 pH Calibration: Three Points Automatic Calibration Button Power Supply: 2 x 1.5V LR44 Button Battery (keep using more than 500 hours) Dimension:155mm*31mm*18mm Weight:50g 3-in1 TDS EC Temperature Meter Conductivity: 0 - 9990 µs/cm TDS: 0 - 9990 ppm (parts per million) Degrees Celsius: 1.0 - 80.0°C Fahrenheit: 32.0 - 176.0°F Accuracy: 2% Net weight: 51g Size: 154 x 30 x 14 mm Tips: TDS = Total Dissolved Solids, which is any salt, metal or mineral in the water. Note: This ppm meter can't test sea water.