HDE Grower's Toolbox- Digital pH Meter and TDS Water Temperature Purity Salinity ppm Pen for Hydroponic Pool Aquarium Fish Tank Water Quality Digital pen style pH meter is an ideal instrument for anywhere you may need to test pH levels Excellent meter, very accurate and durable. Measuring pH Range: 0.0 - 14.0 pH. Resolution: 0.1 pH. Meter comes with protective plastic case and calibration screwdriver | Measures total dissolved solids (TDS) and temperature TDS Range: 0-5000 ppm (mg/L) , Temperature Range: 0-80 C; 32-176 F | Resolution: 1 ppm; Temp. resolution is 0.1 C/F **Note: Calibration fluid is needed, but not included with this product