3in1 Digital TDS EC TEMP Meter Water Quality Tester Purity Filter Pen 0-9990ppm Feature: For checking TDS/salt (NaCl) levels freshwater aquariums, ponds and water purification systems. 3-in-1 smart pen combines TDS, EC, and a temperature meter for improved accuracy. With an Automatic Temperature Compensation and the measuring range of 0-9999 ppm +/- 2%. 4 Display modes: Press SHIFT button: TDS - ppm & °C, EC - µs/cm & °C, TDS - ppm & °F, EC - µs/cm & °F. Lock function, easy to read and record, press HOLD button then remove from test solution. The instrument will automatically shut down after 5 min of inactivity.  Measurement Range: Conductivity: 0 - 9999µs/cm; TDS: 0 - 9999ppm; Degrees Celsius: 0.1 - 80.0°C, Fahrenheit: 32.0 - 176.0°F Resolution: TDS: 1ppm; EC: 1µs/cm Battery: 1*3.0V (CR2032) (built-in) Accuracy: ± 2% Net weight: 1.94oz (55g) Size: 6 x 1.2 x 0.6 inches (154 x 30 x 14 mm)   Package Includes: 1 x TDS & EC Meter 1 x Carrying bag 1 x User's manual How to use: STEP 1: Remove the electrode protective cap before use STEP 2: Press the ON/OFF button, and immerse the meter into the solution. (The solution should not over the immersion line) STEP 3: After the numerical display is steady, press the HOLD button and take it out of the solution for checking the result STEP 4: Wipe clean the electrode after using, turn off the meter and replace the protective cap