Digital TDS Water Quality Test Pen Aquarium Pool Hardness Purity Monitor Test Tool TDS Meter   Feature:    Lock function.   Easy to read and record, the instrument will lock the reading;   5 minutes automatic shutdown function, the battery will not run out;      Specification:   Measuring range:   Conductivity: 0-9990us/cm   TDS:0-9999ppm   Celsius: 0.1-80.0℃   Fahrenheit: 32.0-176.0°F   Accuracy: ±2%   Size: 154*30*14mm/6.06*1.18*0.55"      Use steps:   Before use, please remove the electrode protective sleeve;   Press the key and put the electrode into the solution to be tested;   After the value is stable, press the HOLD key to take out the reading;   After reading, press the switch key, wipe the electrode clean, and put the electrode protective sleeve into it;      Instructions for use:   TDS & conductivity switch;   The meter displays the TDS value at the factory. If you want to measure the conductivity of the solution, please touch the SHIFT key lightly, and the meter will switch automatically;   Automatic temperature compensation;   The instrument has automatic temperature compensation function in measurement mode;      Temperature switch:   Touch the SHIFT key twice in a row to switch between degrees Celsius and Fahrenheit, and the meter defaults to degrees Celsius;      Maintenance:   Keep the electrode clean and cover the electrode protective sleeve. If not used for a long time, please take out the battery      Calibration method:   (The new pen does not need to be corrected within 5 years)   1. Preparation tool: solution with known value, utility knife or small screwdriver   2. Tear off the black rubber panel (you can use a utility knife or a small screwdriver to extend along the bottom corner of the button)   3. Press the first ON/OFF switch button to turn on the power;   4. Remove the electrode protective sleeve;   5. Put the electrode into a solution with a known value, and gently stir in the solution to drive off bubbles around the electrode;   6. There is a small correction screw on the left side of the middle button. Insert a small screwdriver or a tool that can be inserted into it. Turn left and right to adjust to the value of the known solution to complete the calibration.      Note:   Due to the different monitor and light effect, the actual color of the item might be slightly different from the color showed on the pictures. Thank you    Please allow 1-3mm measuring deviation due to manual measurement.            Packages:    1 X Water Quality Test Pen