Air Quality Meters features: Yieryi do-66 pen type intelligent dissolved oxygen analyzer digital dissolved oxygen tester for aquarium, fish tank, aquaculture Color: we send based on the color or size of the main image of the product page. Quantitywe send based on quantity on title, if there is no quantity in the title, we send based on description. yieryi DO-66 pen type intelligent Dissolved Oxygen Analyzer LCD digital dissolved oxygen tester for Aquarium, fish tank, aquaculture The DO-66 type pen type intelligent Dissolved Oxygen Analyzer (hereinafter referred to as the instrument) is designed to facilitate the user to carry the operation on the spot. The instrument can be divided into two parts: the sensor and electronic unit. The sensor adopts thin film dissolved oxygen electrode. The electronic unit is an integrated operational amplifier + microcomputer chip with automatic temperature compensation function. Technical parameters: 1.Measurement range: DO: 0~199.9%; 0~16.50mg/L Temperature :050; 32~122 2.Resolution: DO: 0.1%; 0.01mg/L Temperature 0.1; 32.18 3.Accuracy: DO: 1.5% F.S Temperature 1;33.8 4.Residual current: No more than 0.15mg/L 5.Response time: No more than 15 seconds 6.Temperature compensation: 050 7.Power supply: 2 *AAA batteries (not included) 8.Working temperature: 050 9.Dimensions: 207*32*36mm 10.Weight: 85g (No batteries included) Operation : 1. Installing batteries. 2. Connect the DO electrode to the corresponding input. 3.Press ON/OFF key to turn on the machine, take off the electrode protector and insert the electrode into the solution to be tested. 4. Press [% and mg / L] key for % and mg/L display conversion. 5. The dissolved oxygen concentration of the solution (mg/L or %) can only be read after the display of the instrument is stable. 6. Press the C/F key to switch between Celsius and Fahrenheit. 7. Press the ON/OFF key to turn off the power. Calibration 1.Rinse the electrode well with DI water or rinse solution. press ON/OFF to turn on the machine. Dip the electrode into the zero oxygen solution for at least 3 minutes, and keep shaking gently until the display value stabilizes. 2. Press and hold the ON/OFF key until the second line of display shows "CAL" character, continue to shake the electrode gently, when the display value is stable, press [% / L/mg] key, it shows DO value 0%, complete the zero calibration. 3.Clean the electrode, dip the electrode into the saturated dissolved oxygen solution and keep shaking the electrode gently until the displayed value is stable. 4. Shake gently and press ON/OFF key until the second line of the display shows "CAL" character, then press /F key, the DO value of 100.0% is shown at this time, the slope correction is finished. *Note: If you accidentally enter the calibration state (the second line displays CAL characters) due to an operation error, press the [ON/OFF] key briefly to exit. Supplementary note for calibration 1. Preparation of oxygen free water Configure 250ml of 5% sodium sulfite solution, you can add the right amount of cobalt chloride as a catalyst. 2.preparation of saturated dissolved oxygen water Take 300 to 500 ml of distilled water, at a relatively stable temperature, use an air pump to aerate the distilled water for at least 15 minutes.