Feature: Compact and portable pen design,easy to operate and storage. Large and clear LCD with backlight, easy to read and accurately measuring functions. The tester is made of high quality electronic components to ensure high accuracy. Suitable for water sources, aquariums, hydroponics, swimming pools and other water systems. The resolution of ORP tester is 1 mv, very high sensitivity. Specification: Model: ORP2069 Measurement range: 0 - 1999mg/LmV Resolution: 1 mV Accuracy: 5mV Operating voltage: 4*1.5V (AG-13 battery) (No-include) Working temperature: 0- 50 Correction: 1 point correction Operation steps: 1. Remove the protective cover. 2. Touch the ON/OFF switch lightly and turn on the power supply. 3. Put the electrode into the solution under test, shake it gently, and read the display value when the value is stable. 4. Touch the HOLD button to keep the current measured value. If you need to re-measure, press the HOLD button again to automatically remove the holding state. 5. After using, press off the switch, clean the electrodes with distilled water, and put a protective cover on them. Battery installation: If the display is blurred or not, the battery should be replaced in time. When replacing batteries, the top cover can be switched off and replaced. Pay attention to the polarity of batteries. 1. When measuring, shake the instrument gently. Do not let the electrode have bubbles. Otherwise, the measurement results will be affected. 2. Instruments should not be adjusted at will, only if they have been used for a long time or are used very frequently, they should be re-calibrated. 3. If there are some phenomena such as large error of indication number, indication jumping and indication not returning to zero, we should insert the part below the instrument immersion line into alcohol and shake it for several times to clean the sensor. In low temperature or wet condition, the indication value does not return to zero (the last digit load of the display is less than 2), which will not affect the measurement value. Package list: 1 * ORP Tester 1 * Installation tool 1 * User manual Note: The actual product color may deviate from the photo due to light. There may be a slight deviation in the measurement of product.