[5-in-1 Digital Aquarium Salinity Tester] ① Measures water temperature in Celsius and Fahrenheit ② pH (Pondus Hydrogenii) ③ Salinity ④ TDS ⑤ EC. Simultaneously displays 5 parameters, intuitive and convenient. Equipped with a battery indicator to monitor battery status at any time. Automatic shut-off after 5 minutes of operation saves energy. Features include automatic range switching and automatic temperature compensation. [How to Use] Power On/Off: Press and release the button for 1 second to turn the device on or off. It will automatically shut off after 5 minutes of inactivity. Switching the display interface: Press and hold the button for 2 seconds to switch between display modes. [Display interface switch and automatic temperature compensation] The LCD screen orientation can be changed according to preference or the operating environment. The switching sequence is [General]-[Right Hand]-[Left Hand]-[General]. The tester can automatically compensate for temperature errors based on changes in water temperature, providing more accurate measurement values. Function selection: Press and hold the button for 5 seconds to access the function selection menu. You have three functions to choose from: pH-CAL, EC-CAL, RESET, supporting pH calibration, EC calibration, and factory reset.