Excelvan TDS & EC Meter,White Conductivity Pen Water Quality Tester Meter Water Testing Hydroponics&nbsp; - Combination of TDS meter and EC meter - Lock Function: easy to read and record.The instrument will lock the reading - Auto shut-off: Turn off automatically after 5 minutes of non-use,conserve batteries - The temperature can choose Celsius and Fahrenheit - LCD screen ,easy to read and record