Portable LCD Screen Test Pen Water Quality Monitor Digital TDS & EC Meter Kit

4 Display Modes: TDS - ppm & °C, EC - μs/cm & °C, TDS - ppm & °F, EC - μs/cm & °F. (Press SHIFT button to convert). TDS: 0 - 9990 ppm (parts per million). Lock function: Makes it easier to read and record, Press HOLD button then remove from test solution.

eBay