The Hach SensION1 Portable pH Meter is a basic inexpensive meter which produces reliable result
WTW 330i Handheld pH Meter A robust and waterproof battery-operated pH/mV meter with built in datalogger and real-time clock. Optimized for on-site and field use, but also can be used in the laboratory.
The LeveLine is a water level and temperature recording device that has been specifically designed for long term water level logging. It includes its own internal lithium battery for years of self supplied power and a huge internal memory for year upon year