Designed for water quality experts, the Hach HQ411D Laboratory pH-Meter is an advanced laboratory meter that takes the guesswork out of measurements. HQD meters connect with smart Intellical electrodes that automatically recognize the testing parameter, calibration history, and method settings to minimize errors and setup time. The advanced HQD Laboratory Meter is designed to withstand years of continuous lab use. HQD meters feature a simple user interface that does not require manuals or training to operate. The Intellical PHC201 is a digital robust plastic body, combination pH electrode with a non-refillable, gel-filled double-junction reference and built-in temperature sensor. PHC201 is intended for laboratory use. The PHC201 has a ceramic pin reference junction and is ideal for measuring pH in general water quality applications.