HI 4221 Research Grade Meter with Calibration Check™ pH/ORP and Temperature HI 4221 is a research grade pH, ORP and temperature benchtop meter. The user interface of HI 4221 is fully customizable, and it is capable of showing the measurements in various modes: basic measurement with or without GLP information, graph or logging data. This instrument offer multi-language support and contextual help is available ... Read More »