This user guide provides instructions for using the Orion StarTM and Star Plus Series pH/ISE meters. It includes sections on the display, keypad, preparing the meter, setting up the meter, and techniques for measuring pH, ORP, dissolved oxygen, conductivity, and ISE parameters. The guide covers connecting electrodes, calibrating sensors, taking measurements, and maintaining the meter. It is intended to help users operate the meter and sensors to obtain accurate measurement results.