Greisinger gmh 5530 ph waterproof handheld measuring device for ph redox greisinger gmh 5550 the greisinger gmh 5550 ph is a waterproof handheld measuring device for ph redox designed for measuring ph and orp potentials with the help of adequate electrodes the electrode is connected via bnc socket please note different electrode types are needed for ph and orp measurementsthe gmh 550 ph is supplied with an analouge output and data logger as standard it is possible to connect a temper