PPH-500F series industrial pH models can be matched with different types according to different application scenarios, including: sewage, conventional models used in conventional industrial scenarios, salt-free bridge models for dirty and messy environments, and tetrafluorosalt bridges with ion traps for high salt, high heavy metal ions, and high ammonia ion scenarios; at the same time, according to different water quality conditions, different sensitive membranes can also be matched, including high temperature type, low temperature type, acid and alkali resistant type, hydrofluoric acid resistant type, low impedance type, etc.