Emerson Rosemount 398R Reference Manual page 4

CAUTION
Special Conditions for Safe Use
1. All pH/ORP sensors have a plastic enclosure which must only be cleaned with a damp cloth to avoid the
danger due to a build up of an electrostatic charge.
2. All pH/ORP sensor models are intended to be in contact with the process fluid and may not meet the
500V r.m.s. a.c. test to earth.
This must be taken into consideration at installation.