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• MOLDED POLYETHERSULFONE (PES) BODY provides compatibility with a variety of
processes.
• MODULAR DESIGN facilitates maintenance by eliminating terminal and mounting brackets
and extraneous hardware.
• INTEGRAL PREAMPLIFIER provides reliable signal transmission.
• DOUBLE JUNCTION, GEL-FILLED, REFERENCE CELL provides high temperature per-
formance, extended service life, and resists the effects of pumping, dilution and contami-
nation.
• OPTIONAL FLOW-POWERED OR ULTRASONIC CLEANING provides trouble-free serv-
ice in difficult applications.
1.1 FEATURES AND APPLICATIONS
The Model 381 Sensor measures the pH or the
Oxidation Reduction Potential (ORP) of aqueous solu-
tions in pipelines, open tanks or ponds. The sensor is
used in most industrial applications including SO
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scrubbers, rinse tanks, plating baths, reverse osmosis
units, and water and waste treatment plants.
The sensor is housed in a molded PES body and has
two O-ring seals with breach lock threads which
secure the PES cover. This provides a waterproof
union for long operating life and easy removal for rou-
tine maintenance.
The modular body design eliminates the need for
internal mounting brackets, terminal brackets and
screws. All components are screw-type or plug-in-
place, allowing for fast simple service.
The integral preamplifier amplifies the high imped-
ance glass electrode signal at the sensor, providing a
transmission capability of up to three miles. The
Rosemount Analytical Inc. method of preamplification
has become the industry standard for reliable pH
measurement. In submersion applications at tempera-
tures greater than 80°C, the preamplifier must be
located in a remote junction box.
A standard feature of the Model 381 is the double
junction, gel-filled reference cell which reduces the
need for special applications engineering where
unknown reference cell contamination, such as sul-
fides, may exist. The gel solution maintains its viscosi-
ty at high temperatures, and resists the effect of
pumping and dilution, resulting in an extended service
life. A choice of wood (Code 20) or ceramic (Code 21)
liquid junction is available to provide resistance to
fouling and subsequent loss of electrical contact
between the reference electrode and process fluid.
In flow applications where crystalline or viscous coat-
ings, such as calcium carbonate or petroleum oils,
may coat the electrode surfaces and impede the sen-
sor's performance, the flow-powered cleaning option
(Code 04) may be used. A specially designed flow
chamber directs the process fluid in a circular path
carrying three Teflon
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balls which clean the electrode
surface, physically preventing accumulation of coating
materials. Flow-powered cleaning is suitable for all
hazardous area applications.
In submersion (Code 02) applications, the ultrasonic
cleaning option may be specified. This assembly
includes the ultrasonic transducer and generator,
mounting hardware, and 20 ft. of interconnection
cable. Ultrasonic cleaning is not suitable for haz-
ardous area applications.
The Model 381 is compatible with all Rosemount
Analytical pH/ORP analyzers. For use with the
1054/2054 Series, 2081 and other pH analyzers
which utilize a PT-100 automatic temperature com-
pensator order the Model 381 pHE.
MODEL 381 pH/ORP SECTION 1.0
DESCRIPTION AND SPECIFICATIONS
SECTION 1.0
DESCRIPTION AND SPECIFICATIONS
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Teflon is a registered trademark of E.I. du Pont de Nemours & Co.