Rosemount Analytical 381 Data sheet
• ADVANCED ON-LINE SENSOR DIAGNOSTICS
(Model 381+ only), for use with the Models 54e
pH/ORP and 1055 Analyzers and 81, 3081, 4081,
5081-P, and Xmt-P pH/ORP Transmitters, predict
and identify process-related sensor failures.
• MODULAR DESIGN facilitates maintenance by
eliminating terminal and mounting brackets and
extraneous hardware.
• DOUBLE-JUNCTION, GEL-FILLED REFERENCE
CELL provides high temperature performance,
extended service life, and resistance to the effects
of pumping, dilution, and contamination.
• MOLDED POLYETHERSULFONE (PES) BODY
provides compatibility with a variety of processes.
• OPTIONAL FLOW-POWERED CLEANING provides
trouble-free service in difficult applications.
Model 381 pH/ORP
Insertion/Submersion Flow Through Sensor
Product Data Sheet
PDS 71-381/rev.E
October 2010
Continued on page 2
FEATURES AND APPLICATIONS
The Rosemount Analytical Model 381 Sensor measures the pH or the Oxidation Reduction Potential
(ORP) of aqueous solutions in pipelines, open tanks, or
ponds. The sensor is suitable for use in most indus trial
applications, including water and waste treatment
plants.
The Model 381+ features a stainless steel solution
ground. The solution ground provides advanced sensor diagnostics for preventative maintenance when
used with the Models 54e pH/ORP and 1055 analyzers and 81, 3081, 4081, 5081-P, and Xmt-P pH/ORP
transmitters. Sensor diagnostics result in time and
money savings by reducing the guesswork in sensor
maintenance and replacement requirements.
The sensor is housed in a molded PES body and has
two O-ring seals with breach lock threads that secure
the PES cover. This provides a waterproof union for
long operating life and easy removal for routine maintenance.
The modular body design eliminates the need for
internal mounting brackets, terminal brackets, and
screws. All components are screw-type or plug-inplace, allowing for fast simple service.
The integral preamplifier conditions the high impedance glass elec trode signal at the sensor, providing a
transmission capability of up to 1000 ft (304.8 m). The
Rosemount Analytical method of preampli fication has
become the industry standard for reliable pH measurement. In submersion applications at temperatures
greater than 80°C, the preamplifier must be located in
a remote junction box or in the instrument.
A double-junction, gel-filled reference cell, a standard feature of the Model 381, improves sensor life
when unknown reference cell contaminants, such
as sulfides, may exist. The gel solution maintains its
viscosity at high temperatures, and resists the effect
of pumping and dilution, resulting in an extended
2 Rosemount Analytical
FEATURES AND APPLICATIONS
Continued from page 1
service life. A choice of a wood or ceramic liquid junction allows the user to optimize performance by
emphasizing reference life (wood) or chemical resistance (ceramic).
In many flow applications, crystalline or viscous coatings are present, such as calcium carbonate or petroleum oils, which may coat the electrode surfaces and
impede the sensor’s performance. The flow-powered
cleaning option may be used in these instances. A
specially designed flow chamber directs the process
fluid in a circular path carrying three Teflon1balls that
clean the electrode surface, physically preventing
accumulation of coating materials. Flow-powered
cleaning is suitable for all hazardous area applications.
The Model 381 is available with 3K Balco or Pt 100
temperature compensation and is compatible with all
Rosemount Analytical pH/ORP Analyzers.
1
Teflon is a registered trademark of E.I. du Pont de Nemours & Company.
SPECIFICATIONS
Materials of Construction:
Body, Cover and Flow Cell: Polyethersulfone (PES)
O-Rings: Viton
2
Measuring Electrode: Glass (and platinum or gold
for Model 381 ORP)
Liquid Junction: Kynar3/wood (Code 20) or
Kynar/ceramic (Code 21)
Solution Ground: 316 Stainless steel (Code + only)
Sensor Process Connections:
Submersion: 3/4 in. MNPT
Insertion: 2 in. MNPT
Flow Through Cell: 3/4 in. MNPT inlet and outlet
Measuring Ranges:
ORP; -1500 to +1500 mV
pH; ACCUGLASS
™
4
0-14
Minimum Conductivity: 75 μS/cm, nominal 100 μS/cm
Temperature Compensation: Automatic, 0 to 100°C
(32 to 212°F)
Maximum Pressure/Temperature Rating:
790 kPa (abs) at 100°C (100 psig at 212°F)
Cable: For Code pH, pHE, ORP: 4 conductor, 22 GA
with common shield. Code +: 10 conductor,
shielded cable
Weight/Shipping Weight: 1.0 kg/1.7 kg (2.2 lb/3.7lb)
2
Viton is a registered trademark of E.I. du Pont de Nemours & Co.
3
Kynar is a trademark of Elf Atochem North America, Inc.
4
ACCUG LASS is a trademark of Rosemount Analytical.
Percent Linearity Over pH Range
General Purpose and Ruggedized glass (codes -10 &-12) High pH glass (code -11)
0-2 pH 97% 94%
2-12 pH 99% 97%
12-13 pH 96% 98%
13-14 pH 92% 98%
* Note: Ruggedized glass electrodes are ideal for abrasive applications, but response times are typically slower than other glass
formulas.
MOUNTING AND DIMENSIONAL DRAWING
INSERTION AND FLOW THROUGH INSTALLATION
PIPE TEE
INSTALLATION
STRAIGHT
FLOW
SIDE OF TANK
INSTALLATION
PIPE TEE INSTALLATION
ELBOW FLOW
GASKET
WELD
150 LBS. RAISED
FACE FLANGE
PIPE LINE
INSTALLATION
2 IN. MNPT
2 IN. MNPT
2 IN.
MNPT
2 IN.
MNPT
3/4 IN.
MNPT
10°
MIN
FLOW
FLOW
FLOW
10°
MIN
CABLE
3/4” MNPT
COVER
BODY
2 IN. MNPT
(FOR INSERTION
INSTALLATION)
4.5 IN.
15 FT.
249.2
8-13/16
48.4
1-28/32
47.6
1-7/8 DIA
81.7
3-7/32 DIA
CORD GRIP
(DO NOT REMOVE)
MEASURING
ELECTRODE
TEMPERATURE
COMPENSATOR
1
LIQUID JUNCTION
9.5
3/8
1
ALSO SERVES AS SOLUTION GROUND FOR 381+
Rosemount Analytical 3
MILLIMETER
INCH
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