Emerson 381 User Manual
pH/ORP Sensor
Instruction Manual
PN 51-381/rev.D
October 2007
Model 381
CAUTION
SENSOR/PROCESS
APPLICATION COMPATIBILITY
The wetted sensor materials may not
be compatible with process com position and operating conditions.
Application compat ibility is entirely the
responsibility of the user.
DANGER
HAZARDOUS AREA INSTALLATION
Installations near flammable liquids or in hazardous area locations must be carefully evaluated by qualified on site safety personnel.
This sensor is not
Intrinsically Safe or
Explosion Proof.
To secure and maintain an intrinsically safe
installation, the certified safety barrier,
transmitter, and sensor combi nation must
be used. The installation system must comply with the governing approval agency (FM,
CSA or BASEEFA/CENELEC) hazardous
area classification requirements. Consult
your analyzer/transmitter instruc tion manual
for details.
Proper installation, operation and servicing
of this sensor in a Hazardous Area Instal lation is entirely the responsibility of the user.
ESSENTIAL INSTRUCTIONS
READ THIS PAGE BEFORE
PROCEEDING!
Rosemount Analytical designs, manufactures, and tests its
products to meet many national and international standards. Because these instruments are sophisticated technical products, you must properly install, use, and maintain
them to ensure they continue to operate within their normal
specifications. The following instructions must be adhered
to and integrated into your safety program when installing,
using, and maintaining Rosemount Analytical products.
Failure to follow the proper instructions may cause any one
of the following situations to occur: Loss of life; personal
injury; property damage; damage to this instrument; and
warranty invalidation.
• Read all instructions prior to installing, operating, and
servicing the product. If this Instruction Manual is not the
correct manual, telephone 1-800-654-7768 and the
requested manual will be provided. Save this Instruction
Manual for future reference.
• If you do not understand any of the instructions, contact
your Rosemount representative for clarification.
• Follow all warnings, cautions, and instructions marked on
and supplied with the product.
• Inform and educate your personnel in the proper installation, operation, and maintenance of the product.
• Install your equipment as specified in the Installation
Instructions of the appropriate Instruction Manual and
per applicable local and national codes. Connect all
products to the proper electrical and pressure sources.
• To ensure proper performance, use qualified personnel
to install, operate, update, program, and maintain the
product.
• When replacement parts are required, ensure that qualified people use replacement parts specified by
Rosemount. Unauthorized parts and procedures can
affect the product’s performance and place the safe
operation of your process at risk. Look alike substitutions
may result in fire, electrical hazards, or improper operation.
• Ensure that all equipment doors are closed and protective covers are in place, except when maintenance is
being performed by qualified persons, to prevent electrical shock and personal injury.
Emerson Process Management
Rosemount Analytical Inc.
2400 Barranca Parkway
Irvine, CA 92606 USA
Tel: (949) 757-8500
Fax: (949) 474-7250
http://www.RAuniloc.com
© Rosemount Analytical Inc. 2001
MODEL 381 pH/ORP TABLE OF CONTENTS
MODEL 381 pH/ORP SENSOR
TABLE OF CONTENTS
Section Title Page
1.0 DESCRIPTION AND SPECIFICATIONS........................................................... 1
1.1 Features and Applications................................................................................. 1
1.2 Sensor Specifications........................................................................................ 2
1.3 Ordering Information ......................................................................................... 3
2.0 INSTALLATION ................................................................................................. 5
2.1 Installation ......................................................................................................... 5
2.2 Submersion Installation (Code 02).................................................................... 5
2.3 Insertion Installation (Code 00) ......................................................................... 7
2.4 Flow Through Installation (Code 03) ................................................................. 7
2.5 Flow Powered Cleaner Installation (Code 04)................................................... 7
2.6 Wiring ................................................................................................................ 7
2.7 Start-Up and Calibration.................................................................................... 14
2.8 Model 381 pH and pHE..................................................................................... 14
2.9 Model 381 ORP................................................................................................. 14
3.0 MAINTENANCE ................................................................................................ 15
3.1 General ............................................................................................................. 15
3.2 Periodic Maintenance........................................................................................ 15
3.3 Troubleshooting................................................................................................. 16
3.4 Preamplifier Troubleshooting ............................................................................ 18
3.5 T.C. Element Maintenance................................................................................ 18
4.0 ULTRASONIC CLEANER ................................................................................. 21
4.1 Ultrasonic Cleaner............................................................................................. 21
4.2 Specifications .................................................................................................... 21
4.3 Installation ......................................................................................................... 21
4.4 Operation .......................................................................................................... 22
4.5 Maintenance...................................................................................................... 22
4.6 Replacement Parts............................................................................................ 22
5.0 RETURN OF MATERIAL................................................................................... 25
LIST OF TABLES
Table No. Title Page
2-1 ORP of Saturated Quinhydrone Solutions (in Millivolts).................................... 14
3-1 Troubleshooting................................................................................................. 17
3-2 Temperature vs. Resistance of Auto TC Element.............................................. 18
3-3 Ro& R1Values for Temperature Compensation Elements .............................. 18
3-4 Model 381 Spare Parts...................................................................................... 19
3-5 Accessories....................................................................................................... 19
i
MODEL 381 pH/ORP TABLE OF CONTENTS
MODEL 381 pH/ORP SENSOR
LIST OF FIGURES
Figure No. Title Page
1-1 Dimensional Drawing ........................................................................................ 3
1-2 Mounting Drawing ............................................................................................. 3
2-1 Model 381 Sensor Component Locator Diagram.............................................. 6
2-2 Submersion Installation Diagram ...................................................................... 8
2-3 Insertion Installation Diagram............................................................................ 8
2-4 Flow Through Installation Diagram (Code 03 or 04) ......................................... 9
2-5 Installation Details Low Flow Conditions Model 381 (Code 03-04)................... 9
2-6 Retro-Fit Kit and Code-04 Flow Powered Cleaner, Model 381 ......................... 10
2-7 Flow Through Diagram and Wiring (Code 03 or 04) ......................................... 11
2-8 Remote Junction Box with Internal Preamp...................................................... 12
2-9 Wiring with Weatherproof or Div. 2 (Code 2) Junction Box .............................. 13
4-1 Model 381 Ultrasonic Cleaner and Wiring......................................................... 23
4-2 Dimensional and Component Locator Ultrasonic Generator............................. 24
ii
About This Document
This manual contains instructions for installation and operation of the Model 381
pH/ORP Sensor.
The following list provides notes concerning all revisions of this document.
Rev. Level
Date Notes
A 6/94-1/00 This is the initial release of the product manual. The manual
has been reformatted to reflect the Emerson documentation
style and updated to reflect any changes in the product offering.
B 5/02 Updated multiple drawings throughout manual.
C 3/05 Updates
D 10/07 Updated page 3 code 00 insertion is no longer available.
1
• 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 performance, extended service life, and resists the effects of pumping, dilution and contamination.
• OPTIONAL FLOW-POWERED OR ULTRASONIC CLEANING provides trouble-free service in difficult applications.
1.1 FEATURES AND APPLICATIONS
The Model 381 Sensor measures the pH or the
Oxidation Reduction Potential (ORP) of aqueous solutions in pipelines, open tanks or ponds. The sensor is
used in most industrial applications including SO
2
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 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 amplifies the high impedance 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 temperatures 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 sulfides, 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 coatings, such as calcium carbonate or petroleum oils,
may coat the electrode surfaces and impede the sensor'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 Teflon1balls 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 hazardous 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 compensator order the Model 381 pHE.
MODEL 381 pH/ORP SECTION 1.0
DESCRIPTION AND SPECIFICATIONS
SECTION 1.0
DESCRIPTION AND SPECIFICATIONS
1
Teflon is a registered trademark of E.I. du Pont de Nemours & Co.
2
MODEL 381 pH/ORP SECTION 1.0
DESCRIPTION AND SPECIFICATIONS
1.2 SENSOR SPECIFICATIONS
Materials of Construction:
Body, Cover and Flow Cell: Polyethersulfone (PES).
O-Rings: Viton
2.
Measuring Electrode: Glass (and platinum for
Model 381 ORP).
Liquid Junction: Kynar3/wood (Code 20) or
Kynar/ceramic (Code 21).
Process Connections: Submersion: 3/4 inch MNPT.
Insertion: 2 inch MNPT.
Flow Through:3/4 inch MNPT.
Dimensions: (see Figure 1-1).
Measuring Range: pH 0-14
ORP –1500mV to +1500mV
Temperature Compensation: (Model 381 pH only,
not required for Model 381 ORP).
Automatic, 0 to 100°C (32 to 212°F).
Pressure Rating: 790 kPa abs at 100°C
(100 psig at 212°F)
Cable: Four-conductor, 22 GA, each (0.64 mm dia.),
with common shield.
Weight/Shipping Weight: 1.0 kg/1.7 kg (2.2 lb./ 3.7 lb.).
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.
HANDRAIL MOUNTING ACCESSORY HANDRAIL MOUNTING ACCESSORY
FIGURE 1-2. Mounting Drawing
FIGURE 1-1. Dimensional Drawing
PN 1000856 PN 11275-00
3
1.3 ORDERING INFORMATION Model pH/ORP Sensor is housed in a PES body suitable for insertion, submer-
sion or flow through installation. The sensor includes an integral preamplifier, measuring electrode, double junction gel-filled reference cell, automatic temperature compensation for pH, and a choice of two cable lengths of
either 15 ft. or 50 ft. (4.5 or 15.2 m).
MODEL 381 INSERTION, SUBMERSION, FLOW THROUGH SENSOR
CODE FUNCTION
pH Requires Code 30
ORP Requires Code 32 (not for use with 1054/1054A ORP Series)
pHE Requires Code 31 (for use with 1054/1054A/2054 Series and 2081)
381 pH 00 10 20 30 40 51 EXAMPLE
MODEL 381 pH/ORP SECTION 1.0
DESCRIPTION AND SPECIFICATIONS
CODE MEASURING ELECTRODE
10 General purpose pH
11 High pH Electrode, requires Code 21. For sodium concentrations greater than 1% or
continuous measurement above 11 pH.
12 Ruggedized pH Electrode. For abrasive solutions.
13 Platinum ORP Electrode.
14 Gold ORP Electrode.
15 HF pH Electrode. For HF concentrations less than 100 ppm.
CODE LIQUID JUNCTION
20 Wood/KYNAR Liquid Junction
21 Ceramic/KYNAR Liquid Junction
CODE CABLE
40 15 ft. cable for integral sensor preamp
41
15 ft. coax cable w/BNC connector for remote sensor preamp
and integral analyzer preamp (1054A-54/2054-54 only)
42 15 ft. coax cable w/o BNC connector for integral analyzer
preamp (1054, 1181-43/44 & 2081-05 only)
43 50 ft. cable for integral sensor preamp
CODE INTEGRAL PREAMPLIFIER
50 Preamp for Models 1181 pH/ORP & 1050/1060
51 Preamp for Models 1003/1023
52 Preamp NOT REQUIRED
54
Preamp for Models 1054/2054 Series, and 2081
CODE TEMPERATURE COMPENSATION
30 Automatic T.C., 3.0K ohm. For Models 1003, 1050 & 1181 pH
31
Automatic T.C., PT-100. For Models 1054/2054 Series, and 2081
32
Automatic T.C., NOT REQUIRED (For Models 1023, 1060 and 1181 ORP)
CODE INSTALLATION
02 Submersion
03 Flow Through
04 Flow Through with Flow Powered Cleaner (not available with ORP)
4
5
MODEL 381pH/ORP SECTION 2.0
INSTALLATION
SECTION 2.0
INSTALLATION
2.1 INSTALLATION. Prepare the sensor for instal lation
as follows (see Figure 2-1):
1. Remove the cover from the body by grasping the
body and rotating the cover 1/4 turn counterclockwise.
2. When the cover breaks loose from the body, pull
the cover straight out.
3. Lubricate the seals of the glass electrode with Oring lubricant, Rosemount Analytical P/N
2001928, and install the glass electrode in the
body. Tighten the electrode nut by hand. DO NOT
use tools.
CAUTION
Do not get lubricant on amber tip of glass
electrode. It will disrupt the electrical circuit
path.
4. Make sure the double junction electrode is thread-
ed tightly.
5. Plug the preamplifier (or remote connector) onto
the T.C. and reference electrode pins.
6. Connect the BNC connector from the glass elec-
trode to the preamplifier.
7. Install the body O-rings. Make sure they are clean,
and not twisted. Make sure the covers mating surfaces faces are clean.
NOTE
Both body O-rings must be installed and
lubricated to ensure a water tight seal.
Failure to seal the body properly will result
in water damage, in insertion applications.
8. Lubricate the body O-rings with O-ring lubricant,
P/N 2001928.
9. Plug the cable connector to the preamplifier, mak-
ing sure the cable is toward the center of the body.
10. Install the cover on the body so that the threads
will engage.
11. Rotate the cover until the triangle on the body
aligns with (or falls within) the adjacent mark on
the cover.
IMPORTANT!
12. While holding the sensor in an up side down position (see Figure 2-1), remove the 1/4 inch plug
from the electrode tip end of the sensor.
13. Install the liquid junction in place of the 1/4 inch
plug, using Teflon tape on the liquid junction
threads.
CAUTION
DO NOT use pipe joint compound or pipe
dope on the threads of the liquid junction.
The electrical circuit will be disrupted if the
liquid junction is contaminated.
2.2 SUBMERSION INSTALLATION (Code 02). To
install the sensor in process proceed as follows (see
Figure 2-2):
1. Wrap Teflon tape on 3/4 inch MNPT threads of
cover and on standpipe threads. Seal must be
water tight. Cable gland is not waterproof. Do not
allow water to accumulate in the stand pipe.
CAUTION
Do not use a pipe wrench on the plastic
parts. Severe damage could result.
2. Attach a 3/14 inch coupling to the sensor.
3. Attach electrode shroud to 2 inch MNPT.
4. Feed cable through the rigid standpipe.
5. Attach the rigid standpipe to 1 inch coupling.
CAUTION
Rigid stand pipe must be water-tight; cable
seal is not waterproof.
6. Tighten all fittings and secure the standpipe to
minimize sensor movement. Use flexible conduit
at the top of the rigid standpipe to permit removal
of the sensor for periodic maintenance.
7. Refer to Section 2.6 and wire the sensor to the
transmitter as described.
6
MODEL 381pH/ORP SECTION 2.0
INSTALLATION
FIGURE 2-1. Model 381 Sensor Component Locator Diagram
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