Rosemount™ 389/389VP
General Purpose pH/ORP Sensors
Instruction Manual
LIQ-MAN-389, Rev G
July 2017
Essential instructions
Read this page before proceeding!
Emerson designs, manufactures, and tests its Rosemount 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 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 this product. If this instruction manual is not the correct
manual, call 1-855-724-2638, and we will provide the requested manual. Save this manual for future reference.
• If you do not understand any of the instructions, contact your Emerson 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 manual and per applicable local and
national codes. Connect all products to the proper electrical and pressure sources.
• Install your equipment as specified in the Installation section 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 people, to prevent electrical shock and personal injury.
WARNING!
HAZARDOUS AREA INSTALLATION
Installations near flammable liquids or in hazardous area locations must be carefully evaluated by qualified on site safety personnel.
To secure and maintain intrinsically safe installation, an approprieate transmitter/safety barrier/sensor combination must be used.
The installation system must be in accordance with the governing approval agency (FM, CSA, or BASEEFA/CENELEC) hazardous are
classification requirements. Consult your analyzer/transmitter instruction manual for details.
Proper installation, operation, and servicing of this sensor in a hazardous area installation are entirely your responsibility.
WARNING!
SENSOR/PROCESS APPLICATION COMPATIBILITY
The wetted sensor materials may not be compatible with process composition and operating conditions. Application compatibility is
entirely your responsibility.
CAUTION!
If a 275, 375, or 475 Universal HART Communicator is used with these transmitters, the software within the 275, 375, or 475 may
require modification. If a software modification is required, please contact your local Rosemount Service group or National Response
Center at 1-800-654-7768.
About this Document
This manual contains instructions for installation and operation of the Rosemount
389/389VP General Purpose pH/ORP Sensors. The following list provides notes concerning
all revisions of this document.
Rev. level Date Notes
A 2/2001 This is the intial 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.
Rev. level Date Notes
B 2/2002 Added 1055 wiring diagrams.
C 10/2005 Changed PN 933022 to PN 9320057 on the drawing 400389VP12, page 5 and Table 5-2,
page 17.
D 12/2008 Updated to add VP.
E 03/2012 Updated pages 23 and 26.
F 1/2013 Incorporated SMART Sensor technology.
G 4/2017 Updated wiring diagrams. Reformatted to reflect new Emerson branding guidelines.
Contents
Contents
Chapter 1 Description and specifications ..........................................................................................1
1.1 Features and applications ...............................................................................................................1
1.2 Specifications .................................................................................................................................2
1.3 Certifications ..................................................................................................................................3
1.4 Ordering Information ..................................................................................................................... 4
Chapter 2 Installation .......................................................................................................................7
2.1 Unpacking and Inspection .............................................................................................................. 7
2.2 Mounting ....................................................................................................................................... 7
2.2.1 Submersion mounting .....................................................................................................9
2.2.2 Flow Through and Insertion Mounting ...........................................................................11
2.3 Electrical Installation .................................................................................................................... 11
Chapter 3 Calibration and maintenance .........................................................................................23
3.1 Sensor Preparation .......................................................................................................................23
3.2 Rosemount 389/389VP pH Calibration .........................................................................................23
3.2.1 Recommended Two Point Buffer Calibration Procedure ................................................ 23
3.2.2 Recommended pH Sensor Standardization ....................................................................24
3.3 Rosemount 389/389VP ORP Calibration .......................................................................................24
3.3.1 Calibration .....................................................................................................................24
Chapter 4 Maintenance .................................................................................................................. 27
4.1 Electrode Cleaning ....................................................................................................................... 27
4.2 Automatic Temperature Compensator ........................................................................................ 27
4.3 ORP ..............................................................................................................................................28
4.3.1 Platinum Electrode Check ..............................................................................................28
4.3.2 Cleaning Platinum Electrode ..........................................................................................29
Chapter 5 Troubleshooting ............................................................................................................ 31
Chapter 6 Return of Material .......................................................................................................... 33
Chapter 7 EC Declaration of Conformity ......................................................................................... 35
Chapter 8 Intrinsically Safe Sensor Installation Drawing - FM ..........................................................37
Instruction Manual i
Contents
ii 389/389VP
Description and specifications
1 Description and specifications
1.1 Features and applications
Rosemount 389VP triple-junction sensors are offered with SMART capabilities. SMART
options are enabled when used with Rosemount 1056, 1057, 1066, and 56 transmitters.
The pH-loop capabilities include auto-recognition of the SMART sensor, automatic upload
of calibration data and associated time stamp, and historical recording of pH diagnostics
(slope, offset, reference impedance, and glass impedance). This trending data allows
technicians to predict frequency of maintenance and estimate sensor life for a particular
process condition. Additional SMART features include factory calibration, resetting SMART
sensor calibration data with user menus without power cycling, and manufacturing
information.
The reference junction aids in the sensor's resistance to poisoning ions and helps prolong
sensor life. Rosemount 389/389VP sensors have a triple junction reference, which protects
the reference element from poisoning ions - such as ammonia, chlorine, cyanides, and
sulfides - in the process. Both models are made with anouter ceramic junction constructed
in an annualr design around the pH/ORP sensitive membrane.
The AccuGLASS™ pH glass formulations exceed industry standards. The AccuGlass pH glass
is a result of many years of glass research resulting in a formulation which has been found
to increase the life of the sensor. Unlike other pH glasses presently on the market, this
glass resists cracking, especially at higher temperatures, and reduces sodium ion errors
commonly found in high pH applications. Overall, the AccuGlass formulation enhances the
sensor performance to measure pH more accurately and have a longer sensor life than
ever before.
A choice of pH glass electrodes is available to best meet various application needs. Two
types are available: general purpose and high pH glass. The AccuGlass hemi bulb is the
standard glass offered on both types and can be used for most applications.
The Rosemount 389VP is configured with a Variopol (VP8) sensor-to-cable connector
which eliminates re-wiring and cable twisting when replacing sensors. The Variopol VP8
multiple pin connector option uses a mating VP cable. Once the cable is installed and wired
to the transmitter, sensors are easily replaced without replacing the cable and without
rewiring the transmitter. Also, the cable can be disconnected from the sensor before
removal from the process which eliminates cable twisting. VP8 cable assemblies work with
both VP8 and VP6 sensor connectors.
The Rosemount 389/389VP has a molded Tefzel body with Viton O-rings, making each
sensor very robust and chemically resistant. Complete encapsulation eliminates leakage or
high humidity problems traditionally found in other pH/ORP designs. The seimplified
construction, designed with user convenience in mind, does not require electrolyte (KCl)
replenishment or any high maintenance troubleshooting procedures.
Instruction Manual 1
Description and specifications
Rosemount 389/389VP sensors are combintation sensors (pH, reference, and temperature
within sensor body) and measure pH or ORP (oxidation/reduction potential) of aqueous
solutions in pipelines, open tanks, or ponds. rosemount 389/389VP sensors are suitable for
virtually all applications and are compatible with Rosemount and other manufacturers'
instruments.
Installation is easily achieved through the wide variety of mounting configurations. These
sensors feature a 1 inch (MNPT) front and rear facing connections for insertion,
submersion, or flow-through pH and ORP applications.
1.2 Specifications
Percent linearity over pH rangeTable 1-1:
pH range GPLR glass (-10) High pH glass (-11)
0 to 2 pH 94% 94%
2 to 12 pH 99% 97%
12 to 13 pH 97% 98%
13 to 14 pH 92% 98%
Rosemount 389/389VP pH/ORP sensor specificationsTable 1-2:
Measurement range
pH 0 to 14
ORP -1500 to +1500 mV
Temperature range
32 to 185 °F (0 to 85 °C)
Automatic temperature compensation : 32 to 185 °F (0 to 85 °C)
Maximum pressure
100 psig (790 kPa[abs]) at 150 °F (65 °C) - see Figure 1-1
Materials of construction
Sensor body Tefzel
pH electrode Glass
ORP electrode Platinum
Junction Ceramic
O-ring Viton
Process connections
Front facing 1 in. MNPT
Rear facing 1 in. MNPT
2 389/389VP
Description and specifications
Rosemount 389/389VP pH/ORP sensor specifications (continued)Table 1-2:
Cable
389 Integral preamplifier - 25 ft (7.8 m); no preamplifier - 15 ft
(4.6 m)
389VP Use 24281-XX, 2.5 ft (0.8 m) to 100 ft (31 m) (see Accesso-
ries)
Weight/shipping weight
1 lb / 2 lb (0.45 kg / 0.9 kg)
Pressure/temperature operating range for Rosemount 389/389VPFigure 1-1:
1.3 Certifications
IECEx
Sensors without preamp (pH and ORP) -Ex ia IIC T4 Ga (-20 ºC ≤ Ta ≤ +60 ºC)
Sensors with SMART preamp (pH only) - Ex ia IIC T4 Ga (-20 ºC ≤ Ta ≤ +60 ºC)
Sensors with standard preamp (ORP only) - Ex ia IIC T4 Ga (-20 ºC ≤ Ta ≤ +80 ºC) or Ex IIC T5
Ga (-20 ºC ≤ Ta ≤ +40 ºC)
Per standards IEC60079-0: 2011, IEC 60079-11: 2011
ATEX
Sensors without preamp (pH and ORP)- II 1 G Ex ia IIC T4 Ga (-20 ºC ≤ Ta ≤ +60 ºC)
Instruction Manual 3
Description and specifications
Sensors with SMART preamp (pH only) - II 1 G Ex ia IIC T4 Ga (-20 ºC ≤ Ta ≤ +60 ºC)
Sensors with standard preamp (ORP only) - II 1 G Ex ia IIC T4 Ga (-20 ºC ≤ Ta ≤ +80 ºC) or II 1
G Ex ia IIC T5 Ga (-20 ºC ≤ Ta ≤ +40 ºC)
Per standards EN 60079-0:2012 + A11:2013, EN 60079-11:2012
FM
See online FM Certificate of Compliance for applicable sensor options:
Intrinsically safe for use in Class I, II, and III, Division 1, Groups A, B, C, D, E, F, and G;
Temperature Class T6 Ta = -20 °C to + 60 °C
Intrinsically safe for use in Class I, Zone 0, AEx ia IIC T6 Ta = -20 °C to + 60 °C
Nonincendive for use in Class I, Division 2, Groups A, B, C, and D; Temperature Class T6 Ta
= -20 °C to + 60 °C
Suitable for use in Class II and III, Division 2, Groups E, F, and G; Temperature Class Ta =
-20 °C to + 60 °C Hazardous (Classified) Locations
IS/I, II, III/1/ABCDEFG/T6 Ta = 60 °C - 140332; Entity: I/0/AEX ia IIC/T6 Ta =60 °C - 1400332;
Entity; NI/I/2/ABCD/T6 Ta = 60 °C; S/I, III/2/EFG/T6 Ta = 60 °C; Entity Parameters
Per standards 3600: 1998; 3610: 2010, 3611:2004, 3810:2005
CSA
See online CSA Certificate of Compliance for applicable sensor options:
Intrinsically Safe: Class I, Division 1, Groups ABCD; Class II, Division 1, Groups EFG; Class III,
Class I, Division II, Groups ABCD; Ambient temperature rating -20 °C to + 60 °C; Ex ia IIC; T6
Intrinsically Safe and Non-Incendive: Class I, Division 1, Groups ABCD; Class II, Division 1,
Groups EFG; Class III; Class 1, Division 2, Groups ABCD; Ex ia IIC; T6; Ambient temperature
rating -20 °C to + 60 °C: (Simple Apparatus)
Per standards C22.2 No. 144 -M1987, C22.2 No 157 - M1992, CAN/CSA E60079:0:07,
CAN/CSA E60079:11:02, UL 50, UL 508, UL 913, UL 60079-0:2005, UL 60079-11: 2002
1.4 Ordering Information
The Rosemount 389 and 389VP General Purpose pH/ORP Sensors are housed in a molded
Tefzel body with 1 in. MNPT forward and rear facing threads suitable for insertion,
submersion, or flow through installation. The sensors can be configured with a general
purpose pH, high pH, or platinum ORP electrode. Rosemount 389VP sensors are offered
with SMART preamplifiers for pH measurements and standard integral preamplifiers for
ORP measurements. These sensors may be configured without a preamplifier, but must be
used with a remote preamplifier (j-box or transmitter). Automatic temperature
compensation is standard. Sensors are available with either an integral cable connection
(389) or Variopol (VP6) connector (389VP). Variopol cables sold separately (see Table 5-2).
4 389/389VP
Description and specifications
Rosemount 389 pH/ORP Sensor ordering informationTable 1-3:
Model Sensor type
389 pH/ORP Sensor
Preamplifier/cable
01 Integral pramplifier, 25 ft cable
02 No preamplifier, 15 ft cable
Combination electrode
10 pH -GPLR glass
11 pH-high pH glass
12 ORP
Transmitter/TC compatibility
50 1181, 1050, 1060 (code -01 or -02)
54 1054A/B, 81, 2081, (code -01 or -02); for 54, 56, 1055, 1056, 1057, 1066, 5081, 6081, and XMT
(code -02 only)
55 54, 56, 1055, 1056, 1057, 5081, 6081, and XMT (code -01 only)
(1)
Optional
- No selection
62 Cable without BNC for models: 54, 56, 1055, 1056, 1057, 1066, 5081, 6081, and XMT (codes -02 and
-54 only)
Typical model number: 389-02-10-54-62
(1) Preamplifier is SMART if selected with pH electrode and option 55 only. Preamplifier is standard for ORP electrodes and for options 50
and 54.
Instruction Manual 5
Description and specifications
Rosemount 389VP pH/ORP Sensor ordering informationTable 1-4:
Model Sensor type
389VP pH/ORP sensor
Combination electrode
10 pH - GPLR glass
11 pH - high pH glass
12 ORP
Transmitter/TC compatiblity
50 1181, 1050, 1060 (code -01 or -02)
54 1054A/B, 81, 2081 (code -01 or -02); for 54, 56, 1055, 1056, 1057, 1066, 5081, 6081, and XMT
(code -02 only)
55 54, 56, 1055, 1056, 1057, 5081, 6081, and XMT (code -01 only)
Preamplifier option
- No preamplifier
70 SMART preamplifier
(1)
Typical model number: 389VP-10-55-70
(1) Only available with -10, -11, and -55 options.
6 389/389VP
2 Installation
2.1 Unpacking and Inspection
1. Inspect the outside of the carton for any damage.
2. If damage is detected, contact the carrier immediately.
3. Inspect the hardware.
4. Make sure all the items in the packing list are present and in good condition.
5. Notify the factory if any part is missing.
2.2 Mounting
The sensor has been designed to be located in industrial process environments.
Temperature and pressure limitations must not be exceeded at any time. A Caution label
regarding this matter is attached to the sensor with the cable. Please do not remove this
label..
Installation
Rosemount 389 Sensor dimensional drawingFigure 2-1:
Instruction Manual 7
Installation
Rosemount 389VP Sensor dimensional drawingFigure 2-2:
8 389/389VP
Installation
WARNING!
IRRITANT
Internal electrolyte fill may cause skin or eye irritation.
Mounting guidelines
1. Shake down the sensor to remove any air bubbles that may be present inside the tip
of the pH glass.
2. Do not install the sensor horizontally. The sensor must be 10 º off the horizontal to
ensure accuracy.
3. Do not install the sensor upside down.
4. With the standard recessed electrode, air bubbles may become trapped in the
sensor end. This problem is most commonly encountered in areas of low flow or
during calibration. Shake the probe while it is immersed in solution to remove
bubbles.
In most cases, the sensor can simply be installed as shipped, and you can obtain readings
with an accuracy of ±0.2 pH. To obtain greater accuracy or to verify proper operation, the
sensor must be calibrated as a loop with its compatible analyzer or transmitter.
2.2.1 Submersion mounting
Rosemount 389 and 389VP sensors have a 1 in. MNPT process connection at the back of
the sensor.
1. Using a standard 1 in. union, mount the sensor to a 1 in. SCH 80 CPVC or PVDF
standpipe.
2. Tapered pipe threads in plastic tend to loosen after installation. We therefore
recommend that you use Teflon tape on the threads and check the tightness of the
connection frequently to ensure that no loosening has occurred.
3. To prevent rain water or condensation from running into the sensor, use a
weatherproof junction box (see Figure 2-3).
Instruction Manual 9
Installation
Submersion installationsFigure 2-3:
4. Run the sensor cable through a protective conduit for isolation from electrical
interference or physical abuse from the process.
5.
Install the sensor within 80 ° of vertical, with the electrode facing down.
Do not run the sensor's cable with power or control wiring.
10 389/389VP
2.2.2 Flow Through and Insertion Mounting
Rosemount 389 and 389VP sensors also have a 1 in. MNPT process at the front of the
sensor for mounting into a 1-1/4 in. tee or the process. See Figure for installation
configurations.
Flow Through and Insertion InstallationsFigure 2-4:
Installation
Note
Valves and fittings by others. Mount the sensor at least 10 ° from horizontal.
Note
Do not use large pipe wrenches to tighten the sensor into a flange or other type of mounting.
2.3 Electrical Installation
Figure 2-5 through Figure 2-19 provide the guidelines for wiring Rosemount 389/389VP
sensors to various Rosemount transmitters.
1.
If the cable needs to be extended, use a high quality four conductor shielded
instrument cable available from Rosemount.
Note
If the cable is too long, loop up the excess cable. If the cable has to be shortened, splice and
terminate each conductor neatly and make sure that the overall (outermost) drain wire is not
shorted out with either of the two inner drain wires (shields).
2. Signal cable should be run in a dedicated conduit (preferably an earth grounded
metallic conduit) and should be kept away from AC power lines. For your
convenience, a spade lug kit is furnished (in a plastic bag wrapped around the cable).
Instruction Manual 11
Installation
Model 389 with Insertion Mounting Adapter P/N 23242-02Figure 2-5:
VP 8 Cable, Rosemount 389VP Sensor EndFigure 2-6:
12 389/389VP
Installation
VP8 Cable, Instrument EndFigure 2-7:
NOTICE
For additional wiring information on this product, including sensor combinations not shown
here, please refer to the Liquid Transmitter Wiring Diagrams.
Instruction Manual 13
Installation
Figure 2-8:
Rosemount 389-01-xx-55 Wiring to Rosemount 1056, 1057, and 56
Transmitters
14 389/389VP
Installation
Rosemount 389-01-xx-55 Wiring to Rosemount 1066 TransmitterFigure 2-9:
Rosemount 389-01-xx-55 Wiring to Rosemount 5091 TransmitterFigure 2-10:
Instruction Manual 15
Installation
Figure 2-11:
Rosemount 389VP Wiring to Rosemount 1056, 1057, and 56
Transmitters
16 389/389VP
Installation
Rosemount 389VP Wiring to Rosemount 1066 TransmitterFigure 2-12:
Rosemount 389VP Wiring to Rosemount 5081 TransmitterFigure 2-13:
Instruction Manual 17
Installation
Figure 2-14:
Rosemount 389VP-xx-55-70 Wiring to Rosemount 1056, 1057, and 56
Transmitters
Rosemount 389VP-xx-55-70 Wiring to Rosemount 1066 TransmitterFigure 2-15:
18 389/389VP
Installation
Rosemount 389VP-xx-55-70 Wiring to Rosemount 5081 TransmitterFigure 2-16:
Instruction Manual 19
Installation
Figure 2-17:
Rosemount 389-02-xx-54-62 Wiring to Rosemount 1056, 56, and 1057
Transmitters
20 389/389VP
Installation
Rosemount 389-02-xx-54-62 Wiring to Rosemount 1066 TransmitterFigure 2-18:
Rosemount 389-02-xx-54-62 Wiring to Rosemount 5081 TransmitterFigure 2-19:
Instruction Manual 21
Installation
22 389/389VP
Calibration and maintenance
3 Calibration and maintenance
3.1 Sensor Preparation
1. Shake down the sensor to remove any air bubbles that may be present at the tip of
the pH glass bulb.
2. In most cases, the pH sensor can simply be installed as shipped, and you can obtain
readings with an accuracy of ±0.2 pH. To obtain greater accuracy or to verify proper
operation, calibrate the sensor as a loop with its compatible transmitter.
3.2 Rosemount 389/389VP pH Calibration
1. After a temporary connection is established between the sensor and the instrument,
you may perform a buffer calibration.
2. Consult the appropriate pH/ORP transmitter instruction manual for specific
calibration and standardization procedures, or see below for the recommended two
point buffer calibration procedure.
3.2.1 Recommended Two Point Buffer Calibration Procedure
Prerequisites
Select two stable buffer solutions, preferably pH 4.0 and 7.0. (pH buffers other than pH 4.0
and pH 7.0 can be used as long as the pH values are at least two pH units apart.
Note
A pH 7 buffer solution reads an mV value of approximately zero, and pH buffers read approximately
±59.1 mV for each pH unit above or below pH 7. Check the pH buffer manufacturer specifications for
millivolt values at various temperatures, as it may affect the actual value of the buffer solution
mV/pH value.
Procedure
1.
Immerse the sensor in the first buffer solution. Allow the sensor to adjust to the
buffer temperature (to avoid errors due to temperature differences between the
buffer solution and sensor temperature) and wait for readings to stabilize.
The value of the buffer can now be acknowledged by the transmitter.
2. Once the first buffer has been acknowledged by the transmitter, rinse the buffer
solution off the sensor with distilled or deionized water.
3. Repeat steps 1 and 2 using the second buffer solution.
Instruction Manual 23
Calibration and maintenance
Once the transmitter has acknowledged both buffer solutions, a sensor slope
(mV/pH) is established (the slope value can be found within the transmitter). The
slope value should read about 59.1 mV/pH for a new sensor and will decrease over
time to approximately 47 -49 mV/pH. Once the slope reads below the 47-49 mV/pH
range, install a new sensor to maintain accurate readings.
3.2.2 Recommended pH Sensor Standardization
For maximum accuracy, the sensor can be standardized in-line or with a process grab
sample after a buffer calibration has been performed and the sensor has been conditioned
to the process. Standardization accounts for the sensor junction potential and other
interferences. Standardization does not change the sensor's slope, but simply adjusts
transmitter's reading to match that of a known process pH.
1. While obtaining a process solution sample (we recommend that you take the
sample close to the sensor), record the pH value that is shown on the transmitter
display.
2. Measure and record the pH of the process solution sample with another
temperature compensated, calibrated pH instrument. For best results, perform
standardization at the process temperature.
3. Adjust the transmitter to the standardized value.
3.3 Rosemount 389/389VP ORP Calibration
Most industrial applications have a number of ORP reactions occuring in sequence or
simultaneously. There can be several components that are oxidized or reduced by the
reagents that are used. Theoretically, the ORP potential is absolute, because it is the result
of the oxidation/reduction equilibrium. However, the actual measured potential is
dependent on many factors, including the condition of the surface of the ORP platinum
electrode. Therefore the sensor should be allowed 1-2 hours to become conditioned to the
stream when first set up or after being cleaned.
3.3.1 Calibration
WARNING!
CORROSIVE SUBSTANCE
The solution used during the following check is an acid and should be handled with care.
Follow the directions of the acid manufacturer. Wear the proper protective equipment. Do not
let the solution come in contact with skin or clothing. If contact with skin is made, immediately
rinse with clean water.
Procedure
1. Make a temporary electrical connection between the sensor and the instrument.
2. Obtain a standard solution of saturated quinhydrone (PN R508-16OZ). To make this
solution, add a few crystals of quinhydrone to either pH 4 or pH 7 buffer.
24 389/389VP
Calibration and maintenance
Quinhydrone is only slightly soluble, but only a few crystals are required (refer to
Section for an alternate ORP standard solution).
3. Immerse the sensor in the standard solution. Allow 1-2 minutes for the ORP sensor
to stabilize.
4. Adjust the standardized control of the transmitter to the solution value shown in
Table 3-1.
The resulting potentials, measured with a clean platinum electrode and saturated
KCl/AgCL reference electrode, should be within ±20 millivolts of the value shown in
Table 3-1. Note solution temperature to ensure accurate interpretation of results.
The ORP value of saturated quinhydrone solution is not stable over long periods of
time. Therefore, make these standards fresh each time they are used.
ORP of Saturated Quinhydrone Solution (millivolts)Table 3-1:
pH 4 Solution pH 7 Solution
Temp ºC 20 25 30 20 25 30
mV Potential
268 264 260 94 87 80
5. Remove the sensor from the buffer, rinse, and install in the process.
Instruction Manual 25
Calibration and maintenance
26 389/389VP
4 Maintenance
Rosemount 389/389VP sensors require minimum maintenance. Keep the sensors clean
and free of debris and sediment at all times. The frequency of cleaning by wiping or
brushing with a soft cloth or brush is determined by the nature of the solution being
measured. Remove sensors from the process periodically and check them in buffer
solutions.
WARNING!
PRESSURE AND TEMPERATURE
Before removing the sensor, be absolutely certain that the process pressure is reduced to 0
psig and the process temperature is lowered to a safe level!
If the sensor will not calibrate, refer to your transmitter manual for proper test procedures.
If you determine that the sensor has failed, discard and replace it.
Maintenance
4.1 Electrode Cleaning
If the electrode is coated or dirty, clean as follows:
1. Remove the sensor from process.
2. Wipe the glass bulb with a soft, clean, lint free cloth or tissue. If this does not remove
the dirt or coating, go to Step 3 (detergents clean oil and grease; acids remove
scale.)
3. Wash the glass bulb in a strong detergent solution and rinse it in clean water. If this
does not clean the glass bulb, go to Step 4.
WARNING!
CORROSIVE SUBSTANCE
The solution used during the following test is an acid and should be handled with care.
Follow the directions of the acid manufacturer. Wear the proper protective equipment.
Do not let the solution come in contact with skin or clothing. If contact with skin is
made, immediately rinse with clean water.
4. Wash the bulb in a dilute 5% hydrochloric acid solution and rinse with clean water.
Soaking the sensor overnight in the acid solution can improve cleaning action.
Replace the sensor if it cannot be cleaned.
4.2 Automatic Temperature Compensator
The temperature compensator element is a temperature sensitive resistor and can be
checked with an ohmeter. Resistance increases with temperature.
Instruction Manual 27
Maintenance
The 3K element reads 3000 ohms ±1% at 77 °F (25 °C), and a Pt100 reads 110 ohms.
Resistance varies with temperature for a 3K and Pt-100 element and can be determined
according to Table or the following formula:
RT = RO [1 + R1(T-20)
Where RT = Resistance and T = Temperature in °C
Refer to Table 4-1 for RO and R1 values.
RO and R1 Values for Temperature Compensation ElementsTable 4-1:
Temperature Compensation
Element R
3K 2934 .0045
PT-100 107.7 .00385
O
R
1
Temperature vs. Resistance of Auto T.C. ElementsTable 4-2:
Temperatre °C Resistance (Ohms) ±1%
0 26270 100.0
10 2802 103.8
20 2934 107.7
25 3000 109.6
30 3066 111.5
40 3198 115.4
50 3330 119.2
60 3462 123.1
70 3594 126.9
80 3726 138.5
90 3858 134.6
100 3990 138.5
4.3 ORP
3K PT-100
4.3.1 Platinum Electrode Check
The platinum electrode may be checked as follows. There are two types of standard
solutions which may be used to check the ORP electrode/transmitter system.
Type 1: One type of commonly used ORP standard solution is the saturated quinhydrone
solution (PN R508-16OZ). Refer to Section 3.3.
28 389/389VP
Maintenance
WARNING!
CORROSIVE SUBSTANCE
The solution used during the following check is an acid and should be handled with care.
Follow the manufacturer's directions. Wear the proper protective equipment. If contact with
skin or clothing is made, immediately rinse with plenty of clean water.
Type 2: A second ORP standard solution can be prepared from the following recipe:
Procedure
1. Dissolve 39.2 grams of reagent grade ferrous ammonium sulfate, Fe(NH4)2(SO4)2 ●
6H2O and 48.2 grams of reagent grade ferric ammonium sulfate, FeNH4(SO4)2 ● 12
H2O in approximately 700 ml of water (distilled water is preferred but tap water is
acceptable).
2. Slowly and carefully add 56.2 ml of concentrated sulfuric acid.
3. Add sufficient water to bring the total solution volume up to 1000 ml.
This standard ORP solution, although not as simple to prepare as the quinhydrone recipe,
is much more stable and will maintain its millivolt value for approximately one year when
stored in glass containers. This solution (ferric/ferrous ammonium sulfate) produces a
nominal ORO of 476 +20 mV at 25 ºC when used with a saturated KCL/AgCl reference
electrode and platinum measuring electrode. Some tolerance in mV values is to be
expected due to the rather large liquid reference junction potentials that can arise when
measuring this strongly acidic and concentrated solution. However, if measuring
electrodes are kept clean and in good operating condition, consistently repeatable
calibrations can be carried out using this standard solution.
4.3.2 Cleaning Platinum Electrode
To restore the electrode to normal operation, clean the platinum electrode with baking
soda. Polish it by rubbing it with a damp paper towel and baking soda until a bright, shiny
appearance is attained.
Instruction Manual 29
Maintenance
30 389/389VP
5 Troubleshooting
TroubleshootingTable 5-1:
Trouble Probable Cause Remedy
Meter reads off scale (Display reads
overrange).
Display reads between 3 and 6 pH regardless of actual pH of solution or
sample.
Meter or display indication swings or
jumps widely in AUTO T.C. Mode.
Span between buffers extremely short
in AUTO T.C. Mode.
Sluggish or slow meter indication for
real changes in pH level.
Transmitter cannot be standardized. Electrode coated or cracked. Clean sensor as instructed in
Transmitter short spans between two
different buffer values.
Defective preamplifier. Replace preamplifier (for code 02 sen-
sors). For code 01, replace sensor.
T.C. element shorted Check T.C. element as instructed in
Section 4.2 and replace sensor if defec-
tive.
Sensor not in process or sample
stream is low.
Open glass electrode. Replace sensor.
Reference element open - no contact. Replace sensor.
Electrode cracked. Replace sensor.
T.C. element shorted. Check T.Cl. element as instructed in
T.C. element shorted. Check T.Cl. element as instructed in
Electrode cracked. Clean sensor as instructed in
Electrode defective. Replace sensor.
Defective preamplifier Replace preamplifier.
Old glass electrode or high temperature exposure.
Coated glass. Clean sensor as instructed in
Make sure sensor is in process with
sufficient sample stream (refer to
Chapter 2 for installation details).
Section 4.2 and replace sensor if defec-
tive.
Section 4.2 and replace sensor if defec-
tive.
Section 4.1 or Section 4.3.2. Replace
sensor if cracked.
Section 4.1 or Section 4.3.2. Replace
sensor if cracked.
Replace sensor.
Section 4.1 or Section 4.3.2. Replace
sensor if cracked.
Troubleshooting
Instruction Manual 31
Troubleshooting
Rosemount 389/389VP pH/ORP Sensor Accessories InformationTable 5-2:
Part number Description
11275-01 Handrail mounting assembly
12707-00 Jet spray cleaner
2002011 CPVC in-line tee, 1.5 in. size, 1.0 in. threaded process connection ends
915240-03 PVC in-line tee, 2.0 in. size, 3/4 in. threaded process connection ends
915240-04 PVC in-line tee, 2.0 in. size, 1.0 in. threaded process connection ends
915240-05 PVC in-line tee, 2.0 in. size, 1.5 in. threaded process connection ends
23242-02 Insertion mounting adapter, 1.5 in. MNPT process connection, 1 in. x 3/4 in. FPT sensor
adapter/union thread size
33081-00 PEEK adapter insert, 1 x 3/4 in., for 23242-02
23646-01 11-conductor extension cable, shielded and prepped (for use with remote junction box)
9200273 11-conductor extension cable, shielded and unprepped (for use with remote junction box)
24091-00 Low flow cell, 1 in. sensor threaded connectio, 1/4 in. process connection
23555-00 Weatherproof junction box with preamplifier
2002565 Mounting bracket kit
9210012 pH 4.01 buffer solution, 16 oz
9210013 pH 6.86 buffer solution, 16 oz
9210014 pH 9.18 buffer solution, 16 oz
24281-00 15 ft VP8 cable
24281-01 25 ft VP8 cable
24281-02 2.5 ft VP8 cable
24281-03 50 ft VP8 cable
24281-04 100 ft VP8 cable
24281-05 4 ft VP8 cable
24281-06 10 ft VP8 cable
24281-07 20 ft VP8 cable
24281-08 30 ft VP8 cable
32 389/389VP
6 Return of Material
For all repair or return of material requests, please contact the factory.
Return of Material
Instruction Manual 33
Return of Material
34 389/389VP
EC Declaration of Conformity
7 EC Declaration of Conformity
Note: Please see website for most recent Declaration.
Instruction Manual 35
EC Declaration of Conformity
36 389/389VP
Intrinsically Safe Sensor Installation Drawing - FM
8 Intrinsically Safe Sensor Installation
Drawing - FM
Instruction Manual 37
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