Emerson ROSEMOUNT 242 User manual

Model 242
Flow-Through Toroidal Conductivity Sensor
Instruction Manual
PN 51-242/rev E
March 2012

CAUTION
SENSOR/PROCESS
APPLICATION COMPATIBILITY
The wetted sensor materials may not be compatible
with process composition and operating conditions.
Replacement of original components with those con-
structed from alternative materials might change the
pressure, temperature, and/or performance specifi-
cations from those of the original sensor configura-
tion. Application compatibility is entirely the respon-
sibility of the user.
DANGER
HAZARDOUS AREA INSTALLATION
Installations near flammable liquids or in hazardous
area locations must be carefully evaluated by qual-
ified on site safety personnel. This sensor is not
Intrinsically Safe or Explosion Proof.
To secure and maintain an intrinsically safe installa-
tion, the certified safety barrier, transmitter, and
sensor combination must be used. The installation
system must comply with the governing approval
agency (FM, CSA, BASEEFA/CENELEC, or ATEX)
hazardous area classification requirements.
Consult your analyzer/transmitter instruction manu-
al for details.
Replacement of original components with those con-
structed from alternative materials will void any
CSA, FM, and BASEEFA/CENELEC agency
approvals that were applicable to the original device.
Proper installation, operation and servicing of this
sensor in a Hazardous Area Installation 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 instru-
ments 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 maintain-
ing Rosemount Analytical products. Failure to follow the proper/ instruc-
tions 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, tele-
phone [phone] 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, opera-
tion, 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, for example, ANSI B16.5. Connect all products to the
proper electrical and pressure sources.
• To ensure proper performance, qualified personnel should install,
operate, and maintain the product.
• When replacement parts are required, ensure that qualified people
use replacement parts specified by Rosemount Analytical.
Replacement of original components with those constructed from
alternative materials will void any CSA, FM, and BASEEFA/CEN-
ELEC agency approvals that were applicable to the original device.
Furthermore, replacement of original components with those con-
structed from alternative materials might change the pressure, tem-
perature, and/or performance specifications from those of the original
configuration. Ensure replacement parts are compatible with process
requirements. Unauthorized parts and procedures can affect the
product’s performance, place the safe operation of your process at
risk, and 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: [phone]
Fax: [phone]
http://www.rosemountanalytical.com
© Rosemount Analytical Inc. 2012

i
MODEL 242 TABLE OF CONTENTS
MODEL 242
TOROIDAL CONDUCTIVITY SENSOR
TABLE OF CONTENTS
Section Title Page
1.0 MODEL 242 SENSOR............................................................................................. 1
1.1 Features and Applications........................................................................................ 1
1.2 Specifications ........................................................................................................... 2
1.3 Ordering Information ................................................................................................ 5
1.4 Installation................................................................................................................ 7
1.5 Calibration................................................................................................................ 10
1.6 Maintenance ............................................................................................................ 13
2.0 Troubleshooting..................................................................................................... 14
3.0 Replacement Parts................................................................................................. 16
3.1 General .................................................................................................................... 16
3.2 Remove the Sensor From the Process.................................................................... 16
3.3 Disassemble the Sensor .......................................................................................... 16
3.4 Re-assemble the Sensor ......................................................................................... 19
3.5 Re-install the Sensor into the Process..................................................................... 19
4.0 Return of Materials ................................................................................................ 20
LIST OF TABLES
Table No. Title Page
1-1 Nominal Cell Constants for 242 Sensors................................................................. 10
2-1 Resistance vs. Temperature for RTD (Resistance Temperature Detector) ............. 14
2-2 Sensor Resistance Check........................................................................................ 14
3-1 Replacement Parts and Accessories ....................................................................... 17
3-2 Sensor Bolt Removal & Installation Guide............................................................... 18

LIST OF FIGURES
Figure No. Title Page
1-1 Pressure-Temperature Specs for 1”, 1.5”, & 2” Sensors: Models 242-02/03/04 .... 3
1-2 Pressure-Temperature Specs for 3” & 4” Sensors: Models 242-06/08 ................... 3
1-3 Pressure-Temperature Specs for 1” & 2” Sensors: Alumina Liner .......................... 4
1-4 Pressure-Temperature Specs for 3” & 4” Sensors: Alumina Liner .......................... 4
1-5 Dimensional Drawing ............................................................................................... 7
1-6 Installation and Torque Guidelines........................................................................... 8
1-7 Sensor to Junction Box Wiring ................................................................................ 9
1-8 Sensor/Junction Box/RTD Assembly ....................................................................... 9
1-9 Extension Cable ...................................................................................................... 10
1-10 Extension Cable to Instrument Model 54eC Wiring................................................ 11
1-11 Extension Cable to Instrument Model 1055 Wiring ................................................. 11
1-12 Extension Cable to Instrument Models 3081T & 4081T Wiring............................... 12
1-13 Extension Cable to Instrument Model 81T Wiring ................................................... 12
1-14 Extension Cable to Instrument Model Xmt Pipe/Wall Mount Enclosure.................. 12
1-15 Extension Cable to Instrument Model Xmt Panel Mount Enclosure........................ 13
2-1 Sensor Circuit for Troubleshooting .......................................................................... 15
3-1 Model 242 Sensor - Exploded View ........................................................................ 18
3-2 Flange Assembly...................................................................................................... 19
MODEL 242 TABLE OF CONTENTS
MODEL 242
TOROIDAL CONDUCTIVITY SENSOR
ii
About This Document
This manual contains instructions for installation and operation of the Model 242 Flow-Through
Toroidal Conductivity Sensor. The following list provides notes concerning all revisions of this doc-
ument.
Rev. Level Date Notes
A 11/02 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 8/03 Corrected wiring references in text and drawings. Added information regarding
ATEX approvals with Model 5081T.
C 5/04 Added information regarding the alumina liner, and updated wiring diagrams.
D
E 03/12 Update addresses pages 22 and 24

1
MODEL 242 SECTION 1.0
242 SENSOR
SECTION 1.0
242 SENSOR
1.1 FEATURES AND APPLICATIONS
Rosemount Analytical Toroidal Conductivity Sensors
are ideal for use in processes where contacting sen-
sors -- those with electrodes exposed to the measured
solution -- would corrode or become fouled.
The 242 Flow Through Toroidal conductivity sensor
consists of two toroids surrounding a pipe through
which the process liquid flows. One toroid acts as a
transmitter and the other as a receiver. Energizing the
transmitter toroid induces an electric current in the
process solution which induces an electric current in
the receiver toroid. The strength of the induced current
is directly proportional to the conductivity of the solu-
tion.
The 242 sensor is available in over two hundred fifty
configurations to meet the needs of many applications
and installations. Line sizes of 1, 1.5, 2, 3, and 4 inch-
es (25, 40, 50, 80, and 100 mm) are available with
both ANSI and DIN compatible flanges. A variety of
liner materials and O-rings are available to ensure
compatibility with most process liquids.
The 242 sensor is easy to install. It fits in the process
piping between mounting flanges. Special grounding
rings are not needed because the sensor has con-
tact rings built into it. Recessed bolts hold the sensor
together to ensure all internal parts stay in perfect
alignment. A junction box and a Pt 100 RTD are
included. The RTD slips easily into one of the sensor
contact rings. There is no need to install a separate
thermowell, and temperature measurements are
made at the same point as the conductivity measure-
ments.
The sensor is not sensitive to flow rate or direction.
It does not obstruct the process flow. The sensor is
rugged and constructed from chemically resistant
materials. All these features make the sensor ideal
for applications in mining and metals processing,
pulp and paper processing, and the chemical pro-
cessing industry.
The 242 Flow Through Conductivity Sensor is com-
patible with instrument instumentsL 54eC, 1055,
3081T, 4081T, 5081-T, and Xmt-T.
• FLOW THROUGH DESIGN is ideal for use with viscous,
abrasive, or fibrous process liquids.
• OVER 250 CONFIGURATIONS to meet customers' needs.
• REPLACEABLE LINER in glass-filled PEEK, TEFLON, or
ALUMINA reduces long-term operating costs.
• DIN and ANSI FLANGES compatible with all piping instal-
lations.
• LINE SIZES of 1 through 4 inches (DN 25, 40, 50, 80 and
100).
• IN-LINE CALIBRATION saves money by reducing labor
and down-time.
• TEMPERATURE SENSOR and JUNCTION-BOX included.

2
MODEL 242 SECTION 1.0
MODEL 242 SENSOR
1.2 SPECIFICATIONS
The Model 242 Flow Through Sensor comprises a toroid
housing constructed from 316 stainless steel and polyeth-
yleneterephthalate, process connection flanges of 316
stainless steel, two metal contact rings (available in choice
of three materials), an insulating liner (choice of three
materials), O-rings (choice of three materials), a Pt 100
RTD, and a sensor-mounted junction box. Only the liner,
contact rings, and O-rings are wetted by the process. The
Pt 100 RTD is designed for insertion into one pre-drilled
contact ring. The NEMA 7D junction box is constructed of
heavy duty epoxy-painted cast aluminum. The conductivity
range is user-selectable with the tapped toroid windings.
In-line calibration can be performed with resistors connect-
ed to an integral wire around the toroids that is terminated
in the junction box.
Liners are available in Teflon, glass-filled Polyetheretherketone (PEEK), and alumina. These materials provide
excellent chemical resistance. PEEK is recommended for high pressure or high temperature applications.
Teflon is recommended when the process solution contains hydrofluoric acid or other strong oxidizing agents.
Alumina is recommended if the process solution is abrasive, such as in alumina/caustic ratio applications.
Teflon is a registered trademark of E.I. du Pont de Nemours & Co.
Viton is a registered trademark of Du Pont Dow Elastomers.
Carpenter 20Cb-3 is a registered trademark of Carpenter Technologies.
Hastelloy is a registered trademark of Haynes International.
Chemraz is a registered trademark of Greene, Tweed, & Co.
Installation Type Flow Through
Conductivity Range 100 μS/cm to 2 S/cm
Process Connections 150# ANSI, 300# ANSI, PN16 DIN 2501 compatible flanges
Maximum Temperature Depends on configuration. For plastic-lined sensors, see charts on facing page.
For alumina-lined sensors, see charts on page 4.
Maximum Pressure Depends on configuration. For plastic-lined sensors, see charts on facing page.
For alumina-lined sensors, see charts on page 4.
Wetted Materials: Liner Teflon®(PTFE), glass-filled PEEK, or alumina
Contact Rings 316 SST, Carpenter 20Cb-3®SST, or Hastelloy®C-276
O-rings EPDM, Viton®(FKM), or Chemraz®(FFKM)
Shipping Weight 1” to 2”: 22 lbs. (10kg)
3” to 4”: 86 lbs. (39 kg)
Pt 100 RTD
Flange
Contact Ring
Liner
O-ring (not visible)

3
MODEL 242 SECTION 1.0
MODEL 242 SENSOR
FIGURE 1-1. Pressure - Temperature Specifications for 1”, 1.5”, and 2” (25, 40, and 50 mm) Sensors:
Models 242-02, 242-03, and 242-04
FIGURE 1-2. Pressure - Temperature Specifications for 3” and 4” (80 and 100 mm) Sensors:
Models 242-06 and 242-08
steam
steam

MODEL 242 SECTION 1.0
MODEL 242 SENSOR
4
FIGURE 1-3. Pressure - Temperature Specifications for 1” and 2” Sensors: Alumina Liner
FIGURE 1-4. Pressure - Temperature Specifications for 3” and 4” Sensors: Alumina Liner

MODEL 242 SECTION 1.0
MODEL 242 SENSOR
5
1.3 ORDERING INFORMATION
The 242 Flow-Through Sensor is configurable to meet the needs of many applications and installations (both
ANSI and DIN). After specifying line size and flange type, the customer selects the wetted materials most compat-
ible with the process stream. A NEMA 7D junction box and Pt 100 RTD are also included. Compatible instruments
include Rosemount Analytical Models 54eC, 1055, 3081T, 4081T, 5081-T, and Xmt-T.
The extension cable required for wiring from the junction box to the instrument must be ordered separately. The
customer supplies the gaskets, mating flanges, and flange bolts.
CODE LINE SIZE (Required Selection)
02 1” DN 25
03 1-1/2” DN 40
04 2” DN 50
06 3” DN 80 (no ATEX approval with 5081T)
08 4” DN 100 (no ATEX approval with 5081T)
CODE PROCESS CONNECTION (Required Selection)
10 150# ANSI Flange (Line sizes 1", 1-1/2", 2”, 3”, 4”)
11 300# ANSI Flange (Line sizes 1", 1-1/2", 2”, 3”, 4”)
14 PN 16 Metric Flange (Line sizes DN 25, 40, 50, 80, 100)
242 FLOW THROUGH TOROIDAL CONDUCTIVITY SENSOR
CODE CONTACT RING MATERIAL (Required Selection)
SS 316 Stainless Steel
H4 Hastelloy C-276 (Line Sizes 1", 1-1/2", 2”, 25mm, 40mm, 50mm)
H8 Hastelloy C-276 (Line Sizes 3", 4", 80mm, 100mm)
C4 Carpenter 20-Cb3 (Line Sizes 1", 1-1/2", 2”, 25mm, 40mm, 50mm)
C8 Carpenter 20-Cb3 (Line Sizes 3", 4", 80mm, 100mm)
CODE PROCESS O-RING MATERIAL (Required Selection)
EP Ethylene Propylene Rubber
VT Fluorocarbon Rubber (Viton
®)
F4 High Temp. Perfluoroelastomer (Chemraz
®)
(Line Sizes 1", 1-1/2", 2”, 25mm, 40mm, 50mm)
F8 High Temp. Perfluoroelastomer (Chemraz
®) (Line Sizes 3", 4",
80mm, 100mm
)
CODE LINER MATERIAL (Required Selection)
TE PTFE (Teflon
®
)
G4 PEEK, 30% Glass-Filled (Line Sizes 1", 1-1/2", 2”, 25mm, 40mm, 50mm)
G8 PEEK, 30% Glass-Filled (Line Sizes 3", 4", 80mm, 100mm)
A4 Alumina (Line sizes 1”, 2”, 25 mm, 50 mm); available only with option F4
A8 Alumina (Line sizes 3”, 4”, 80 mm, 100 mm); available only with option F8
242 -0611SSG8VT EXAMPLE

6
MODEL 242 SECTION 1.0
MODEL 242 SENSOR
PART NUMBER DESCRIPTION
23909-00 Extension cable, Pre-prepped, for connection to Instrument Models 54eC, 1055, 3081T,
4081T, 5081-T, and Xmt-T (Specify length)
KIT PN DESCRIPTION FOR SENSOR MODELS
24005-00 Kit, Liner, 1” DN 25, Teflon PTFE 242-02[ ]TE[ ]
24005-01 Kit, Liner, 1” DN 25, glass-filled PEEK 242-02[ ]G4[ ]
24005-02 Kit, Liner, 1” DN 25, Alumina 242-02[ ]A4[ ]
24006-00 Kit, Liner, 1-1/2” DN 40, Teflon PTFE 242-03[ ]TE[ ]
24006-01 Kit, Liner, 1-1/2” DN 40, glass-filled PEEK 242-03[ ]G4[ ]
24007-00 Kit, Liner, 2” DN 50, Teflon PTFE 242-04[ ]TE[ ]
24007-01 Kit, Liner, 2” DN 50, glass-filled PEEK 242-04[ ]G4[ ]
24007-02 Kit, Liner, 2” DN 50, Alumina 242-04[ ]A4[ ]
24008-00 Kit, Liner, 3” DN 80, Teflon PTFE 242-06[ ]TE[ ]
24008-01 Kit, Liner, 3” DN 80, glass-filled PEEK 242-06[ ]G8[ ]
24008-02 Kit, Liner, 3” DN 80, Alumina 242-06[ ]A8[ ]
24009-00 Kit, Liner, 4” DN 100, Teflon PTFE 242-08[ ]TE[ ]
24009-01 Kit, Liner, 4” DN 100, glass-filled PEEK 242-08[ ]G8[ ]
24009-02 Kit, Liner, 4” DN 100, Alumina 242-08[ ]A8[ ]
KIT PN DESCRIPTION FOR SENSOR MODELS
24010-00 Kit, O-Ring, 1” DN 25, EPDM 242-02[ ]EP[ ]
24010-01 Kit, O-Ring, 1” DN 25, Viton 242-02[ ]VT[ ]
24010-02 Kit, O-Ring, 1” DN 25, Chemraz 242-02[ ]F4[ ]
24010-03 Kit, O-Ring, 1” DN 25, Chemraz for use with Alumina liner 242-02[ ]A4-F4
24011-00 Kit, O-Ring, 1-1/2” DN 40, EPDM 242-03[ ]EP[ ]
24011-01 Kit, O-Ring, 1-1/2” DN 40, Viton 242-03[ ]VT[ ]
24011-02 Kit, O-Ring, 1-1/2” DN 40, Chemraz 242-03[ ]F4[ ]
24012-00 Kit, O-Ring, 2” DN 50, EPDM 242-04[ ]EP[ ]
24012-01 Kit, O-Ring, 2” DN 50, Viton 242-04[ ]VT[ ]
24012-02 Kit, O-Ring, 2” DN 50, Chemraz 242-04[ ]F4[ ]
24012-03 Kit, O-Ring, 2” DN 50, Chemraz for use with Alumina liner 242-04[ ]A4-F4
24013-00 Kit, O-Ring, 3” DN 80, EPDM 242-06[ ]EP[ ]
24013-01 Kit, O-Ring, 3” DN 80, Viton 242-06[ ]VT[ ]
24013-02 Kit, O-Ring, 3” DN 80, Chemraz 242-06[ ]F8[ ]
24013-03 Kit, O-Ring, 3” DN 80, Chemraz for use with Alumina liner 242-06[ ]A8-F8
24014-00 Kit, O-Ring, 4” DN 100, EPDM 242-08[ ]EP[ ]
24014-01 Kit, O-Ring, 4” DN 100, Viton 242-08[ ]VT[ ]
24014-02 Kit, O-Ring, 4” DN 100, Chemraz 242-08[ ]F8[ ]
24014-03 Kit, O-Ring, 4” DN 100, Chemraz for use with Alumina liner 242-08[ ]A8-F8
ACCESSORIES

7
1.4 INSTALLATION
In the instructions below, the Junction Box is installed
after the sensor is bolted into the process line. If appropri-
ate for the site and final mounting configuration, the
Junction Box can be installed prior to bolting the sensor
into the process line.
CAUTION
The liner of the Model 242 sensor can be damaged if mis-
handled. Do NOT place any object through the liner for
the purpose of lifting the Model 242 sensor.
CAUTION
Support structures should be installed as appropriate on
or around process pipes and sensor location to sufficient-
ly support the weight of the sensor during installation and
minimize strain on adjacent process pipes during the
operational life of the sensor.
MODEL 242 SECTION 1.0
MODEL 242 SENSOR
Installation of the Model 242 Flow Through Sensor is simi-
lar to installation of a section of pipe. Consequently, be
prepared to use tools, supplies, equipment, and tech-
niques similar to those used to install process pipes. Use
common piping practices to minimize torque and bending
loads on process connections. Observe all applicable
safety standards. Dimensional information is shown in
Figure 1-5 below. Refer to Figures 1-6 to 1-8 for assembly
and installation diagrams.
NOTES
1. Allow at least four pipe diameters of straight pipe run
on either side of the sensor.
2. Install the sensor so that it is filled with process liquid
at all times when measurements are being made.
Avoid downward flow as such a configuration might
leave the sensor partially empty.
3. Use a sling and hoist to lift and position the sensor.
FIGURE 1-5. DIMENSIONAL DRAWING
INCH
MILLIMETER

8
MODEL 242 SECTION 1.0
MODEL 242 SENSOR
INSTALLING THE SENSOR IN THE PROCESS LINE
1. Install process flanges in accordance with applicable instructions, standards, and local regulations.
2. Position the sensor between the process mating flanges with flange gaskets inserted between each set of
flanges. Ensure that the locations of the junction box connection and the RTD hole in the contact ring are in
the correct position for easy wiring and use.
3. Align the bolt holes in the sensor and process flanges.
4. Lubricate the bolt threads. Using a torque wrench, bolt the sensor into place. Tighten the bolts in 1/3 incre-
ments of the final desired torque. Follow the bolt-tightening sequence and torque suggestions provided in
Figure 1-6.
5. Re-torque the bolts 12 to 24 hours after installation. Make a final check of torque values by moving consecu-
tively from bolt to bolt.
FIGURE 1-6. Installation and Torque Guidelines
Torque values in the table above are from Garlock Sealing Technologies. Other values might apply
when using different bolt and gasket materials.
Gylon® is a registered Trademark of Garlock Sealing Technologies.

9
ATTACHING THE JUNCTION BOX
1. Pull the sensor wires up into the junction box.
2. Screw the junction box onto the threaded male connection on
the sensor. Use of pipe sealing tape or other compound is at the
discretion of the customer.
3. Connect the sensor wires to the junction box terminal as indicat-
ed in Figure 1-7.
INSTALLING THE Pt100 RTD
1. Use of the included Pt100 RTD is recommended. Use of a cus-
tomer-supplied Pt100 or Pt1000 TC mounted in a separate ther-
mowell is also acceptable. The accuracy specifications provided
by Rosemount Analytical apply only to situations wherein the
Pt100 RTD supplied with the sensor is used.
2. Refer to Figure 1-8. Screw the threaded nipple onto the conduit
connector of the junction box. Screw the tee onto the nipple, and
screw the RTD cable connector onto the tee.
3. Attach the bracket to the shaft of the RTD using the #10 washer
and small screw enclosed in the RTD kit. The purpose of the
bracket is to retain the RTD in the contact ring after installation.
4. Slide the Pt100 RTD into the pre-drilled hole in the contact ring.
Rotate the bracket to a position beneath the junction box, and
tighten the set screw.
5. Thread the RTD wires through cable connector, tee, nipple, and into junction box. Wire the RTD to the junction box terminals as
indicated in Figure 1-7. Install the white jumper wire between terminals 1 and 2.
MODEL 242 SECTION 1.0
MODEL 242 SENSOR
FIGURE 1-7. Sensor to Junction Box Wiring
*For optimal performance below 10,000 µS/cm, connect
green wire from extension cable to terminal indicated by *
FIGURE 1-8. Sensor/J-box/RTD Assembly
Items 1-9 are included with the Model 242
sensor. Items 3-9, the white jumper wire,
and Teflon tape are included in the TC kit.
Items 10 and 11 are sold separately as
accessories.

10
MODEL 242 SECTION 1.0
MODEL 242 SENSOR
EXTENSION CABLE HOOK UP
1. Do not run sensor cable in conduit or open trays
with A.C. power wiring. Do not route sensor cable
near heavy electrical equipment.
2. For best sensor/instrument loop performance, use
factory-terminated extension cable (PN 23909-00).
(Using a different cable can introduce noise into
the signal and/or reduce loop accuracy.)
3. One end of extension cable (PN 23909-00) has 8
wires, and the other end has 11 wires. Refer to
Figure 1-9. The end with 8 wires goes into the junc-
tion box. The end with 11 wires goes to the instru-
ment. The extension cable enters the junction box
through the open side of the female threaded tee.
Use of conduit, the optional cable connector (PN
9310137), or other strain relief device to protect the
cable is at the discretion of the customer and
should comply with applicable agency guidelines.
NOTE
If starting with unprepped cable (PN 9200276), remove
only as much insulation as is necessary. The instru-
ment end needs 11 leads: four leads from the green-
white-black-drain bundle, three from each of the two
coaxial cable bundles (the inner conductor, the insulat-
ing braid, and the drain wire), and one from the outer-
most overall braided-copper shield. For the junction
box end, only 8 leads are used: the white coaxial con-
ductor, its braided shield, the green coaxial conductor,
its braided shield, its drain wire, and the green, white,
and black conductors from the green-white-black-drain
bundle. The remaining shields and drain wires are not
used on the junction box end and should be removed -
- they should NOT be connected.
4. Connect the 8 wires of the extension cable to the
terminal block inside the sensor junction box as
indicated in Figure 1-7. Note: If all process meas-
urements will be less than 10,000 µS/cm, connect
the green wire from the black-green-clear wire bun-
dle of the extension cable to the terminal receiving
the orange sensor wire. See Figure 1-7.
5. Connect the 11 wires of the instrument-end of the
extension cable according to the applicable dia-
gram from Figures 1-10 through 1-15.
1.5 CALIBRATION
After sensor and transmitter/analyzer wiring is com-
pleted, calibrate the sensor.
NOTE
Most analyzers require the input of the approximate
sensor cell constant before the analyzer calculates the
true cell constant. The nominal cell constant of the
Model 242 sensor depends on the size of the sensor
and the terminal to which the receive wire of the inter-
connecting cable is attached. Refer to Table 1-1 for
the appropriate nominal cell constant value.
FIGURE 1-9. Extension Cable
TABLE 1-1: Nominal Cell Constants for 242 Sensors
Sensor Size Cell Constant (/cm)*
Black Orange
1”, DN 25 20 2.0
1.5”, DN 40 9.0 0.90
2”, DN 50 5.0 0.50
3”, DN 80 4.0 0.40
4”, DN 100 2.3 0.23
* The table gives the cell constant when the green receive
wire (from black-green-clear bundle) of the interconnect-
ing cable is attached to either the black wire terminal or
the orange wire terminal in the sensor junction box. See
Figures 1-7 and 2-1.

11
MODEL 242 SECTION 1.0
MODEL 242 SENSOR
FIGURE 1-10. Extension Cable to
Model 54eC Wiring
FIGURE1-11. Extension Cable to Model 1055 Wiring
NOTE: If wiring to a single
channel 1055-21 or to a dual
channel 1055-21-xx or 1055-
xx-31, the toroidal sensor is
wired only to Terminal Blocks
3 and 4. If wiring 2 sensors to
a dual toroidal 1055-21-31, use
TB 3, 4, and 5 as shown.

FIGURE 1-12. Extension Cable to Models 3081T,
4081T, and 5081T Wiring
FIGURE 1-13. Extension Cable to Model 81T
Wiring
FIGURE 1-14. Extension Cable to Model Xmt Pipe/Wall Mount Enclosure
*
* Applies only to 3081T
and 4081T.
12
MODEL 242 SECTION 1.0
MODEL 242 SENSOR
SELECT
HI OR
LO

13
FIGURE 1-15. Extension Cable to Model Xmt Panel Mount Enclosure
MODEL 242 SECTION 1.0
MODEL 242 SENSOR
A. To perform liquid calibration prior to installing the sensor in the process line, first seal one end of the sensor,
and then proceed with the following steps.
1. Stand the sensor on the sealed end.
2. Fill the sensor completely with a standard conductivity solution.
3. Insert the Pt100 RTD into the contact ring.
4. Adjust the analyzer reading so that it matches the conductivity of the standard solution at the solution tem-
perature. Refer to the analyzer/ transmitter instruction manual for complete calibration procedures.
B. Use of the Integral Calibration Loop Wire: This internal wire can be used to facilitate future in-process loop cal-
ibration and to perform a quick verification that the loop is functioning properly. Performing this additional (but
optional) step is highly recommended.
1. The sensor must be empty of all fluids, reasonably clean, and preferably completely dry.
2. Attach a variable resistance decade box to the sensor yellow “Cal Loop” wires (in the junction box).
3. Adjust the applied resistance until the instrument reads the same conductivity value that it did during the
liquid calibration process. Record the conductivity, applied resistance value, and temperature for future ref-
erence.
4. To recalibrate the loop at a later date, optimal results will be achieved if the sensor is returned to a condi-
tion approximating its condition during the initial performance of steps C.1 to C.3 above. If this is not pos-
sible, the sensor must at least be empty of process fluids. Reapply the same resistance to the Cal Loop
and adjust the instrument reading.
1.6 MAINTENANCE
The only routine maintenance required during the operational life of the sensor is to ensure that there are no
deposits plugging the sensor or coating the inside of the contact rings. Some customers find it advantageous to
periodically replace process gaskets and/or re-tighten the flange bolts to ensure adequate process seals. Refer to
Figure 1-6 for flange bolting sequence and torque recommendations.

14
MODEL 242 SECTION 2.0
TROUBLESHOOTING
SECTION 2.0
TROUBLESHOOTING
2.1 TROUBLESHOOTING. The simplest method of trou-
bleshooting is to run a resistance test on the inductive
sensing device. It is also recommended to check the
resistance of the RTD and resistance between various
pairs of the sensor wires.
To perform a quick resistance check of the sensor, recall
the data obtained during Part C of the Calibration
Process (Refer to Section 1.5) With the sensor empty of
process fluids (preferably also clean and dry), reapply
the resistance to the sensor yellow Cal Loop wires in the
junction box. The reading should be with ±20% of the
original value.
To check the RTD, measure the resistance across the
RTD wires. See Figure 1-4. The resistance value should
be close to the value shown in Table 2-1.
Refer to Figure 2-1 for a circuit diagram of the sensor to
use as an aid when performing the resistance checks.
Use Table 2-2 to determine the resistance values that
should be found across various pairs of sensor wires.
TABLE 2-1 Resistance Values for Pt100 RTD
Temperature Resistance
(°C/°F) (Ohms)
18 / 64.4 106.9
19 / 66.2 107.3
20 / 68.0 107.7
21 / 69.8 108.1
22 / 71.6 108.4
23 / 73.4 108.9
24 / 75.2 109.2
25 / 77.0 109.6
26 / 78.8 110.0
27 / 80.6 110.4
C = Celsius / F = Fahrenheit
TABLE 2-2 Sensor Wire Resistance Values
Connection Resistance
(Wire colors are for sensor wires unless indicated)
GREEN to ORANGE < 1 Ohm
GREEN to BLACK 1 to 5 Ohms
GREEN to GROUND screw in J-box (GRAY wire) > 20 MegOhms
GREEN to WHITE > 20 MegOhms
GREEN to YELLOW > 20 MegOhms
WHITE to GRAY < 1 Ohm
WHITE to GROUND screw in J-box (GRAY wire) > 20 MegOhms
WHITE to YELLOW > 20 MegOhms
WHITE to RED > 20 MegOhms
YELLOW to YELLOW < 1 Ohm
YELLOW to GROUND screw in J-box (GRAY wire) > 20 MegOhms

15
MODEL 242 SECTION 2.0
MODEL 242 SENSOR
FIGURE 2-1. Sensor Circuit for Troubleshooting
*The green wire from the extension cable’s black-green-clear bundle might be connected opposite the
sensor’s orange wire, as indicated by *to utilize the sensor’s alternative cell constant.

16
3.1 GENERAL
When replacement parts are required, ensure that
qualified people install the parts specified by
Rosemount. Replacement of original components with
those constructed from alternative materials might
change the temperature, pressure, and/or performance
specifications from those of the original configuration
and will void any CSA, FM, and BASEEFA/CENELEC
agency approvals that were applicable to the original
device. Table 3-1 lists the replacement parts kits for the
Model 242 Sensor. An instruction manual is included
with each kit.
3.2 REMOVE THE SENSOR
The RTD can be removed either before or after the
sensor is removed from the process. The junction box
should be left attached to the toroid subassembly. After
ensuring that it is safe to remove the sensor from the
process line, loosen the flange bolts in 1/3 increments
in the same order in which they were tightened as
shown in Figure1-4. Remove the bolts and sensor.
3.3 DISASSEMBLE THE SENSOR
Using the tool indicated in Table 3-2, remove the
Sensor Bolts (Item 2). Note that these bolts were
installed using a thread-locking adhesive. Any use of
heat to loosen the adhesive should not exceed the tem-
perature ratings of the sensor. Figure 3-1 is an explod-
ed view of the all the parts of the Model 242 sensor.
MODEL 242 SECTION 3.0
REPLACEMENT PARTS
SECTION 3.0
REPLACEMENT PARTS
CAUTION
Before removing the sensor from the process piping,
ensure that the process has been shut down and liq-
uid drained from the sensor line. For personal safety,
NOTE REGARDING O-RINGS
There are two pairs of O-rings inside the sensor:
process O-rings (item 6) and secondary or backup
O-rings (item 7). Refer to Figure 3-1 to identify these
items. The two pairs of O-rings are not interchange-
able.
Older O-ring replacement kits contained only the pair
of process O-rings. New O-ring replacement kits con-
tain both pairs of O-rings. To distinguish the process
O-ring from the backup O-ring:
For sensors with plastic liners:
1. The process O-ring has a much smaller cross sec-
tional area than the secondary O-ring. The cross-
section diameter of the process O-ring is 0.07 in.
The cross-section diameter of the secondary O-ring
is 0.139 in.
2. The diameter of the process O-ring is less than
the secondary O-ring. The size difference is
immediately obvious when the two O-rings are
allowed to dangle from a pencil.
For sensors with alumina liners:
1. The process and secondary O-rings have the
same cross sectional area. (0.139 in).
2. The diameter of the process O-ring is less than
the secondary O-ring. The size difference is
immediately obvious when the two O-rings are
allowed to dangle from a pencil.