Rosemount 248H Operating Manual
Reference Manual
00809-0100-4825, Rev CB
Rosemount® 248 Temperature Transmitter
March 2014
Reference Manual
NOTICE
00809-0100-4825, Rev CB
Rosemount 248 Temperature
Transmitter
Rosemount 248 Hardware Revision
Headmount
Railmount
®
HART
Device Revision
Field Communicator Field Device Revision
Read this manual before working with the product. For personal and system safety, and for
optimum product performance, make sure to thoroughly understand the contents before
installing, using, or maintaining this product.
The United States has two toll-free assistance numbers and one international number.
Customer Central
1 800 999 9307 (7:00 a.m. to 7:00 P.M. CST)
National Response Center
1 800 654 7768 (24 hours a day)
Equipment service needs
International
1 952 906 8888
4
1
5.1
Dev v1, DD v1
The products described in this document are NOT designed for nuclear-qualified
applications.
Using non-nuclear qualified products in applications that require nuclear-qualified
hardware or products may cause inaccurate readings.
For information on Rosemount nuclear-qualified products, contact an Emerson Process
Management Sales Representative.
v
Reference Manual
00809-0100-4825, Rev CB
Content
1Section 1: Introduction
Table of Contents
March 2014
1.1 Safety messages. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1.1 Warnings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
1.2 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.2.1 Manual . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.2.2 Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.3 Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
1.3.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
1.3.2 Commissioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
1.3.3 Mechanical . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
1.3.4 Electrical . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
1.3.5 Environmental . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
1.4 Return of materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.5 Product recycling/disposal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
2Section 2: Installation
2.1 Safety messages. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.1.1 Warnings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7
2.2 Mounting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
2.3 Installation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10
2.3.1 Typical European and Asia Pacific installation . . . . . . . . . . . . . . . . . . . . . . . .10
2.3.2 Typical North and South American installation . . . . . . . . . . . . . . . . . . . . . . .11
2.4 Multichannel installations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14
2.5 Set the switches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14
2.5.1 Failure mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14
2.6 Wiring. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15
2.6.1 Sensor connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16
2.7 Power supply. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18
2.7.1 Surges/transients . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19
2.7.2 Ground the transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19
Table of Contents
3Section 3: Configuration
3.1 Safety messages. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
3.1.1 Warnings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
3.2 Commissioning. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24
3.2.1 Setting the loop to manual . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24
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March 2014
Reference Manual
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3.3 AMS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24
3.3.1 Apply AMS changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25
3.4 Field communicator. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25
3.4.1 HART traditional menu tree . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26
3.4.2 HART device dashboard menu tree. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27
3.4.3 Fast Key sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28
3.4.4 Review configuration data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30
3.4.5 Check output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30
3.4.6 Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30
3.4.7 Information variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33
3.4.8 Diagnostics and service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34
3.5 Multidrop communication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .39
3.6 Rosemount 248 Configuration Interface specifications . . . . . . . . . . . . . . . . . . . . .40
3.6.1 Configuration software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40
3.6.2 Configuration hardware . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40
3.6.3 Rosemount 248 PC Programmer Kit installation . . . . . . . . . . . . . . . . . . . . .41
4Section 4: Operation and maintenance
4.1 Safety messages. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43
4.1.1 Warnings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43
4.2 Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .44
4.2.1 Trim the transmitter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .44
4.3 Hardware . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .46
4.3.1 Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .46
4.4 Diagnostic messages. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .47
4.4.1 Hardware . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .47
4.4.2 Field communicator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .49
AAppendix A: Specifications and reference data
A.1 Transmitter specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .51
A.1.1 Functional specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .51
A.1.2 Physical specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .53
A.1.3 Performance specifications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .54
A.2 Sensor specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .57
viii
A.2.1 Thermocouples – IEC 584 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .57
A.2.2 Thermocouples – ASTM E- 230 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .58
A.2.3 RTDs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .58
A.2.4 Thermowells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .59
Table of Contents
Reference Manual
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BAppendix B: Product Certifications
Table of Contents
March 2014
A.3 Dimensional drawings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .60
A.4 Ordering information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .62
B.1 Approved Manufacturing Locations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .65
B.2 European Directive Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .65
B.3 Ordinary Location Certification from FM Approvals . . . . . . . . . . . . . . . . . . . . . . . .65
B.3.1 North America . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .65
B.3.2 Europe. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .66
B.3.3 International . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .68
B.3.4 China . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .69
B.3.5 Combinations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .71
B.3.6 Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .72
B.4 Installation drawings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .72
Table of Contents
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Section 1 Introduction
Safety messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 1
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 2
Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 3
Return of materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 5
Product recycling/disposal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 5
1.1 Safety messages
Instructions and procedures in this section may require special precautions to ensure the safety
of the personnel performing the operations. Information that potentially raises safety issues is
indicated by a warning symbol ( ). Please refer to the following safety messages before
performing an operation preceded by this symbol.
Section 1: Introduction
March 2014
1.1.1 Warnings
Failure to follow these installation guidelines could result in death or
serious injury.
Make sure only qualified personnel perform the installation.
Explosions could result in death or serious injury.
Do not remove the connection head cover in explosive atmospheres when the
circuit is live.
Before connecting a Field Communicator in an explosive atmosphere, make sure the
instruments in the loop are installed in accordance with intrinsically safe or
non-intrinsic field wiring practices.
Verify that the operating atmosphere of the transmitter is consistent with the
appropriate hazardous locations certifications.
All connection head covers must be fully engaged to meet
explosion-proof requirements.
Process leaks could result in death or serious injury.
Do not remove the thermowell while in operation.
Install and tighten thermowells and sensors before applying pressure
Electrical shock could cause death or serious injury.
Use extreme caution when making contact with the leads and terminals.
Introduction
1
Section 1: Introduction
March 2014
1.2 Overview
1.2.1 Manual
This manual is designed to assist in the installation, operation, and maintenance of the
Rosemount 248 Temperature Transmitter.
Section 1: Introduction
Transmitter and Manual Overview
Things to considerations
How to return the transmitter
Section 2: Installation
How to mount the transmitter
How to Install the transmitter
How to set the switches to ensure proper use
How to wire and power up the transmitter
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Section 3: Configuration
Commissioning to transmitter
How to use the Field Communicator to configure the transmitter
Section 4: Operation and maintenance
Calibration the transmitter
Explanation of hardware maintenance and diagnostic messages
Appendix A: Specifications and reference data
Transmitter and Sensor Specifications
Dimensional drawings
Ordering Information
Appendix B: Product Certifications
Product Certifications/Hazardous Locations Certifications
Installation Drawings
1.2.2 Transmitter
Features of the Rosemount 248 include:
Acceptance of inputs from a wide variety of RTD and thermocouple sensors
Configuration using HART protocol
Electronics encapsulated in epoxy and enclosed in a plastic housing, making the
transmitter extremely durable and ensuring long-term reliability
A compact size and three housing options that allow mounting flexibility in the field
2
Introduction
Reference Manual
00809-0100-4825, Rev CB
Refer to the following literature for sensors, thermowells, and extensions that form a complete
point solution with the Rosemount 248:
Temperature Sensors and Assemblies Product Data Sheet, Volume 1 (Document No.
00813-0100-2654)
Temperature Sensors and Assemblies Product Data Sheet, Volume 2 (Document No.
00813-0200-2654)
Temperature sensors and Assemblies Product Data Sheet, Volume 3 (Document No.
00813-0301-2654)
1.3 Considerations
1.3.1 General
Electrical temperature sensors, such as RTDs and thermocouples, produce low-level signals
proportional to the sensed temperature. The Rosemount 248 converts the low-level sensor
signal to a standard 4–20 mA dc signal that is relatively insensitive to lead length and electrical
noise. This current signal is transmitted to the control room through two wires.
Section 1: Introduction
March 2014
1.3.2 Commissioning
The transmitter may be commissioned before or after installation. It can be useful to
commission it on the bench, before installation, to ensure proper operation and to become
familiar with its functionality. The instruments in the loop should be installed according to the
intrinsically safe or non-incendive field wiring practices before connecting a Field
Communicator in an explosive atmosphere. For more information, see “Commissioning” on
page 24.
1.3.3 Mechanical
Location
When choosing an installation location, take into account access to the transmitter.
Special mounting
Special hardware is available for mounting a Rosemount 248 head mount transmitter to a DIN
rail.
1.3.4 Electrical
Proper electrical installation is necessary to prevent errors from sensor lead resistance and
electrical noise. For best results, shielded cable should be used in electrically noisy
environments. A resistance between 250 and 1100 ohms must be present in the loop for
communication with a Field Communicator.
Introduction
Make wiring connections through the cable entry in the side of the connection head being sure
to provide adequate clearance for cover removal.
3
Section 1: Introduction
60
50
40
30
20
10
0
75 10 125 150 175 200 225
Temperature rise above ambient (°C)
Extension length (mm)
8
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5
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March 2014
1.3.5 Environmental
The transmitter electronics module is permanently sealed within the housing, to resist moisture
and corrosive damage. Verify that the operating atmosphere of the transmitter is consistent
with the appropriate hazardous locations certifications.
Temperature effects
The transmitter operates within specifications for ambient temperatures between –40 and 185
°F (–40 and 85 °C). Process heat from the process is transferred from the thermowell to the
transmitter housing so if the expected process temperature is near or above specification limits,
consider using an additional thermowell lagging, and extension nipple, or a remote mounting
configuration to isolate the transmitter from the process.
Figure 1-1 provides an example of the relationship between transmitter housing temperature
rise and extension length.
Figure 1-1. Rosemount 248 Transmitter Connection Head Temperature rise vs. Extension
Length
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4
Example
The transmitter specification limit is 85 °C. If the ambient temperature is 55 °C and the process
temperature to be measured is 800 °C, the maximum permissible connection head temperature
rise is the transmitter specification limit minus the ambient temperature (moves 85 to 55 °C), or
30 °C.
In this case, an extension of 100 mm meets this requirement, but 125 mm provides a margin of
8 °C, reducing any temperature effects in the transmitter.
Introduction
Reference Manual
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1.4 Return of materials
To expedite the return process in North America, call the Emerson Process Management
National Response Center toll-free at 800-654-7768. This center is available 24 hours a day and
will assist you with any needed information or materials.
The center will ask for the following information:
Product model
Serial numbers
The last process material to which the product was exposed
The center will provide
A Return Material Authorization (RMA) number
Instructions and procedures that are necessary to return goods that were exposed to
hazardous substances
Note
If a hazardous substance is identified, a Material Safety Data Sheet (MSDS), required by law to be
available to people exposed to specific hazardous substances, must be included with the
returned materials.
Section 1: Introduction
March 2014
Outside North America, contact a local Emerson Process Management representative.
1.5 Product recycling/disposal
Recycling of equipment and packaging should be taken into consideration and disposed of in
accordance with local and national legislation/regulations.
Introduction
5
Reference Manual
00809-0100-4825, Rev CB
Section 2 Installation
Safety messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 7
Mounting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 9
Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 10
Set the switches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 14
Wiring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 15
Power supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 18
2.1 Safety messages
Instructions and procedures in this section may require special precautions to ensure the safety
of the personnel performing the operations. Information that potentially raises safety issues is
indicated by a warning symbol ( ). Please refer to the following safety messages before
performing an operation preceded by this symbol.
Section 2: Installation
March 2014
2.1.1 Warnings
Failure to follow these installation guidelines could result in death or
serious injury.
Make sure only qualified personnel perform the installation.
Explosions could result in death or serious injury.
Do not remove the connection head cover in explosive atmospheres when the
circuit is live.
Before connecting a communicator in an explosive atmosphere, make sure the
instruments in the loop are installed in accordance with intrinsically safe or
non-incendive field wiring practices.
Verify that the operating atmosphere of the transmitter is consistent with the
appropriate hazardous locations certifications.
All connection head covers must be fully engaged to meet
explosion-proof requirements.
Process leaks could result in death or serious injury.
Do not remove the thermowell while in operation.
Install and tighten thermowells and sensors before applying pressure
Electrical shock could cause death or serious injury.
Use extreme caution when making contact with the leads and terminals.
Installation
7
Section 2: Installation
START
HERE
Bench
calibration
BASIC SETUP
Set Sensor type
Set Number of wires
Set Units
Set Range values
Set Damping
VERIFY
Simulate Sensor input
Within
Specifications
Refer to Section 4: Operation and
maintenance
FIELD INSTALL
Mount transmitter
Wire transmitter
Power transmitter
FINISHED
March 2014
Figure 2-1. Installation Flowchart
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A
C
00809-0100-4825, Rev CB
2.2 Mounting
Mount the transmitter at a high point in the conduit run to prevent moisture from draining into
the transmitter housing.
The Rosemount 248R installs directly to a wall or to a DIN rail.
The Rosemount 248H installs:
In a connection head or universal head mounted directly on a sensor assembly
Apart from a sensor assembly using a universal head
To a DIN rail using an optional mounting clip
Mounting a Rosemount 248H to a DIN rail
To attach a head mount transmitter to a DIN rail, assemble the appropriate rail mounting kit
(part number 00248-1601-0001) to the transmitter as shown in Figure 2-2.
Figure 2-2. Assembling Rail Clip Hardware to a Rosemount 248
Section 2: Installation
March 2014
Installation
A. Mounting hardware
B. Transmitter
C. Rail clip
9
Section 2: Installation
A
D
B
C
E
F
March 2014
2.3 Installation
The Rosemount 248 can be ordered assembled to a sensor and thermowell or as a stand-alone
unit. If ordered without the sensor assembly, use the following guidelines when installing the
transmitter with an integral sensor assembly.
2.3.1 Typical European and Asia Pacific installation
Head mount transmitter with DIN plate style sensor
1. Attach the thermowell to the pipe or process container wall then install and tighten the
thermowell before applying process pressure.
2. Assemble the transmitter to the sensor. Push the transmitter mounting screws through
the sensor mounting plate and insert the snap rings (optional) into the transmitter
mounting screw groove.
3. Wire the sensor to the transmitter (see “Sensor wiring Diagrams” on page 16).
Reference Manual
00809-0100-4825, Rev CB
4. Insert the transmitter-sensor assembly into the connection head. Thread the
transmitter mounting screw into the connection head mounting holes and assemble
the extension to the connection head then insert the assembly into the thermowell.
5. Slip the shielded cable though the cable gland
6. Attach a cable gland into the shielded cable.
7. Insert the shielded cable leads into the connection head through the cable entry then
connect and tighten the cable gland.
8. Connect the shielded power cable leads to the transmitter power terminals making
sure to avoid contact with sensor leads and sensor connections.
9. Install and tighten the connection head cover making sure the enclosure covers are fully
engaged to meet explosion-proof requirements.
A. Rosemount 248 transmitter D. Transmitter mounting screws
B. Connection head E. Integral mount sensor with flying leads
C. Thermowell F. E xt ensi on
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Installation
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B
C
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00809-0100-4825, Rev CB
2.3.2 Typical North and South American installation
Head mount transmitter with threaded sensor
1. Attach the thermowell to the pipe or process container wall then install and tighten
thermowells before applying process pressure.
2. Attach necessary extension nipples and adapters to the thermowell making sure to seal
the nipple and adapter threads with silicone tape.
3. Twist the sensor into the thermowell and install drain seals, if required, for severe
environments or to satisfy code requirements.
4. Pull the sensor wiring leads through the universal head and transmitter. Mount the
transmitter in the universal head by threading the transmitter mounting screws into
the universal head mounting holes.
5. Mount the transmitter-sensor assembly into the thermowell sealing the adapter
threads with silicone tape.
Section 2: Installation
March 2014
6. Install conduit for field wiring to the conduit entry of the universal head making sure to
seal the conduit threads with silicone tape.
7. Pull the field wiring leads through the conduit into the universal head. Attach the sensor
and power leads to the transmitter. Avoid contact with other terminals.
8. Install and tighten the universal head cover. Enclosure covers must be fully engaged to
meet explosion-proof requirements.
A. Threaded thermowell D. Universal head
B. Threaded style sensor E. Conduit entry
C. Standard extension
Installation
11
Section 2: Installation
C
D
E
F
A
B
March 2014
Rail mount transmitter with integral mount sensor
The least complicated assembly uses:
an integral mount sensor with terminal block
an integral DIN style connection head
a standard extension
a threaded thermowell
Refer to the Metric Product Data Sheet (Document No. 00813-0101-2654) for complete sensor
and mounting accessory information.
To complete the assembly:
1. Attach the transmitter to a suitable rail or panel.
2. Attach the thermowell to the pipe or process container wall. Install and tighten the
3. Attach the sensor to the connection head and mount the entire assembly to the
Reference Manual
00809-0100-4825, Rev CB
thermowell before applying pressure.
thermowell.
4. Attach sufficient lengths of sensor lead wire to the sensor terminal block.
5. Attach and tighten the connection head cover. Enclosure covers must be fully engaged
to meet explosion-proof requirements.
6. Run sensor lead wires from the sensor assembly to the transmitter.
7. Attach the sensor and power leads to the transmitter. Avoid contact with leads and
terminals.
Figure 2-3. Typical Rail Mount Transmitter Mounting Configuration using integral
Mount Sensor and Assembly
12
A. Rail mount transmitter D. Connection head
B. Sensor leads with cable gland E. Standard extension
C. Integral mount sensor with terminal block F. T hr eade d t herm owel l
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C
E
D
B
00809-0100-4825, Rev CB
Rail mount transmitter with threaded sensor
The least complicated assembly uses:
a threaded sensor with flying heads
a threaded sensor connection head
a union and nipple extension assembly
a threaded thermowell
Refer to Volume 1 of the Rosemount Sensors Product Data Sheet (Document No.
00813-0100-2654) for complete sensor and mounting accessory information.
To complete the assembly:
1. Attach the transmitter to a suitable rail or panel.
2. Attach the thermowell to the pipe or process container wall. Install and tighten the
3. Attach necessary extension nipples and adapters. Seal the nipple and adapter threads
Section 2: Installation
March 2014
thermowell before applying pressure.
with silicone tape.
4. Twist the sensor into the thermowell. Install drain seals if required for severe
environments or to satisfy code requirements.
5. Screw the connection head to the sensor.
6. Attach the sensor lead wires to the connection head terminals.
7. Attach additional sensor lead wires from the connection head to the transmitter.
8. Attach and tighten the connection head cover. Enclosure covers must be fully engaged
to meet explosion-proof requirements.
9. Attach the sensor and power leads to the transmitter. Avoid contact with leads and
terminals.
Figure 2-4. Typical Rail Mount Transmitter Mounting Configuration using
Threaded Style Sensor and Assembly
Installation
A. Rail mount transmitter D. Standard extension
B. Threaded sensor connection head E. Threaded thermowell
C. Threaded style sensor
13
Section 2: Installation
A
B
C
C
C
D
E
H
G
F
Between 250 and 1100 if no load resistor.
March 2014
2.4 Multichannel installations
Several transmitters can be connected to a single master power supply, as shown in Figure 2-5.
In this case, the system may be grounded only at the negative power supply terminal. In
multichannel installations, where several transmitters are dependent on one power supply and
the loss of all transmitters would cause operational problems, consider an uninterrupted power
supply or a back-up battery. The diodes shown in Figure 2-5 prevent unwanted charging or
discharging of the back-up battery.
Figure 2-5. Multichannel Installations
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00809-0100-4825, Rev CB
A. Transmitter no. 1 E. Readout or Controller no. 2
B. Transmitter no. 2 F. Backup battery
C. R
Lead
D. Readout or Controller no. 1 H. To additional transmitters
2.5 Set the switches
2.5.1 Failure mode
Each transmitter continuously monitors its performance during normal operation with an
automatic diagnostic routine of continuous timed series of checks. If an input sensor failure or a
transmitter electronics failure is detected, the transmitter outputs the low or high alarm,
depending on the failure mode configuration.
For sensor temperature outside of range limits:
Standard Saturation Levels:
3.90 mA on the low end
20.5 mA on the high end
NAMUR-Compliant Saturation Levels:
G. dc Power supply
3.80 mA on the low end
20.5 mA on the high end
These values are also custom configurable by the factory or using the Field Communicator or
AMS. See “Alarm and saturation” on page 36 for instructions on how to change the alarm and
saturation levels with the Field Communicator.
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Note
Microprocessor failures cause high alarm regardless of alarm direction (high or low) choice.
The values the transmitter drives its output in failure mode depend on if it is configured to
standard, NAMUR-compliant, or custom operation. See “Software detected failure mode” on
page 52 for standard and NAMUR-compliant operation parameters.
2.6 Wiring
All power to the transmitter is supplied over the signal wiring. Ordinary copper wire of sufficient
size should be used to ensure the voltage across the transmitter power terminals does not drop
below 12.0 Vdc. Verify that the operating atmosphere of the transmitter is consistent with the
appropriate hazardous locations certifications. Always use extreme caution when making
contact with the leads and terminals.
If the sensor is installed in a high-voltage environment and a fault condition or installation error
occurs, the sensor leads and transmitter terminals could carry lethal voltages. Use extreme
caution when making contact with the leads and terminals.
Section 2: Installation
March 2014
Note
Do not apply high voltage (e.g., ac line voltage) to the transmitter terminals since high voltage
can damage the unit. (Sensor and transmitter power terminals are rated up to 42.4 Vdc.) Use
extreme caution when making contact with the leads and terminals.
For multichannel installations, see page 14. The transmitters accept inputs from a variety of RTD
and thermocouple types. Refer to Figure 2-7 on page 16 when making sensor connections.
Use the following steps to wire the transmitter:
1. Remove the terminal block cover (if applicable).
2. Connect the positive power lead to the “+” terminal. Connect the negative power lead
to the “–” terminal (see Figure 2-6). Use extreme caution when making contact with
the leads and terminals.
3. Tighten the terminal screws.
4. Reattach and tighten the cover (if applicable). All connection head covers must be fully
engaged to meet explosion-proof requirements
5. Apply power (see “Power supply”).
.
Installation
15
Section 2: Installation
44.0 (1.7)
33
12.9 (0.51)
24.5 (0.97)
C
B
A
1234234 12 34 1234
1
2-wire
RTD and
3-wire*
RTD
and
T/C
and mV
4-wire RTD
and
March 2014
Figure 2-6. Rosemount 248 wiring
Reference Manual
00809-0100-4825, Rev CB
Power, communication and
sensors terminals
Note: Signal loop may be grounded at any single point or left ungrounded.
Note: A Field Communicator may be connected at any termination point in the signal loop. The signal loop must have between 250 and
1100 ohms load for communications.
Connecting a communicator to a transmitter loop
A. Field communicator
B. Power supply
C. 250 R
1100
L
2.6.1 Sensor connections
The Rosemount 248 is compatible with a number of RTD and thermocouple sensor types.
Figure 2-7 shows the correct input connections to the sensor terminals on the transmitter. To
ensure proper sensor connection, anchor the sensor lead wires to the appropriate compression
terminals and tighten the screws. Use extreme caution when making contact with the leads and
terminals.
Figure 2-7. Sensor wiring Diagrams
Rosemount 248 Sensor connections diagram
* Emerson Process Management provides 4-wire sensors for all single element RTDs. Use these RTDs in 3-wire
configurations by leaving the unneeded leads disconnected and insulated with electrical tape.
Thermocouple or millivolt inputs
The thermocouple can be connected directly to the transmitter. Use appropriate thermocouple
extension wire if mounting the transmitter remotely from the sensor. Make millivolt input
connections with copper wire, and use shielding for long runs of wire.
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Installation
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Basic Error
Imbalance of Lead Wires
PtRo
------------------------------------------------------------ ----- -
=
Error due to amb. temp. variation
Cu
T
amb
Imbalance of Lead Wires
Pt
Ro
---------------------------------------------------------------- ---------------------------------------------------------
=
00809-0100-4825, Rev CB
RTD or ohm inputs
The transmitters accepts a variety of RTD configurations, including 2-wire, 3-wire and 4-wire
designs. If the transmitter is mounted remotely from a 3-wire or 4-wire RTD, it will operate
within specifications, without recalibration, for lead wire resistances up to 60 ohms per lead (or
the equivalent to 6,000 feet of 20 AWG wire). In this case, the leads between the RTD and
transmitter should be shielded. If using only two leads, the RTD leads are in series with the
sensor element, so significant errors can occur when the lead lengths exceed three feet of
20 AWG wire (approximately 0.05 °C/ft). For longer runs, attach a third or fourth lead, as
described above.
Sensor lead wire resistance effect– RTD input
When using a 4-wire RTD, the effect of lead resistance is eliminated and does not impact
accuracy. However, a 3-wire sensor will not fully cancel lead resistance error it cannot
compensate for imbalances in resistance between the lead wires. Using the same type of wire
on all three lead wires makes a 3-wire RTD installation the most accurate. A 2-wire sensor
produces the largest error since it directly adds the lead wire resistance to the sensor resistance.
For 2- and 3-wire RTDs, an additional lead wire resistance error is induced with ambient
temperature variations. The table and the examples shown on Tab l e 2 - 1help quantify these
errors.
Section 2: Installation
March 2014
Table 2-1. Examples of Approximate Basic Error
Sensor input Approximate basic error
4-wire RTD None (independent of lead wire resistance)
3-wire RTD ± 1.0 in reading per ohm of unbalanced lead wire resistance
2-wire RTD 1.0 in reading per ohm of lead wire resistance
(Unbalanced lead wire resistance = maximum imbalance
between any two leads.)
Examples of approximate lead wire resistance effect calculations
Given:
Total cable length: 150 m
Imbalance of the lead wires at 20 °C: 0.5
Resistance/length (18 AWG Cu): 0.025 /m °C
Temperature coefficient of Cu (Cu): 0.039 / °C
Temperature coefficient of Pt(Pt): 0.00385 / °C
Change in Ambient Temperature (T
RTD Resistance at 0 °C (Ro): 100 (for Pt 100 RTD)
Pt100 4-wire RTD: No lead wire resistance effect.
Pt100 3-wire RTD:
): 25 °C
amb
Installation
17
Section 2: Installation
Basic error
0.5
0.00385 / C100
----------------------------------------------------------- ---------------------- -
1.3 C==
Error due to amb. temp. var. of 25 °C
0.0039 / C25 C 0.5
0.00385 / C100
----------------------------------------------------------- --------------------------------------------
0.13·C==
Basic Error
Lead Wire Resistance
PtRo
----------------------------------------------------------
=
Error due to amb. temp. variation
Cu
T
amb
Lead Wire Resistance
Pt
Ro
--------------------------------------------------------------- --------------------------------------------------
=
Basic error
7.5
0.00385 / C100
------------------------------------------------------------ --------------------- -
19.5 C==
Error due to amb. temp. var. of 25 °C
0.0039 / C25 C 7.5
0.00385 / C100
--------------------------------------------------------------- ----------------------------------------
1.9 C==
4–20 mA dc
1322
1100
1000
750
500
250
0
10
12.0
20 30 40 42.4
Load (Ohms)
Supply voltage (V dc)
Operating
region
Maximum load = 40.8 x (Supply voltage – 12.0)
March 2014
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00809-0100-4825, Rev CB
Lead wire imbalance seen by the transmitter = 0.5
Pt100 2-wire RTD:
Lead wire resistance seen by the transmitter = 150 m × 2 wires × 0.025
/m = 7.5
2.7 Power supply
To communicate with a transmitter, an 18.1 Vdc minimum power supply is required. The power
supplied to the transmitter should not drop below the transmitter lift-off voltage (see
Figure 2-8). If the power drops below the lift-off voltage while the transmitter is being
configured, the transmitter may interpret the configuration information incorrectly.
The dc power supply should provide power with less than 2 percent ripple. The total resistance
load is the sum of the resistance of the signal leads and the load resistance of any controller,
indicator, or related pieces of equipment in the loop. Note that the resistance of intrinsic safety
barriers, if used, must be included.
Figure 2-8. Load Limits
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2.7.1 Surges/transients
The transmitter will withstand electrical transients of the energy level encountered in static
discharges or induced switching transients. However, high-energy transients, such as those
induced in wiring from nearby lightning strikes, welding, heavy electrical equipment, or
switching gears, can damage both the transmitter and the sensor. To protect against
high-energy transients, install the transmitter in a suitable connection head with the
Rosemount 470 Transient Protector. Refer to the Rosemount 470 Transient Protector Product
Data Sheet (Document No. 00813-0100-4191) for more information.
2.7.2 Ground the transmitter
The transmitter operates with the current signal loop either floating or grounded. However,
extra noise in floating systems may affect many types of readout devices. If the signal appears
noisy or erratic, grounding the current signal loop at a single point may solve the problem. The
best place to ground the loop is at the negative terminal of the power supply. Do not ground the
current signal loop at more than one point.
The transmitter is electrically isolated to 500 Vac rms (707 Vdc), so the input circuit may also be
grounded at any single point. When using a grounded thermocouple, the grounded junction
serves as this point.
Section 2: Installation
March 2014
Note
Do not ground the signal wire at both ends.
Ungrounded thermocouple, mV, and RTD/ohm inputs
Each process installation has different requirements for grounding. Use the grounding options
recommended by the facility for the specific sensor type, or begin with grounding Option 1 (the
most common).
Option 1:
1. Connect sensor wiring shield to the transmitter housing (only if the housing is
grounded).
2. Make sure that the sensor shield is electrically isolated from surrounding fixtures that
may be grounded.
3. Ground signal wiring shield at the power supply end.
Installation
A. Transmitter C. 4-20 mA loop
B. Sensor wires D. Shield ground point
19
Section 2: Installation
B
C
D
Connect shields together, electrically isolated from the transmitter
A
CB
D D
A
March 2014
Option 2 (for ungrounded housing):
1. Connect signal wiring shield to the sensor wiring shield.
2. Make sure that the two shields are tied together and electrically isolated from the
3. Ground shield at the power supply end only.
4. Ensure that the sensor shield is electrically isolated from the surrounding grounded
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00809-0100-4825, Rev CB
transmitter housing.
fixtures.
A. Transmitter C. 4-20 mA loop
B. Sensor wires D. Shield ground point
Option 3:
1. Ground sensor wiring shield at the sensor, if possible.
2. Make sure that the sensor wiring and signal wiring shields are electrically isolated from
the transmitter housing.
3. Do not connect the signal wiring shield to the sensor wiring shield.
4. Ground signal wiring shield at the power supply end.
A. Transmitter C. 4-20 mA loop
B. Sensor wires D. Shield ground point
20
Installation
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