rtd and thermocouple assemblies reference manual...the compensating cable for a thermocouple must be...

Reference Manual 00809-0301-2654, Rev BASeptember 2009

RTD and Thermocouple Assemblies Reference Manual

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Reference Manual 00809-0301-2654, Rev BASeptember 2009 RTD and Thermocouple

Mounting and Installation Advice for Resistance Thermometers and Thermocouple Assemblies

NOTICE

Read this manual before working with the product. For personal and system safety, and for optimum product performance, make sure you thoroughly understand the contents before installing, using, or maintaining this product.

For further details please contact your local Rosemount representative.

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 your local Emerson Process Management Sales Representative.

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Table of Contents

SECTION 1Introduction

How to Use this Manual. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1Safety Messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1

SECTION 2Temperature Measurement with Resistance Thermometers

Description and Measuring Principle . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1Methods of Connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3Areas of Application. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4

SECTION 3Temperature Measurement with Thermocouples

Description and Measurement Principle . . . . . . . . . . . . . . . . . . . . . . . 3-1Installation of Protective Tubes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3Leads and Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3Areas of Application. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3

SECTION 4Assembly of Housing

Rules and Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1Stress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1Torque . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1Housing Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1Ceramic Housing Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2Connection of Transmitters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2

APPENDIX ALimit Tolerances of the Basic Values

APPENDIX BLimit tolerances for Thermocouples

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Reference Manual00809-0301-2654, Rev BA

September 2009RTD and Thermocouple

TOC-2


Section 1 Introduction

How to Use this Manual . . . . . . . . . . . . . . . . . . . . . . . . . . . page 1-1Safety Messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 1-1

HOW TO USE THIS MANUAL

This manual provides installation, configuration, troubleshooting, and other procedures for the use of the Rosemount1075 Series. Specifications and other important information are also included.

Section 2: Temperature Measurement with Resistance Thermometers

Contains information on description and measuring principle, structure, methods of connection and areas of application.

Section 3: Temperature Measurement with Thermocouples

Contains information on description and measurement principle, installation of protective tubes, leads and connections, and areas of application.

Section 4: Assembly of Housing

Contains information on rules and regulations for the Rosemount 1075 Series.

Appendix A: Limit Tolerances of Basic Values

Provides a chart with the limit tolerances of the basic values according to DIN IEC 751 and DIN 43760.

Appendix B: Limit Tolerances for Thermocouples

Provides a chart for limit tolerances for thermocouples according to DIN IEC 584-2.

SAFETY MESSAGES Procedures and instructions in this manual may require special precautions to ensure the safety of the personnel performing the operations. Refer to the safety messages, listed at the beginning of each section, before performing any operations.

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1-2


Section 2 Temperature Measurement with Resistance Thermometers
Description and Measuring Principle . . . . . . . . . . . . . . . . page 2-1Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 2-1Methods of Connection . . . . . . . . . . . . . . . . . . . . . . . . . . . page 2-3Areas of Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 2-4
DESCRIPTION AND MEASURING PRINCIPLE

Temperature measurement with resistance thermometers is based on the property possessed by all conductors and semiconductors, namely that their resistance varies as a function of temperature. This property is more or less pronounced, depending on the particular material. The relative change in the resistance as a function of temperature (dR/dt) is known as the temperature coefficient, the value of which is usually not constant over the range of temperature of interest, but is itself a function of temperature. The result is that the mathematical relationship between resistance and temperature takes the form of a high-order polynomial.

Figure 2-1 shows the change in resistance as a function of temperature for a Pt 100 resistance thermometer.

Figure 2-1. Pt 100 characteristic curve

STRUCTURE The resistance temperature detector is made up of a platinum coil wound on a suitable support. The wire coil is either fused into glass or embedded in ceramic. To meet today’s requirements for more compact dimensions and higher resistance values, extremely thin platinum layers are applied to a ceramic substrate instead of wires (see Figure 2-2).

0

100

-200

200

300

400

2000 400 600 800

R

t

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Figure 2-2. Glass wire-wound, ceramic wire-wound and thin-film resistance thermometers

To protect them against mechanical damage (pressure of flowing liquid) these measuring elements are usually installed into suitable protective tubes (measuring inserts). This also ensures easy replacement without the need to replace the complete fitting. As resistance thermometers are contact-making temperature sensors (i.e. the sensor has to reach the temperature of the medium in which measurement is to be performed) the housing has to be adapted to the application (see Figure 2-3).

Figure 2-3. Resistance thermometer modules

Connection wires

Measuring coil

Ceramic substrate

Strain relief

Connection wires

Glass

Measuring coil

Ceramic tube

Aluminum oxide powder

Glass

Connection wires

Glass carrier

Measuring coil

Glass sheath

Connection wires

Glass carrier

Measuring coil

Glass sheath

Measuring resistance

Measuring insert

Housing

2-2


METHODS OF CONNECTION

When using resistance thermometers for temperature measurement, the fact that the measurement result is influenced by the resistance of the selected lead wire must be taken into account.

Three circuit types are commonly used: 2-wire, 3-wire, and 4-wire circuits.

The most accurate measurements are obtained with the 4-wire circuit, as in this case the measurement is not affected by lead wire resistance or environment temperature of lead wires (see Figure 2-4).

The 3-wire circuit is normally used for eliminating the lead wire resistance (Wheatstone bridge).

In the case of the 2-wire circuit, the lead wire resistance is fully measured by the measuring bridge. By the use of modern control equipment the influence of the lead wire resistance at 2-wire circuit can be compensated by a line compensation resistor, which is independent of temperature.

Figure 2-4. Methods of connection

To measuring unit

To measuring unit

To measuring unit

2-3



AREAS OF APPLICATION

Resistance thermometers can be used over a temperature range of -220 C to +600 C.

Their advantages are:

• High temperature ranges

• Resistance to vibration

• High immunity to electrical interference

• Long-term stability

• Robust design

• High accuracy

Resistance thermometers are used in the following industries:

• Chemical industries

• Petrochemical industries

• Pharmaceutical industries

• Power generation

• Mechanical engineering

• Food & beverage

• Mining

2-4


Section 3 Temperature Measurement with Thermocouples
Description and Measurement Principle . . . . . . . . . . . . . page 3-1Installation of Protective Tubes . . . . . . . . . . . . . . . . . . . . . page 3-3Leads and Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . page 3-3Areas of Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 3-3
DESCRIPTION AND MEASUREMENT PRINCIPLE

A thermocouple consists of two electrical conductors of different materials connected to one another at one end (measuring junction). The two free ends build a compensation point resp reference junction. The thermocouple can be extended by using an extension or a compensating cable. The extension or compensating cables are connected to a measuring instrument, e.g. a galvanometer or electronic measuring unit (see Figure 3-1).

Figure 3-1.

The thermoelectric voltage appearing at the reference junction depends on the thermocouple wire material and on the temperature difference between the measuring junction and the reference junction. For temperature measurement, the temperature of the reference junction must be kept constant (e.g. 0 C) or must be well known, to make an appropriate correction in mV (see Figure 3-2).

Reference junction

Extension/compensating cable

Connection point

Measuring junction

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Figure 3-2.

Extension cables are manufactured of the same material as the corresponding thermocouple, e.g. Cu-CuNi, Fe-CuNi. Compensating cables are manufactured of special materials.

Up to 200 C compensating cables supply the same thermoelectric voltage as the thermocouples to which they are connected, The thermoelectric voltages of the thermocouples are laid down in so-called basic value series.

The compensating cable for a thermocouple must be make of a material to suit the particular type of thermocouple, so compensating leads are color-coded. For standardized compensating cable the regulations contained in DIN EN 60584 apply.

Maximum temperatures indicated by manufacturer have to be considered.

Most thermocouples are supplied ready for operation, that is in a protective mounting to prevent damage to the thermocouple by mechanical forces or chemical attack.

e.g. PtRh30%-PtRh6% Type BFe-CuNi Type JNiCr-NiAl Type JPtRh87/13%-Pt Type RPtRh90/10%-Pt Type Sand others in DIN IEC 584-1

and Fe-CuNi Type LCu0CuNi Type UThese thermocouples are not more available for use in new plants (thermoelectric voltage according to DIN 43710) Basic value tables are available on request only at manufacturer site.

Reference junction

Extension/compensating cable

Connection point

Measuring junction

Copper wire

3-2


INSTALLATION OF PROTECTIVE TUBES

The protective tubes of thermocouples must be adapted to the particular operating conditions. Precious metal thermocouples are always protected with a ceramic tube, even if the unit has a metallic protective mounting.

At high temperatures the protective tubes should be installed vertically, where possible, i.e. suspended, to avoid damage deflection to the protective tube and thermocouple through bending. If specific conditions on site make a horizontal installation unavoidable, long protective tubes have to be suitably supported.

LEADS AND CONNECTIONS

When laying and connecting extension resp. compensating cables, care must be taken to connect the positive pole of the thermocouple to the positive terminal of the indicating instrument. If extension cables or compensating cables are used, care must be taken not to interchange positive and negative conductors. To prevent errors, the positive and negative leads bear a corresponding marking.

All connections must be absolutely clean and firmly tightened. The corresponding positive and negative terminals should have the same temperature potential.

The compensating cables between the thermocouple and the indicating instrument should comply with the requirements for insulated leads in power systems (VDE 0250). In exceptional cases, the regulations for insulated leads in telecommunications systems (VDE 0810) may be applied.

AREAS OF APPLICATION

In the negative temperature range, thermocouples can be used down to -200 C. For temperatures above 1000 C, thermocouples made of platinum and a platinum/rhodium alloys are used.

Advantages of thermocouples are:

• Very high temperature ranges

• Fast response

• Compact design

• Extremely high resistance to vibration

• Long term stability

• Robust design

Thermocouples are used in the following, and other, industries:

• Chemical industries

• Pharmaceutical industries

• Power generation

• Mechanical engineering

• Food & beverage

• Mining

• Iron and steel

• Ceramics and glass

3-3



3-4


Section 4 Assembly of Housing

Rules and Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 4-1Stress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 4-1Torque . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 4-1Housing Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . page 4-1Ceramic Housing Installation . . . . . . . . . . . . . . . . . . . . . . page 4-2Connection of Transmitters . . . . . . . . . . . . . . . . . . . . . . . . page 4-2

RULES AND INSTRUCTIONS

For housing assembly, please use the following instructions.

VDE/VDI 3511Technical temperature measurement/instruction

VDE/VDI 3512 Set-up for temperature measurements

AD - instruction leaflets(1)

Working group pressure vessels

TRB - technical directions for tank construction(1)

Vd - TDV regulations(1)

Stress The stresses indicated in the drawing apply to the supplied housing. The load data, included in the standards for every type, are valid for housing according to DIN 43763 and DIN 43772.

Torque Starting torques for screw-in type threads

Applicable to screw-in type threads according to DIN 43763 and DIN 43772 as well as comparable housing according to customer’s specifications.

Above starting torques are to be used as well for coupling rings with similar threads.

Housing Assembly Assembly of housing with flange mounting

The seal is to be selected according to the requirements. During insertion of the seal, a good support is necessary. Fastening screws are to be tightened evenly and crosswise.

(1) To be considered in case of weld-in type tubes. Material, weld and pressure test according to operating conditions

G 3/8, G 1/2 50 NmG 3/4 100 Nm

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Ceramic Housing Installation

Installation of ceramic housing in plants at operating temperature

Temperature of the plant:

• 1600 C insertion speed: 1-2 cm/min.

• 1200 C insertion speed: 10-20 cm/min.

Connection of Transmitters

When connecting transmitter, the installation-, connection, and test instructions of the manufacturers are to be considered.

4-2


Appendix A Limit Tolerances of the Basic Values

Table A-1. Limit tolerances of the basic values according to DIN IEC 751 and DIN 43760

Basic values Limit tolerances

According to DIN IEC 751 Platinum RTD-elements

According to DIN 43760 Nickel RTD-elements

According to DIN IEC 751 Platinum RTD-elements

According to DIN 43760 Nickel RTD-elements

Class A Class B

C Ohm Ohm/K Ohm Ohm/K Ohm Corresp. C Ohm Corresp.C Ohm Corresp.C

-200 18.49 0.44 0.24 0.55 0.56 1.3

-100 60.25 0.41 0.14 0.35 0.32 0.8

-60 69.5 0.47 - 1.0 2.1

0 100.0 0.39 100.0 0.55 0.06 0.15 0.12 0.3 0.2 0.4

100 138.5 0.38 161.8 0.69 0.13 0.35 0.30 0.8 0.8 1.1

200 175.84 0.37 240.7 0.90 0.20 0.55 0.48 1.3 1.6 1.8

250 289.2 1.04 2.3 2.1

300 212.02 0.35 0.27 0.75 0.64 1.8

400 247.04 0.34 0.33 0.95 0.79 2.3

500 280.90 0.33 0.38 1.15 0.93 2.8

600 313.59 0.33 0.43 1.35 1.06 3.3

700 345.13 0.31 1.17 3.8

800 375.71 0.30 1.28 4.3

850 390.26 0.29 1.34 4.6

A-1



A-2


Appendix B Limit tolerances for Thermocouples

Table B-1. Limit tolerances for thermocouples according DIN IEC 584-2

Class 1 2 3(1)

(1) Thermocouples and thermocouple wires are usually supplied with limited tolerances according to the table above valid for temperature range above of -40 C. The thermocouple limit tolerances of same material at temperatures below -40 C may be exceeded as stated for tolerance class 3 according to DIN IEC 584-2. Thermocouples requested by purchaser with limit tolerances according to classes 1, 2, or 3 may be obtained by special material selection.

Limit tolerances(2)

(2) Limit tolerances for thermocouples are indicated in degrees centigrade or as percentage of the measured temperature in degrees centigrade. Whichever value is greater applies.

|t| = Temperature in degrees Centigrade

0.5 C or 0.004 x |t| 1 C or 0.0075 x |t| 1 C or 0.015 x |t|

(a) Limit tolerances apply to following temperature ranges

Type T -40 C up to 350 C -40 C up to 350 C -200 C up to 40 CLimit tolerances(2) 1.5 C or 0.004 x |t| 2.5 C or 0.0075 x |t| 2.5 C or 0.015 x |t|

() Limit tolerances apply to following temperature ranges

Type E -40 C up to 800 C -40 C up to 900 C -200 C up to 40 CType J -40 C up to 750 C -40 C up to 750 C --

Type K -40 C up to 1000 C -40 C up to 1200 C -200 C up to 40 CLimit tolerances(2) 1 C or [1+9t-1100) x 003] C 1.5 C or 0.0025 x |t| 4 C or 0.005 x |t|

() Limit tolerances apply to following temperature ranges

Type R and S 0 C up to 1600 C 0 C up to 1600 C --

Type B -- 600 C up to 1700 C 600 C up to 1700 C

B-1



B-2


Index

Numerics2-wire circuit . . . . . . . . . . . . . 2-33-wire circuit . . . . . . . . . . . . . 2-34-wire circuits . . . . . . . . . . . . 2-3

Aaccuracy . . . . . . . . . . . . . . . . 2-4AD - instruction leaflets . . . . . . 4-1

Bbasic values . . . . . . . . . . . . . A-1

Cceramic . . . . . . . . . . . . . . . . . 2-1ceramic substrate . . . . . . . . . 2-1ceramic tube . . . . . . . . . . . . . 3-3chemical attack . . . . . . . . . . . 3-2color-coded . . . . . . . . . . . . . . 3-2compact dimensions . . . . . . . . 2-1compensating cable . . . . . . . . 3-1Compensating cables . . . . . . . 3-2compensating leads . . . . . . . . 3-2conductors . . . . . . . . . . 2-1, 3-1Considerations . . . . . . . . . . . 2-2

Environmental . . . . . . . . . 2-4contact-making temperature sensors 2-2coupling rings . . . . . . . . . . . . 4-1

Ddesign . . . . . . . . . . . . . 2-4, 3-3DIN 43763 . . . . . . . . . . . . . . . 4-1DIN 43772 . . . . . . . . . . . . . . . 4-1DIN EN 60584 . . . . . . . . . . . . 3-2DIN IEC 584-2 . . . . . . . . . . . . B-1

Eelectrical interference . . . . . . . 2-4electronic measuring unit . . . . 3-1Environmental Considerations . 2-4Extension cables . . . . . . . . . . 3-2

FFastening screws . . . . . . . . . . 4-1function of temperature . . . . . . 2-1

Ggalvanometer . . . . . . . . . . . . 3-1glass . . . . . . . . . . . . . . . . . . 2-1

Hhermoelectric voltage . . . . . . . 3-2higher resistance values . . . . 2-1horizontal installation . . . . . . . 3-3housing assembly . . . . . . . . . 4-1

Iimmunity . . . . . . . . . . . . . . . 2-4independent of temperature . . 2-3installed vertically . . . . . . . . . 3-3

LLimit tolerances . . . . . . . A-1, B-1load data . . . . . . . . . . . . . . . 4-1

MMaximum temperature . . . . . . 3-2measurement result . . . . . . . . 2-3measuring bridge . . . . . . . . . 2-3measuring elements . . . . . . . 2-2measuring junction . . . . . . . . 3-1Measuring Principle . . . . . . . . 2-1mechanical damage . . . . . . . 2-2mechanical forces . . . . . . . . . 3-2metallic protective mounting . . 3-3mV . . . . . . . . . . . . . . . . . . . . 3-1

Nnegative conductor . . . . . . . . 3-3negative lead . . . . . . . . . . . . 3-3

Pplatinum . . . . . . . . . . . . . . . . 2-1platinum coil wound . . . . . . . . 2-1platinum thermocouples . . . . . 3-3platinum/rhodium alloys . . . . . 3-3positive lead . . . . . . . . . . . . . 3-3positive pole . . . . . . . . . . . . . 3-3positive terminal . . . . . . . . . . 3-3Precious metal thermocouples 3-3protective mounting . . . . . . . . 3-2protective tubes . . . . . . . .2-2, 3-3Pt 100 resistance thermometer 2-1

Rreference junction . . . . . . . . . .3-1replacement . . . . . . . . . . . . . .2-2Resistance . . . . . . . . . . . . . . .2-4resistance . . . . . . . . . . . . . . .2-3resistance temperature detector 2-1Resistance thermometer modules 2-2resistance thermometers . 2-1, 2-2response . . . . . . . . . . . . . . . .3-3

Sscrew-in type threads . . . . . . .4-1seal . . . . . . . . . . . . . . . . . . . .4-1semiconductors . . . . . . . . . . .2-1Specifications

HART and Foundation Fieldbus A-1

stability . . . . . . . . . . . . . 2-4, 3-3standards . . . . . . . . . . . . . . . .4-1support . . . . . . . . . . . . . . . . .3-3

TTemperature . . . . . . . . . . . . .2-1temperature coefficient . . . . . .2-1Temperature Measurement . . .3-1Temperature measurement . . .2-1temperature potential . . . . . . .3-3temperature range . . . . . . . . .2-4thermocouple . . . . . . . . . . . . .3-1thermocouple, . . . . . . . . . . . .3-2Thermocouples . . . . . . . . . . .3-1TRB - technical directions for tank construction . . . . . . . . . . . . . .4-1

VVd - TDV regulations . . . . . . . .4-1VDE/VDI 3511 . . . . . . . . . . . .4-1VDE/VDI 3512 . . . . . . . . . . . .4-1vibration . . . . . . . . . . . . . . . . .3-3voltage . . . . . . . . . . . . . . . . .3-1

Wwire material . . . . . . . . . . . . .3-1

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Reference Manual00809-0301-2654, Rev BASeptember 2009 RTD and Thermocouple

Index-2


September 2009

Emerson Process Management

00809-0301-2654 Rev BA, 09/09

Standard Terms and Conditions of Sale can be found at www.rosemount.com\terms_of_sale.The Emerson logo is a trademark and service mark of Emerson Electric Co.Rosemount, the Rosemount logotype, and Hot Backup are registered trademarks of Rosemount Inc.HART is a registered trademark of the HART Communication Foundation.FOUNDATION is a trademark of the Fieldbus Foundation.PlantWeb is a registered trademark of one of the Emerson Process Management companies.Teflon is a registered trademark of E.I. du Pont de Nemours & Co.All other marks are the property of their respective owners.

Rosemount Temperature GmbHFrankenstrasse 2163791 KarlsteinGermanyT 49 (6188) 992 0F 49 (6188) 992 112

Emerson Process Management Asia Pacific Private Limited1 Pandan CrescentSingapore 128461T (665) 777 8211F (665) 777 [email protected]

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rtd and thermocouple assemblies reference manual...the compensating cable for a thermocouple must be...

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