Because of the variety of uses for the products described in this publication,
those responsible for the application and use of this control equipment must
satisfy themselves that all necessary steps have been taken to assure that each
application and use meets all performance and safety requirements, including
any applicable laws, regulations, codes and standards.
The illustrations, charts, sample programs and layout examples shown in this
guide are intended solely for purposes of example. Since there are many
variables and requirements associated with any particular installation,
Allen-Bradley does not assume responsibility or liability (to include intellectual
property liability) for actual use based upon the examples shown in this
publication.
Allen-Bradley publication SGI-1.1, Safety Guidelines for the Application, Installation and Maintenance of Solid-State Control (available from your local
Allen-Bradley office), describes some important differences between solid-state
equipment and electromechanical devices that should be taken into
consideration when applying products such as those described in this
publication.
Reproduction of the contents of this copyrighted publication, in whole or part,
without written permission of Rockwell Automation, is prohibited.
Throughout this manual we use notes to make you aware of safety
considerations:
Configuration Worksheet for RTD/
Resistance Module
Appendix B
Glossary
Index
Publication 1746-UM003A-EN-P
Preface
Read this preface to familiarize yourself with the rest of the manual. This
preface covers the following topics:
• who should use this manual
• the purpose of this manual
• terms and abbreviations
• conventions used in this manual
• Allen-Bradley support
Who Should Use This
Manual
Purpose of This Manual
Use this manual if you are responsible for designing, installing, programming,
or troubleshooting control systems that use Allen-Bradley small logic
controllers.
You should have a basic understanding of SLC 500™ products. You should
understand programmable controllers and be able to interpret the ladder logic
instructions required to control your application. If you do not, contact your
local Allen-Bradley representative for information on available training courses
before using this product.
This manual is a reference guide for the 1746-NR8 RTD/Resistance Input
Module. The manual:
• gives you an overview of system operation
• explains the procedures you need to install and wire the module at the
customer site
• provides ladder programming examples
• provides an application example of how this input module can be used
to control a process
1Publication 1746-UM003A-EN-P
Preface 2
Related Documentation
The following documents contain information that may be helpful to you as
you use Allen-Bradley SLC™ products. To obtain a copy of any of the
Allen-Bradley documents listed, contact your local Allen-Bradley office or
distributor.
ForRead this DocumentDocument Number
An overview of the SLC 500 family of productsSLC 500 System Overview1747-SO001A-US-P
A description on how to install and use your Modular SLC 500
programmable controller
A description on how to install and use your Fixed SLC 500
programmable controller
A reference manual that contains status file data, instruction set,
and troubleshooting information about APS
A procedural and reference manual for technical personnel who use
an HHT to develop control applications
An introduction to HHT for first-time users, containing basic concepts
but focusing on simple tasks and exercises, and allowing the reader
to begin programming in the shortest time possible
A resource manual and user’s guide containing information about the
analog modules used in your SLC 500 system.
In-depth information on grounding and wiring Allen-Bradley
programmable controllers
A description of important differences between solid-state
programmable controller products and hard-wired electromechanical
devices
A complete listing of current Allen-Bradley documentation, including
ordering instructions. Also indicates whether the documents are
available on CD-ROM or in multi-languages.
A glossary of industrial automation terms and abbreviationsAllen-Bradley Industrial Automation Glossary AG-7.1
An article on wire sizes and types for grounding electrical equipment National Electrical CodePublished by the
Installation and Operation Manual for
Modular Hardware Style Programmable
Controllers
Installation & Operation Manual for Fixed
Hardware Style Programmable Controllers
SLC 500
and MicroLogix™ 1000 Instruction
Set Reference Manual
Allen-Bradley Hand-Held Terminal User’s
Manual
Getting Started Guide for HHT1747-NM009
SLC 500 Analog I/O Modules User’s Manual1746-6.4
Allen-Bradley Programmable Controller
Grounding and Wiring Guidelines
Application Considerations for Solid-State
Controls
Allen-Bradley Publication IndexSD499
1747-6.2
1747-6.21
1747-6.15
1747-NP002
1770-4.1
SGI-1.1
National Fire
Protection
Association of
Boston, MA.
Publication 1746-UM003A-EN-P
Preface 3
Common Techniques Used
in this Manual
Rockwell Automation
Support
The following conventions are used throughout this manual:
• Bulleted lists such as this one provide information, not procedural steps.
• Numbered lists provide sequential steps or hierarchical information.
• Italic type is used for emphasis.
Rockwell Automation offers support services worldwide, with over 75 Sales/
Support Offices, 512 authorized Distributors and 260 authorized Systems
Integrators located throughout the United States alone, plus Rockwell
Automation representatives in every major country in the world.
Local Product Support
Contact your local Rockwell Automation representative for:
• sales and order support
• product technical training
• warranty support
• support service agreements
Technical Product Assistance
If you need to contact Rockwell Automation for technical assistance, please
review the information in the Module Diagnostics and Troubleshooting chapter
first. Then call your local Rockwell Automation representative.
Your Questions or Comments on this Manual
If you have any suggestions for how this manual could be made more useful to
you, please contact us at the address below:
Rockwell Automation
Control and Information Group
Technical Communication, Dept. A602V
P.O. Box 2086
Milwaukee, WI 53201-2086
Publication 1746-UM003A-EN-P
Preface 4
Publication 1746-UM003A-EN-P
Overview
Chapter
1
Description
This chapter describes the 8-channel 1746-NR8 RTD/Resistance Input
Module
Module and explains how the SLC controller gathers RTD (Resistance
Module Module
Temperature Detector) temperature or resistance-initiated analog input from
the module. Included is:
• a general description of the module’s hardware and software features
• an overview of system operation
For the rest of the manual, the 1746-NR8 RTD/Resistance Input Module
referred to as simply the RTD module
The RTD module receives and stores digitally converted analog data from
RTDs or other resistance inputs such as potentiometers into its image table for
retrieval by all fixed and modular SLC 500 processors. An RTD consists of a
temperature-sensing element connected by 2, 3, or 4 wires that provide input
to the RTD module. The module supports connections from any combination
of up to eight RTDs of various types (for example: platinum, nickel, copper, or
nickel-iron) or other resistance inputs.
The RTD module supplies a small current to each RTD connected to the
module inputs (up to 8 input channels). The module provides on-board
scaling and converts RTD input to temperature (
input in ohms.
Each input channel is individually configurable for a specific input device.
Broken sensor detection (open- or short-circuit) is provided for each input
channel. In addition, the module provides indication if the input signal is
out-of-range. For more detail on module functionality, refer to the subsection
entitled System Overview
1Publication 1746-UM003A-EN-P
System Overview later in this chapter.
System OverviewSystem Overview
1-2 Overview
Figure 1.1 Simplified RTD Module Circuit
Constant Current Source
Ic=0.25 or
1.0 mA
RTD
Sense
RTD Module
Backplane
RTD 0
RTD 1
RTD 2
RTD 3
RTD 4
Return
RTD
Sense
Return
RTD
Sense
Return
RTD
Sense
Return
RTD
Sense
Return
A/D
Conversion
Digital Data
Digital
µP Circuit
Digital Data
Publication 1746-UM003A-EN-P
RTD 5
RTD 6
RTD 7
RTD
Sense
Return
RTD
Sense
Return
RTD
Sense
Return
Overview 1-3
RTD Compatibility
The following table lists the RTD types used with the RTD module and gives
each type’s associated temperature range, resolution, and repeatability
specifications. The next table shows the accuracy and temperature drift
specifications for the RTDs.
Table 1.1 RTD Temperature Ranges, Resolution, and Repeatability
Input TypeTemp. Range
(0.25 mA Excitation)
Platinum (385)
(2)
100Ω-200°C to +850°C
(-328°F to +1562°F)
200Ω-200°C to +850°C
(-328°F to +1562°F)
Ω-200°C to +850°C
500
(-328°F to +1562°F)
Ω-200°C to +850°C
1000
(-328°F to +1562°F)
Platinum (3916)
(2)
100Ω-200°C to +630°C
(-328°F to +1166°F)
Ω-200°C to +630°C
200
(-328°F to +1166°F)
Ω-200°C to +630°C
500
(-328°F to +1166°F)
1000Ω-200°C to +630°C
(-328°F to +1166°F)
Copper (426)
(2) (3)
10Ω-100°C to +260°C
(-328°F to +500°F)
Nickel (618)
(2) (4)
120Ω-100°C to +260°C
(-328°F to +500°F)
Nickel (672)
(2)
120Ω-80°C to +260°C
(-328°F to +500°F)
Nickel Iron (518)
(2)
604Ω-200°C to +200°C
(-328°F to +392°F)
(1) The temperature range for the 1000Ω, 500Ω, and 604Ω RTD is dependent on the excitation current.
(2) The digits following the RTD type represent the tem perature coefficient of resistance (α), which is defined as the resistance change per ohm per C. For instance, Platinum
385 refers to a platinum RTD with α = 0.00385 ohms/ohm · C or simply 0.00385 / C.
(3) Actual value at 0 C is 9.042Ω per SAMA standard RC21-4-1966.
(4) Actual value at 0 C is 100Ω per DIN standard.
Temp. Range
(1)
(1.0 mA Excitation)
-200°C to +850°C
(-328°F to +1562°F)
-200°C to +850°C
(-328°F to +1562°F)
-200°C to +390°C
(-328°F to +698°F)
-200°C to +50°C
(-328°F to +122°F)
-200°C to +630°C
(-328°F to +1166°F)
-200°C to +630°C
(-328°F to +1166°F)
-200°C to +380°C
(-328°F to +698°F)
-200°C to +50°C
(-328°F to +122°F)
-100°C to +260°C
(-328°F to +500°F)
-100°C to +260°C
(-328°F to +500°F)
-80°C to +260°C
(-328°F to +500°F)
-200°C to +180°C
(-328°F to +338°F)
(1)
0.1°C
(0.1°F)
0.1°C
(0.1°F)
0.1°C
(0.1°F)
0.1°C
(0.1°F)
0.1°C
(0.1°F)
0.1°C
(0.1°F)
0.1°C
(0.1°F)
0.1°C
(0.1°F)
0.1°C
(0.1°F)
0.1°C
(0.1°F)
0.1°C
(0.1°F)
0.1°C
(0.1°F)
(28 Hz, 50/60 Hz)
± 0.2°C
(± 0.4°F)
± 0.2°C
(± 0.4°F)
± 0.2°C
(± 0.4°F)
± 0.2°C
(± 0.4°F)
± 0.2°C
(± 0.4°F)
± 0.2°C
(± 0.4°F)
± 0.2°C
(± 0.4°F)
± 0.2°C
(± 0.4°F)
± 0.2°C
(± 0.4°F)
± 0.1°C
(± 0.2°F)
± 0.1°C
(± 0.2°F)
± 0.1°C
(± 0.2°F)
ResolutionRepeatability
IMPORTANT
The exact signal range valid for each input type is
dependent upon the excitation current magnitude that you
select when configuring the module. For details on
excitation current, refer to Appendix A.
Publication 1746-UM003A-EN-P
1-4 Overview
Table 1.2 RTD Accuracy and Temperature Drift Specifications
The table below lists the resistance input types you can use with the RTD
module and gives each type’s associated specifications.
Table 1.3 Resistance Input Specifications
Input TypeResistance Range
(0.25 mA Excitation)
Resistance 150
(1) The accuracy values assume that the module was calibrated within the specified temperature range of 0°C to 60°C (32°F to 140°F).
(2) The accuracy for 150
(3) The temperature drift for 150
Ω0Ω to 150Ω0Ω to 150Ω
500Ω0Ω to 500Ω0Ω to 500Ω 0.5Ω± 0.012Ω/°C
1000Ω0Ω to 1000Ω0Ω to 1000Ω 1.0Ω 0.025Ω/ C
3000Ω0Ω to 3000Ω0Ω to 1200Ω
Ω is dependent on the excitation current: 0.2 Ω at 0.25 mA and 0.15Ω at 1.0 mA
Ω is dependent on the excitation current: 0.006Ω/°C at 0.25 mA and 0.004Ω at 1.0 mA
Resistance Range
(1.0 mA Excitation)
Accuracy
(2)
1.5Ω
(1)
Temperature
Drift
±0.004Ω/°C
(±0.002
(± 0.007
(
0.014Ω/ F)
(
0.023Ω/ F)
Ω/°F)
Ω/°F)
0.040Ω/ C
(3)
Overview 1-5
Resolution Repeatability
0.01Ω 0.04Ω
Ω 0.2Ω
0.1
Ω 0.2Ω
0.1
Ω 0.2Ω
0.1
Hardware Overview
The RTD module occupies one slot in an SLC 500:
• modular system, except the processor slot (0)
• fixed system expansion chassis (1746-A2)
The module uses eight input words and eight output words for Class 1 and 16
input words and 24 output words for Class 3.
IMPORTANT
As shown in the illustration below and table that follows, the module contains
a removable terminal block (item 3) providing connection for any mix of eight
RTD sensors or resistance input devices. There are no output channels on the
module. Module configuration is done via the user program. There are no DIP
switches.
If the RTD module resides in a remote configuration with a
SLC 500 Remote I/O Adapter Module (1747-ASB), use
block transfer for configuration and data retrieval. Block
transfer requires a 1747-SN Remote I/O Scanner (Series B)
or PLC
®
processor.
Publication 1746-UM003A-EN-P
1-6 Overview
1
2
3
INPUT
CHANNELSTATUS
MODULE
RTD/resistance
04123
567
Figure 1.2 RTD Module Hardware
5
RTD 0
Sense 0
Return 0
RTD 1
Sense 1
Return 1
RTD 2
Sense 2
Return 2
RTD 3
Sense 3
Return 3
RTD 4
Sense 4
Return 4
RTD 5
Sense 5
Return 5
RTD 6
Sense 6
Return 6
RTD 7
Sense 7
Return 7
1746-NR8
6
WIN(21) 1G0AA2ZT
1746-NR8A 1.00
(21) 1G0AA2ZT
SLC 500
RTD / resistance INPUT MODULE
FRNSERCAT
U
®
L
CL I, DIV2 GP ABCD
IND CONT EQ.
FOR HAZ LOC
LISTED
1P00
55mA @ 24VDC, 100mA @ 5VDC
BACKPLANE REQUIREMENTS:
MADE IN U.S.A
C
U
®
L
SC P/N: 9060018-01
SC S/N: 167076
SC MFD: 0020
RESISTANCE (OHMS):
150, 500, 1000, 3000
NICKEL, NICKEL - IRON
RTD TYPES:
PLATINUM, COPPER
INPUT SIGNAL RANGES
150
4
7
Table 1.4 Hardware Features
ItemDescriptionFunction
1Channel Status LED
Indicators (green)
Displays operating and fault status of
channels 0, 1, 2, 3, 4, 5, 6, and 7
2Module Status LED (green)Displays module operating and fault status
3Removable Terminal BlockProvides physical connection to input devices
(Catalog # 1746-RT35)
4Cable Tie SlotsSecures wiring from module
5Door LabelProvides terminal identification
6Side Label (Nameplate)Provides module information
7Self-Locking TabsSecures module in chassis slot
General Diagnostic Features
The RTD module contains diagnostic features that can be used to help you
identify the source of problems that may occur during power up or during
normal channel operation. These power-up and channel diagnostics are
explained in Chapter 6, Module Diagnostics and Troubleshooting.
Publication 1746-UM003A-EN-P
The RTD module communicates to the SLC 500 processor through the
parallel backplane interface and receives +5V dc and +24V dc power from the
SLC 500 power supply through the backplane. No external power supply is
required. You may install as many RTD modules in your system as the power
supply can support, as shown in the illustration below.
Overview 1-7
System Overview
Figure 1.3 RTD Configuration
RTD Modules
SLC Processor
Each individual channel on the RTD module can receive input signals from 2,
3 or 4-wire RTD sensors or from resistance input devices. You configure each
channel to accept either input. When configured for RTD input types, the
module converts the RTD readings into linearized, digital temperature
readings in °C or °F. When configured for resistance inputs, the module
provides a linear resistance value in ohms.
IMPORTANT
The RTD module is designed to accept input from RTD
sensors with up to 3 wires. When using 4-wire RTD
sensors, one of the 2 lead compensation wires is not used
and the 4-wire sensor is treated like a 3-wire sensor. Lead
wire compensation is provided via the third wire. Refer
to Wiring Considerations on page 2-8 for more
information.
System Operation
The RTD module has 3 operational states:
• power-up
• module operation
• error (module error and channel error)
Publication 1746-UM003A-EN-P
1-8 Overview
Power-up
At power-up, the RTD module checks its internal circuits, memory, and basic
functions via hardware and software diagnostics. During this time, the module
status LED remains off, and the channel status LEDs are turned on. If no
faults are found during the power-up diagnostics, the module status LED is
turned on, and the channel status LEDs are turned off.
After power-up checks are complete, the RTD module waits for valid channel
configuration data from your SLC ladder logic program (channel status LEDs
off). After configuration data is written to one or more channel configuration
words and their channel enable bits are set by the user program, the channel
status LEDs go on and the module continuously converts the RTD or
resistance input to a value within the range you selected for the enabled
channels. The module is now operating in its normal state.
Each time a channel is read by the module, that data value is tested by the
module for a fault condition, for example, open-circuit, short-circuit, overrange, and under range. If such a condition is detected, a unique bit is set in
the channel status word and the channel status LED flashes, indicating a
channel error condition.
The SLC processor reads the converted RTD or resistance data from the
module at the end of the program scan or when commanded by the ladder
program. The processor and RTD module determine that the backplane data
transfer was made without error and the data is used in your ladder program.
Module Operation
Each input channel consists of an RTD connection, which provides:
• excitation current
• a sense connection, which detects lead-wire resistance
• a return connection, which reads the RTD or resistance value
Each of these analog inputs are multiplexed to an analog converter.
The A/D converter cycles between reading the RTD or resistance value, the
lead wire resistance, and the excitation current. From these readings, an
accurate temperature or resistance is returned to the user program.
The RTD module is isolated from the chassis backplane and chassis ground.
The isolation is limited to 500V ac. Optocouplers are used to communicate
across the isolation barrier. Channel-to-channel common-mode isolation is
limited to ± 5 volts.
LED Status
Publication 1746-UM003A-EN-P
The illustration below shows the RTD module LED panel consisting of nine
LEDs. The state of the LEDs (for example, off, on, or flashing) depends on the
operational state of the module (see table on page 1-9).
Overview 1-9
Figure 1.4 LED Indicators
INPUT
RTD Module
CHANNELSTATUS
MODULE
RTD/resistance
04123
567
The purpose of the LEDs is as follows:
• Channel Status - One LED for each of the 8 input channels indicates if the
channel is enabled, disabled, or is not operating as configured, due to an
error.
• Module Status - If OFF or flashing at any time, other than at powerup, this
LED indicates that non-recoverable module errors (for example, diagnostic
or operating errors) have occurred. The LED is ON if there are no module
errors.
The status of each LED, during each of the operational states (for example,
powerup, module operation and error), is depicted in the following table.
LED
Power-up
Ch 0 to 7 Status OnOn/Off
Mod. StatusOffOnFlashes/OffOn
(1) Module is disabled during powerup.
(2) Channel status LED is On if the respective channel is enabled and Off if the channel is disabled.
(3) Error if channel is enabled.
(1)
Module Operation
(No Error)
(2)
(3)
Off
Error
Flashes
Module Error Channel
Publication 1746-UM003A-EN-P
1-10 Overview
Module to Processor Communication
As shown in the following illustration, the RTD module communicates with
the SLC processor through the backplane of the chassis. The RTD module
transfers data to/receives data from the processor by means of an image table.
The image table consists of eight input words and eight output words when
configured for Class 1 operation; 16 input words and 24 output words when
configured for Class 3 operation. Data transmitted from the module to the
processor is called the input image (for example, Channel Data Words and
Channel Status Words). Conversely, data transmitted from the processor to the
module is called the output image (for example, Channel Configuration Words
and Scaling Limit Words). Details about the input and output images are
found in “Module Addressing” on page 3-2.
Figure 1.5 Communication Flow
Channel Data Words
RTD/Resistance
Analog Signals
1746-NR8
Input
Module
Channel Status Words
Scaling Limit Words
SLC 500
Processor
Channel Configuration Words
Chassis Backplane
The Channel Configuration Words (output image) contain user-defined
configuration information for the specified input channel. This information is
used by the module to configure and operate each channel. The Channel
Status Words (input image) contain status information about the channel’s
current configuration and operational state. The input data values of the
analog input channel are contained in the Channel Data Word (input image),
which is valid only when the channel is enabled and there are no channel errors
(for example, broken sensor or overrange.)
The user-set Scaling Limit Words (output image) provide a user-definable
scaling range for the temperature resistance data when using the proportional
counts data type.
Publication 1746-UM003A-EN-P
Chapter
2
Installation and Wiring
This chapter tells you how to:
• comply to European union directives
• avoid electrostatic damage
• determine the RTD module’s chassis power requirement
• choose a location for the RTD module in the SLC chassis
• install the RTD module
• wire the RTD module’s terminal block
This product is approved for installation within the European Union and EEA
regions. It has been designed and tested to meet the following directives.
Compliance to Europe
Union Directives
EMC Directive
This product is tested to meet Council Directive 89/336/EEC Electromagnetic
Compatibility (EMC) and the following standards, in whole or in part,
documented in a technical construction file:
• EN 50081-2
EMC - Generic Emission Standard, Part 2 - Industrial Environment
• EN 50082-2
EMC - Generic Immunity Standard, Part 2 - Industrial Environment
This product is intended for use in an industrial environment.
1Publication 1746-UM003A-EN-P
2-2 Installation and Wiring
Safety Considerations
Electrostatic Damage
Electrostatic discharge can damage semiconductor devices inside this module if
you touch backplane connector pins or other sensitive areas. Guard against
electrostatic damage by observing the precautions listed next.
ATTENTION
!!!!
Electrostatic discharge can degrade performance or cause
permanent damage. Handle the module as stated below.
• Wear an approved wrist strap grounding device when
handling the module.
• Touch a grounded object to rid yourself of electrostatic
charge before handling the module.
• Handle the module from the front, away from the
backplane connector. Do not touch backplane connector
pins.
• Keep the module in its static-shield bag when not in use, or
• Substitution of components may impair suitability for
Class I, Division 2.
• Do not replace components or disconnect equipment
unless power has been switched off.
• Do not connect or disconnect components unless power
has been switched off.
• All wiring must comply with N.E.C. article 501-4(b).
Publication 1746-UM003A-EN-P
Installation and Wiring 2-3
Power Requirements
The RTD module receives its power through the SLC500 chassis backplane
from the fixed or modular +5V dc/+24V dc chassis power supply. The
maximum current drawn by the module is shown in the table below.
5V dc24V dc
0.100A0.055A
When you are using a modular system configuration, add the values shown in
the table above to the requirements of all other modules in the SLC chassis to
prevent overloading the chassis power supply.
When you are using a fixed system controller, refer to the Important note about
module compatibility in a 2-slot expansion chassis on page 2-4.
Publication 1746-UM003A-EN-P
2-4 Installation and Wiring
Module Location in Chassis
Fixed Controller Compatibility Table
NR8 5V dc24V dc
IA4• 0.035IA8• 0.050IA16• 0.085IM4• 0.035IM8• 0.050IM16• 0.085OA8•0.185OA160.370OAP120.370IB8•0.050IB16•0.085IB32•0.050ITB16•0.085IV8•0.050IV16•0.085IV32•0.085ITV16•0.085IC16•0.085IG16• 0.140IH16• 0.085OB8• 0.135OB16• 0.280OB32 Series D or later • 0.190OB16E• 0.135OBP8• 0.135OBP16• 0.250OG16• 0.180OVP16• 0.250OV8• 0.135OV16•0.270OV32 Series D or later • 0.190IN16• 0.085OW4•0.0450.045
OW8•0.0850.090
OW160.1700.180
OX8• 0.0850.090
IO4• 0.0300.025
IO8• 0.0600.045
IO12•0.0900.070
NI4• 0.0250.085
NI80.2000.100
NI16I•0.1250.075
NI16V• 0.1250.075
NIO4I0.0550.145
NIO4V•0.0550.115
FIO4I•0.0550.150
FIO4V• 0.0550.120
NO4I0.0550.195
NO4V0.0550.195
NT4• 0.0600.040
NT8• 0.1200.070
INT4• 0.1100.085
NR4•0.0500.050
HSCE• 0.320HSCE2• 0.250BAS•0.1500.040
BASn• 0.1500.125
KE• 0.1500.040
KEn•0.1500.145
HS• 0.300HSTP1• 0.200-
Modular Chassis Considerations
Place your RTD module in any slot of an SLC 500 modular chassis (except slot
0) or a modular expansion chassis. Slot 0 is reserved for the modular processor
or adapter modules.
Fixed Expansion Chassis Considerations
IMPORTANT
IMPORTANT
The 2-slot, SLC 500 fixed I/O expansion chassis (1746-A2)
supports only specific combinations of modules. If you are
using the RTD module in a 2-slot expansion chassis with
another SLC I/O or communication module, refer to the
table at the left to determine whether the combination can
be supported.
When using the table, be aware that there are certain
conditions that affect the compatibility characteristics of
the BASIC module (BAS) and the DH-485/RS-232C
module (KE).
When you use the BAS module or the KE module to
supply power to a 1747-AIC Link Coupler, the link coupler
draws its power through the module. The higher current
drawn by the AIC at 24V dc is calculated and recorded in
the table for the modules identified as BASn (BAS
networked) or KEn (KE networked). Make sure to refer to
these modules if your application uses the BAS or KE
module in this way.
Publication 1746-UM003A-EN-P
Installation and Wiring 2-5
General Considerations
Most applications require installation in an industrial enclosure to reduce the
effects of electrical interference. RTD inputs are susceptible to electrical noises
due to the small amplitudes of their signal.
Group your modules to minimize adverse effects from radiated electrical noise
and heat. Consider the following conditions when selecting a slot for the RTD
module. Position the module in a slot:
• away from power lines, load lines and other sources of electrical noise such
as hard-contact switches, relays, and AC motor drives
• away from modules which generate significant radiated heat, such as the
32-point I/O modules
Module Installation and
Removal
When installing the module in a chassis, it is not necessary to remove the
terminal block from the module. However, if the terminal block is removed,
use the write-on label located on the side of the terminal block, as shown
below, to identify the module location and type.
SLOT
____
MODULE
RACK
____
_______________
Publication 1746-UM003A-EN-P
2-6 Installation and Wiring
Removing the Terminal Block
ATTENTION
Never install, remove, or wire modules with power applied
to the chassis or devices wired to the module. To avoid
cracking the removable terminal block, alternate the
removal of the slotted terminal block release screws.
!!!!
1.
1. Loosen the two terminal block release screws.
1.1.
Ter m inal B l ock
Release Screw
(Requires a 0.100 in
slot screwdriver.)
Publication 1746-UM003A-EN-P
Maximum Torque = 0.25 Nm (2.25 in-lbs)
2.
2. Grasp the terminal block at the top and bottom and pull outward and
2.2.
down.
Installation and Wiring 2-7
Installing the Module
1.
1. Align the circuit board of the RTD module with the card guides located at
1.1.
the top and bottom of the chassis, as shown in the following illustration.
Top and Bottom
Module Releases
Card
Guide
2.
2. Slide the module into the chassis until both top and bottom retaining clips
2.2.
are secured. Apply firm even pressure on the module to attach it to its
backplane connector. Never force the module into the slot.
3.
3. Cover all unused slots with the Card Slot Filler, Catalog Number 1746-N2.
3.3.
Removing the Module
1.
1. Press the releases at the top and bottom of the module and slide the module
1.1.
out of the chassis slot.
2.
2. Cover all unused slots with the Card Slot Filler, Catalog Number 1746-N2.
2.2.
The RTD module contains an 24-position, removable terminal block. The
terminal pin-out is shown in the illustration on page 2-8.
Publication 1746-UM003A-EN-P
2-8 Installation and Wiring
Terminal Wiring
ATTENTION
Disconnect power to the SLC before attempting to install,
remove, or wire the removable terminal wiring block. To
avoid cracking the removable terminal block, alternate the
removal of the terminal block release screws.
!!!!
Figure 2.1 Terminal Block
(Terminal Block Spare Part Number 1746-RT35)
RTD 0
Sense 0
Return 0
RTD 1
Sense 1
Return 1
RTD 2
Sense 2
Return 2
RTD 3
Sense 3
Return 3
RTD 4
Sense 4
Return 4
RTD 5
Sense 5
Return 5
RTD 6
Sense 6
Return 6
RTD 7
Sense 7
Return 7
Publication 1746-UM003A-EN-P
Release Screw Maximum Torque = 0.25 Nm (2.25 lbs-in)
Wiring Considerations
Follow the guidelines below when planning your system wiring.
Since the operating principle of the RTD module is based on the measurement
of resistance, take special care in selecting your input cable. For 2-wire or
3-wire configuration, select a cable that has a consistent impedance throughout
its entire length.
ConfigurationRecommended Cable
2-wireBelden™ #9501 or equivalent
3-wire
less than 30.48m (100 ft.)
3-wire
greater than 30.48 m (100 ft.) or high humidity
conditions
Belden #9533 or equivalent
Belden #83503 or equivalent
Installation and Wiring 2-9
For a 3-wire configuration, the module can compensate for a maximum cable
length associated with an overall cable impedance of 25 ohms.
IMPORTANT
Details of cable specifications are shown on page A-5.
Three configurations of RTDs can be connected to the RTD module, namely:
• 2-wire RTD, which is composed of 2 RTD lead wires (RTD and Return)
• 3-wire RTD, which is composed of a Sense and 2 RTD lead wires (RTD and
Return)
• 4-wire RTD, which is composed of 2 Sense and 2 RTD lead wires (RTD
and Return). The second sense wire of a 4-wire RTD is left open. It does not
matter which sense wire is left open.
IMPORTANT
The RTD module requires three wires to compensate for
lead resistance error. We recommend that you do not use
2-wire RTDs if long cable runs are required, as it reduces
the accuracy of the system. However, if a 2-wire
configuration is required, reduce the effect of the lead wire
resistance by using a lower gauge wire for the cable (for
example, use AWG #16 instead of AWG #24). Also, use
cable that has a lower resistance per foot of wire. The
module’s terminal block accepts one AWG #14 gauge wire.
($$)
•
To limit overall cable impedance, keep input cables as short as possible.
Locate your I/O chassis as near the RTD sensors as your application permits.
• Ground the shield drain wire at one end only. The preferred location is at
the chassis mounting tab of the rack, under the RTD module. Refer to IEEE
Std. 518, Section 6.4.2.7 or contact your sensor manufacturer for additional
details.
• Route RTD/resistance input wiring away from any high-voltage I/O wiring,
power lines, and load lines.
• Tighten terminal screws using a flat-head screwdriver. Each screw should be
turned tight enough to immobilize the wire’s end. Excessive tightening can
strip the terminal screw. The torque applied to each screw should not exceed
0.25 Nm (2.25 in-lbs) for each terminal.
• Follow system grounding and wiring guidelines found in your SLC 500
Installation and Operation Manual, publication 1747-6.2.
Publication 1746-UM003A-EN-P
2-10 Installation and Wiring
Figure 2.2 RTD Connections to Terminal Block
2-Wire Interconnection
RTD
Return
Belden #9501 Shielded Cable
3-Wire Interconnection
RTD
Sense
Return
Belden #9533 Shielded Cable or
Belden #83503 Shielded Cable
4-Wire Interconnection
RTD
Sense
Return
Leave One Sensor Wire Open
Belden #9533 Shielded Cable or
Belden #83503 Shielded Cable
Cable Shield (Frame
Ground)
Cable Shield (Frame
Ground)
Cable Shield (Frame
Ground)
Add
jumper
RTD 0
Sense 0
Return 0
RTD 1
Sense 1
Return 1
RTD 2
Sense 2
Return2
RTD 0
Sense 0
Return 0
RTD 1
Sense 1
Return 1
RTD 2
Sense 2
Return2
RTD 0
Sense 0
Return 0
RTD 1
Sense 1
Return 1
RTD 2
Sense 2
Return2
RTD 0
Sense 0
Return 0
RTD 1
Sense 1
Return 1
RTD 2
Sense 2
Return2
RTD 3
Sense 3
Return 3
RTD 4
Sense 4
Return 4
RTD 5
Sense 5
Return 5
RTD 6
Sense 6
Return 6
RTD 7
Sense 7
Return 7
Publication 1746-UM003A-EN-P
When using a 3-wire configuration, the module compensates for resistance
error due to lead wire length. For example, in a 3-wire configuration, the
module reads the resistance due to the length of one of the wires and assumes
that the resistance of the other wire is equal. If the resistances of the individual
lead wires are much different, an error may exist. The closer the resistance
values are to each other, the greater the amount of error that is eliminated.
Installation and Wiring 2-11
IMPORTANT
To ensure temperature or resistance value accuracy, the
resistance difference of the cable lead wires must be equal to
or less than 0.01
Ω..
There are several ways to insure that the lead values match as closely as
possible. They are as follows:
• Keep lead resistance as small as possible and less than 25Ω.
• Use quality cable that has a small tolerance impedance rating.
• Use a heavy-gauge lead wire which has less resistance per foot.
Wiring Resistance Devices (Potentiometers) to the Module
Potentiometer wiring requires the same type of cable as that for the RTD
described in the previous subsection. Potentiometers can be connected to the
RTD module as a 2-wire connection or a 3-wire connection.
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2-12 Installation and Wiring
Figure 2.3 2-Wire Potentiometer Connections to Terminal Block
For details on wiring a potentiometer to the module, see
page 2-8.
RTD 0
Sense 0
Return 0
RTD 1
Sense 1
Return 1
RTD 2
Sense 2
Return 2
RTD 3
Sense 3
Return 3
RTD 4
Sense 4
Return 4
RTD 5
Sense 5
Return 5
RTD 6
Sense 6
Return 6
RTD 7
Sense 7
Return 7
Potentiometer
Belden #9501 Shielded Cable
Cable Shield
(Frame Ground)
Add Jumper
Potentiometer
Belden #9501 Shielded Cable
Potentiometer wiper arm can be connected to either the RTD or return terminal
depending on whether the user wants increasing or decreasing resistance.
RTD 0
Sense 0
Return 0
RTD 1
Sense 1
Cable Shield
(Frame Ground)
Add Jumper
Return 1
RTD 2
Sense 2
Return 2
RTD 3
Sense 3
Return 3
RTD 4
Sense 4
Return 4
RTD 5
Sense 5
Return 5
RTD 6
Sense 6
Return 6
RTD 7
Sense 7
Return 7
Publication 1746-UM003A-EN-P
Figure 2.4 3-Wire Potentiometer Connections to Terminal Block
For details on wiring a potentiometer to the
module, see page 2-8.
Run RTD and sense wires from module to
potentiometer and tie them to one point.
Installation and Wiring 2-13
Potentiometer
Belden #83503 or #9533 Shielded Cable
Potentiometer wiper arm can be connected to either the RTD or return terminal
depending on whether the user wants increasing or decreasing resistance.
Run RTD and sense wires from module to
potentiometer and tie them to one point.
Potentiometer
Belden #83503 or #9533 Shielded Cable
Cable Shield
(Frame Ground)
Cable Shield
(Frame Ground)
RTD 0
Sense 0
Return
RTD 1
Sense 1
Return 1
RTD 2
Sense 2
Return 2
RTD 0
Sense 0
Return
RTD 1
Sense 1
Return 1
RTD 2
Sense 2
Return 2
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2-14 Installation and Wiring
Wiring Input Devices to the Module
To wire your 1746-NR8 module, follow these steps as shown in the illustration
below:
1.
1. At each end of the cable, strip some casing to expose the individual wires.
1.1.
2.
2. Trim the signal wires to 5.08-cm (2-inch) lengths. Strip about 4.76 mm (3/
2.2.
16 inch) of insulation away to expose the end of the wire.
3.
3. At one end of the cable twist the drain wire and foil shield together, bend
3.3.
them away from the cable, and apply shrink wrap. Then earth ground at
the frame ground of the rack.
4.
4. At the other end of the cable, cut the drain wire and foil shield back to the
4.4.
cable and apply shrink wrap.
5.
5. Connect the signal wires to the 1746-NR8 terminal block and the input.
5.5.
6.
6. Repeat steps 1 through 5 for each channel on the 1746-NR8 module.
6.6.
Figure 2.5 Shielded Cable
2-Conductor Shielded Cable
(See step 4.)
Signal Wire
Signal Wire
Signal Wire
Signal Wire
Signal Wire
Drain Wire
Drain Wire
(See step 3.)
Foil Shield
3-Conductor Shielded Cable
Foil Shield
Signal Wire
Signal Wire
Signal Wire
Signal Wire
Signal Wire
Publication 1746-UM003A-EN-P
Installation and Wiring 2-15
Calibration
The accuracy of a system that uses the RTD module is determined by the
following:
• the accuracy of the RTD
• resistance mismatch of the cable wires that connect the RTD to the module
• the accuracy of the RTD module
For optimal performance at the customer site, the RTD module is calibrated at
the factory prior to shipment. In addition, an autocalibration feature further
ensures that the module performs to specification over the life of the product.
Factory Calibration
The 2-pin calibration connector, on the RTD module circuit board, is used for
factory setup only.
Autocalibration
When a channel becomes enabled, the module configures the channel and
performs an autocalibration on the module if the combination of input type
and excitation current are unique to that channel. Autocalibration performs
A/D conversions on the zero voltage and the full-scale voltage of the A/D
converter.
IMPORTANT
These conversions generate offset (zero reference) and full scale (span
reference) coefficients that are saved and used by the module to perform future
A/D conversions.
You can command your module to perform an autocalibration cycle once every
5 minutes by setting any channel’s calibration disable bit to 0. To disable
autocalibration, all channel’s calibration disable bits must be set to 1. You can
control the module’s autocalibration time by disabling autocalibration, and
then setting any channel’s calibration disable bit to 0, waiting at least one
module scan time and then resetting that channel’s calibration disable bit to 1.
Several scan cycles are required to perform an autocalibration (see page 3-10).
It is important to remember that during autocalibration the module is not
converting input data.
Channel calibration time is shown in “Channel
Autocalibration” on page 3-10.
Publication 1746-UM003A-EN-P
2-16 Installation and Wiring
TIP
To maintain system accuracy we recommend that you
periodically perform an autocalibration cycle, for example:
• whenever an event occurs that greatly changes the internal
temperature of the control cabinet, such as opening or
closing its door
• at a convenient time when the system is not making
product, such as during a shift change
An autocalibration programming example is provided on page 5-10.
Single-Point Calibration
Single-point calibration is an optional procedure that can be used to improve
the accuracy of the RTD module and cable combination to greater than
±0.2°C (when the RTD is operating at ±50°C of the calibration temperature).
The offset, determined by the single-point calibration, can be used to
compensate for inaccuracies in the RTD module and cable combination.
After single-point calibration is performed, additional calibrations only need to
be performed if the cable is disturbed or degraded. (RTD replacement should
not affect the accuracy of the procedure.) However, periodic autocalibrations
should be performed. Follow the steps below to perform a single-point
calibration:
1.
1. Cycle power to the SLC 500 chassis.
1.1.
2.
2. Select a calibration temperature that is near the control point (±10°C).
2.2.
3.
3. Determine the exact resistance (±0.01
3.3.
Ω) equivalent to the calibration
temperature by using a published temperature vs. resistance chart.
4.
4. Replace the RTD with the fixed-precision resistor. (We recommend you use
4.4.
a 2 ppm temperature coefficient resistor.)
5.
5. Use the RTD module to determine the temperature equivalent to the fixed
5.5.
precision resistor and cable combination.
6.
6. Calculate the offset value by subtracting the calculated calibration
6.6.
temperature from the measured temperature.
7.
7. Reconnect the RTD to the cable.
7.7.
8.
8. Use ladder logic to apply (subtract) the offset from the measured
8.8.
temperature to obtain corrected temperature.
Publication 1746-UM003A-EN-P
Chapter
Preliminary Operating Considerations
This chapter explains how the RTD module and the SLC processor
communicate through the module’s input and output image. It lists the
preliminary setup and operation required before the RTD module can
function in a 1746 I/O system. Topics discussed include how to:
• enter the module ID code
• address your RTD module
• select the proper input filter for each channel
• calculate the RTD module update time
• interpret the RTD module response to slot disabling
3
Module ID Code
The module identification code is a unique number encoded for each 1746
I/O module. The code defines for the processor the type of I/O or specialty
module residing in a specific slot in the 1746 chassis.
To manually enter the module ID code, select (other) from the list of modules
on the system I/O configuration display. The module ID code for the RTD
module is shown below:
Operating ClassID Code
Class 13508
Class 312708
No special I/O configuration information is required for Class 1. The module
ID code automatically assigns the correct number of input and output words.
For Class 3 the user must assign the correct number of input and output words
(16 and 24).
1Publication 1746-UM003A-EN-P
3-2 Preliminary Operating Considerations
Module Addressing
SLC 5/0X
Data Files
Slot e
Output Image
Slot e
Input Image
The memory map shown in the following illustration displays how the output
and input image tables are defined for the RTD module.
Figure 3.1 Class 1 Memory Map
Bit 0
Word 0
Word 1
Word 2
Word 3
Word 4
Word 5
Word 6
Word 7
Word 0
Word 1
Word 2
Word 3
Word 4
Word 5
Word 6
Word 7
Bit 0
Output
Scan
Input
Scan
Analog Input
Module
Image Table
Output Image
8 Words
Input Image
8 Words
Output
Image
Input
Image
Bit 15
Channel 0 Configuration Word
Channel 1 Configuration Word
Channel 2 Configuration Word
Channel 3 Configuration Word
Channel 4 Configuration Word
Channel 5 Configuration Word
Channel 6 Configuration Word
Channel 7 Configuration Word
Channel 0 Data Word
Channel 1 Data Word
Channel 2 Data Word
Channel 3 Data Word
Channel 4 Data Word
Channel 5 Data Word
Channel 6 Data Word
Channel 7 Data Word
Bit 15
Address
O:e.0
O:e.1
O:e.2
O:e.3
O:e.4
O:e.5
O:e.6
O:e.7
Address
I:e.0
I:e.1
I:e.2
I:e.3
I:e.4
I:e.5
I:e.6
I:e.7
Publication 1746-UM003A-EN-P
Figure 3.2 Class 3 Memory Map
Preliminary Operating Considerations 3-3
SLC 5/0X
Data Files
Slot e
Output Image
Slot e
Input Image
Output
Scan
Input
Scan
Analog Input
Module
Image Table
Output Image
24 Words
Input Image
16 Words
Output Image
Input Image
Bit 15
Channel 0 Configuration Word
Channel 1 Configuration Word
Channel 2 Configuration Word
Channel 3 Configuration Word
Channel 4 Configuration Word
Channel 5 Configuration Word
Channel 6 Configuration Word
Channel 7 Configuration Word
lower scale limit range 0
upper scale limit range 0
lower scale limit range 1
upper scale limit range 1
lower scale limit range 2
upper scale limit range 2
lower scale limit range 3
upper scale limit range 3
lower scale limit range 4
upper scale limit range 4
lower scale limit range 5
upper scale limit range 5
lower scale limit range 6
upper scale limit range 6
lower scale limit range 7
upper scale limit range 7
Channel 0 Data Word
Channel 1 Data Word
Channel 2 Data Word
Channel 3 Data Word
Channel 4 Data Word
Channel 5 Data Word
Channel 6 Data Word
Channel 7 Data Word
Channel 0 Status Word
Channel 1 Status Word
Channel 2 Status Word
Channel 3 Status Word
Channel 4 Status Word
Channel 5 Status Word
Channel 6 Status Word
Channel 7 Status Word
Bit 15Bit 0
Bit 0
Word 0
Word 1
Word 2
Word 3
Word 4
Word 5
Word 6
Word 7
Word 8
Word 9
Word 10
Word 11
Word 12
Word 13
Word 14
Word 15
Word 16
Word 17
Word 18
Word 19
Word 20
Word 21
Word 22
Word 23
Word 0
Word 1
Word 2
Word 3
Word 4
Word 5
Word 6
Word 7
Word 8
Word 9
Word 10
Word 11
Word 12
Word 13
Word 14
Word 15
The RTD module output image (defined as the output from the CPU to the
RTD module) contains information that you configure to define the way a
specific channel on the RTD module works. The 1746-NR8 uses an 8-word
output image when operating in a Class 1 mode and 24-word output image
when operating in Class 3 mode. These words take the place of configuration
DIP switches on the module. Output words 0 through 7 are used to define the
operation of the module; output words 8 through 23 are used for special
user-set scaling using the proportional counts data format. Each output word 0
through 7 configures a single channel.
Example - If you want to configure channel 2 on the RTD module located in
slot 4 in the SLC chassis, your address would be O:4.2.
File Type
Element
Delimiter
O : 4 . 2
Slot
Word
Word
Delimiter
Chapter 4 gives you detailed bit information about the data content of the
configuration word.
Input Image - Data Words and Status Words
The 8-word RTD module input image (defined as the input from the RTD
module to the CPU) represents data words and status words.
Input words 0 through 7 (data words) hold the input data that represent the
temperature value of the RTD input or ohmic value of the resistance inputs for
channels 0 through 7. This data word is valid only when the channel is enabled
and there are no channel errors.
When operating in Class 3 mode, input words 8 through 15 (status words)
contain the status of channels 0 through 7 respectively. The status bits for a
particular channel reflect the configuration settings that you have entered into
the output image configuration word for that channel and provide information
about the channel’s operational state. To receive valid status information, the
channel must be enabled and the channel must have processed any
configuration changes that may have been made to the configuration word.
Publication 1746-UM003A-EN-P
Preliminary Operating Considerations 3-5
Example - To obtain the status of channel 2 (input word 6) of the RTD
module located in slot 3 in the SLC chassis, use address I:3.6.
Channel Filter Frequency
Selection
File Type
Slot
Word
I : 3 . 6
Element Delimiter
Word Delimiter
Chapter 4 gives you detailed bit information about the content of the data
word and the status word.
The RTD module uses a digital filter that provides noise rejection for the input
signals. The digital filter is programmable, allowing you to select from four
filter frequencies for each channel.
Selecting a low value (for example, 28 Hz) for the channel filter frequency
provides greater noise rejection for a channel, but also increases the channel
update time. Selecting a high value for the channel filter frequency provides
lesser noise rejection, but decreases the channel update time.
The Notch Frequencies table in the next section shows the available filter
frequencies, as well as the associated minimum normal mode rejection (NMR),
cut-off frequency, and step response for each filter frequency. The graphs on
page 3-8 and page 3-9 show the input channel frequency response for each
filter frequency selection.
1746-NR8 Channel Step Response
The channel filter frequency determines the channel’s step response. The step
response is the time required for the analog input signal to reach 100% of its
expected final value. This means that if an input signal changes faster than the
channel step response, a portion of that signal is attenuated by the channel
filter. The table below shows the step response for each filter frequency.
The effective resolution for an input channel depends upon the filter frequency
selected for that channel. The following table displays the effective resolution
for the various input types and filter frequencies:
Table 3.2 Effective Resolution for RTD and Resistance Inputs
Input TypeFilter Frequency
(1) The digits following the RTD type represent the temperature coefficient of resistance (α), which is defined as
the resistance change per ohm per °C. For instance, Platinum 385 refers to a platinum RTD with α = 0.00385
ohms/ohm -°C or simply 0.00385 /°C.
± 0.1°C
(± 0.1°F)
± 0.1°C
(± 0.1°F)
± 0.1°C
(± 0.1°F)
± 0.1°C
(± 0.1°F)
± 0.1°C
(± 0.1°F)
± 0.1°C
(± 0.1°F)
± 0.1°C
(± 0.1°F)
± 0.1°C
(± 0.1°F)
± 0.1°C
(± 0.2°F)
± 0.1°C
(± 0.1°F)
± 0.1°C
(± 0.1°F)
± 0.1°C
(± 0.1°F)
± 0.2°C
(± 0.4°F)
± 0.2°C
(± 0.4°F)
± 0.2°C
(± 0.4°F)
± 0.2°C
(± 0.4°F)
± 0.2°C
(± 0.4°F)
± 0.2°C
(± 0.4°F)
± 0.2°C
(± 0.4°F)
± 0.2°C
(± 0.4°F)
± 0.4°C
(± 0.7°F)
± 0.1°C
(± 0.1°F)
± 0.1°C
(± 0.1°F)
± 0.1°C
(± 0.1°F)
± 0.8°C
(± 1.4°F)
± 0.8°C
(± 1.4°F)
± 0.8°C
(± 1.4°F)
± 0.8°C
(± 1.4°F)
± 0.8°C
(± 1.4°F)
± 0.8°C
(± 1.4°F)
± 0.8°C
(± 1.4°F)
± 0.8°C
(± 1.4°F)
± 1.0°C
(± 1.8°F)
± 0.3°C
(± 0.5°F)
± 0.3°C
(± 0.5°F)
± 0.3°C
(± 0.5°F)
Publication 1746-UM003A-EN-P
(2) Actual value at 0°C is 9.042
(3) Actual value at 0°C is 100
Ω per SAMA standard RC21-4-1966.
Ω per DIN standard.
Preliminary Operating Considerations 3-7
Channel Cut-Off Frequency
The channel filter frequency selection determines a channel’s cut-off frequency,
also called the -3 dB frequency. The cut-off frequency is defined as the point
on the input channel frequency response curve where frequency components
of the input signal are passed with 3 dB of attenuation. All frequency
components at or below the cut-off frequency are passed by the digital filter
with less than 3 dB of attenuation. All frequency components above the cut-off
frequency are increasingly attenuated, as shown in the following illustrations.
The cut-off frequency for each input channel is defined by its filter frequency
selection. The table on page 3-5 shows the input channel cut-off frequency for
each filter frequency. Choose a filter frequency so that your fastest changing
signal is below that of the filter’s cut-off frequency. The cut-off frequency
should not be confused with update time. The cut-off frequency relates how
the digital filter attenuates frequency components of the input signal. The
update time defines the rate at which an input channel is scanned and its
channel data word updated. See page 3-10 for determining the channel update
time.
Figure 3.3 28 Hz Filter Frequency Response
Publication 1746-UM003A-EN-P
3-8 Preliminary Operating Considerations
Figure 3.4 50/60 Hz Filter Frequency Response
0881762643524405286167047928809681056
Figure 3.5 800 Hz Filter Frequency Response
Publication 1746-UM003A-EN-P
0272538804107013361602186821342400
Preliminary Operating Considerations 3-9
Figure 3.6 6400 Hz Filter Frequency Response
021364269640285351066812801149341706719200
This section shows how to determine the channel update time and channel
autocalibration time. In addition, the scanning process is briefly described.
The RTD module channel update time is defined as the time required for the
module to sample and convert (scan) the input signal of an enabled input
channel and make the resulting data value available to the SLC processor for
update.
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3-10 Preliminary Operating Considerations
Channel Autocalibration
Upon entry into the channel enabled state, the module configures that channel
and performs an autocalibration on the module if the combination of input
and excitation current are unique to that channel. Module calibration takes
precedence over channel scanning. Module calibration time is dependent on
the number of unique input type and excitation current combinations and is
equal to 510 msec +(125 msec x number of unique combinations).
Update Time and Scanning Process
The illustration on page 3-11 shows the scanning process for the RTD module
assuming that the module is running normally and more than one channel is
enabled. The scanning cycle is shown for the situation where channels 0 and 1
are enabled and channels 2 through 7 are not used.
Channel scan time is a function of the filter frequency, as shown in the
following table:
Table 3.3 Channel Scan Time
Filter Frequency
28 Hz125 ms250 ms
50/60 Hz75 ms147 ms
800 Hz10 ms18 ms
6400 Hz6 ms10 ms
(1) The module-scan time is obtained by summing up the channel-scan time for each enabled channel. For
example, if 3 channels are enabled with lead resistance and the 50/60 Hz filter is selected, the
module-scan time is 3 x 147 ms = 441 ms.
Channel Scan Time
(1)
With Lead Resistance
The fastest module update time occurs when only one channel with a 6400 Hz
filter frequency is enabled and lead resistance measurement is disabled.
Module Update Time = 6 ms
With 3 channels enabled, the module update time is:
3 channels x 6 ms/channel = 18 ms. The slowest module update time occurs
when eight channels, each using a 28 Hz filter frequency and with lead
resistance measurement always enabled.
Publication 1746-UM003A-EN-P
Module Update Time = 8 x 250 ms = 2000 ms
Figure 3.7 Scanning Cycle
Update Channel 1 Data Word
Calculate Channel 1 Data
Configure and Start Channel 0 A/D
Read Channel 1 A/D
Preliminary Operating Considerations 3-11
Channel 1Channel 0
Start
Wait for Channel 0 A/D Conversion
Read Channel 0 A/D Configure and
Start Channel 1 A/D
Wait for Channel 1 A/D ConversionCalculate Channel 0 Data
Update Channel 0 Data Word
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3-12 Preliminary Operating Considerations
The table below gives you the turn-on, turn-off, and reconfiguration times for
enabling or disabling a channel.
DescriptionDuration
Turn-On Time The time it takes to make converted data available in the
data word and to set the status bit (transition from 0 to
1) in the status word, after setting the enable bit in the
configuration word.
Turn-Off TimeThe time it takes to reset the status bit (transition from 1
to 0) in the status word and to zero the data word, after
resetting the enable bit in the configuration word.
Reconfiguration TimeThe time it takes to change a channel configuration if the
new device type and excitation current are a unique
combination. The enable bit remains in a steady state of
1. (Changing temperature/resistance units or data format
does not require reconfiguration time.)
By writing to the status file in your modular SLC processor you can disable any
chassis slot. Refer to your SLC programming manual for the slot disable/enable
procedure.
Requires up to one module update time plus 510 msec +
125 milliseconds x the number of unique input type and
excitation current combinations.
Requires up to one module update time.
Requires up to one module update time plus 510 msec +
125 milliseconds x the number of unique input type and
excitation current combinations.
Input Response
When an RTD slot is disabled, the RTD module continues to update its input
image table. However, the SLC processor does not read inputs from a module
that is disabled. Therefore, when the processor disables the RTD module slot,
the module inputs appearing in the processor input image remain in their last
state and the module’s updated image table is not read. When the processor
re-enables the module slot, the current state of the module inputs are read by
the processor during the subsequent scan.
Output Response
The SLC processor may change the RTD module output data (configuration)
as it appears in the processor output image. However, this data is not
transferred to the RTD module when the slot is disabled. The outputs are held
in their last state. When the slot is re-enabled, the data in the processor image
is transferred to the RTD module.
Publication 1746-UM003A-EN-P
Chapter
4
Channel Configuration, Data, and Status
This chapter examines the channel configuration word and the channel status
word bit by bit, and explains how the module uses configuration data and
generates status during operation. It gives you information about how to:
• configure a channel
• examine channel input data
• check a channel’s status
Channel Configuration
The channel configuration word is a part of the RTD module’s output image
as shown in the illustration below. Output words 0 through 7 correspond to
channels 0 through 7 on the module. Setting the condition of bits 0 through
15 in these words via your ladder logic program causes the channel to operate
as you choose (for example, RTD type, reading in °C). Output words 8
through 23 (Class 3 only) are used to further define the channel configuration
to allow you to choose a scaling format other than the module default when
using the proportional counts data format. You can use words 8 and 9 to define
a user-set range for channel 0, words 10 and 11 for channel 1, etc.
A bit-by-bit examination of the configuration word is provided in the table on
page 4-5. Programming is discussed in Chapter 5. Addressing is explained in
Chapter 3.
Module default settings for configuration words 0 through 7 are all zeros.
Scaling defaults are explained on page 4-9 under the explanation for the
User-set Scaling Select bits 13 and 14.
Channel Configuration
Procedure
The channel configuration word consists of bit fields, the settings of which
determine how the channel operates. This procedure looks at each bit field
separately and helps you configure a channel for operation. Refer to the table
on page 4-5 and the bit field descriptions that follow for complete
configuration information. See page B-1 for a configuration worksheet that
can assist your channel configuration.
Configure Each Channel
1.
1. Determine the input device type (RTD type or resistance input) for a
1.1.
channel and enter its respective 4-digit binary code in bit field 0-3 (Input
Type Selection) of the channel configuration word.
2.
2. Select a data format for the data word value. Your selection determines how
2.2.
the analog input value from the A/D converter is expressed in the data
word. Enter your 2-digit binary code in bit field 4 and 5 (Data Format
Selection) of the channel configuration word. If you have chosen
proportional counts data format, you may define the scaling range. The
default valves for the limit registers are 0. If the lower limit and the upper
limit are both 0, the module uses -32,768 as the lower limit and +32,767 as
the upper limit. If the lower limit is equal to the upper limit, a
configuration error occurs. Otherwise, the module uses limit values in these
registers. Make sure to enter the lower and upper limits in the scale limit
registers for that channel, if you want user-defined scaling. An example on
page 4-9 (user-set scaling) explains how to do this.
3.
3. Determine the desired state for the channel data word if a broken input
3.3.
condition is detected for that channel (open-circuit or short- circuit). Enter
the 2-digit binary code in bit field 6 and 7 (Broken Input Selection) of the
channel configuration word.
4.
4. If the channel is configured for RTD inputs and engineering units data
4.4.
format, determine if you want the channel data word to read in degrees
Fahrenheit or degrees Celsius and enter a one or a zero in bit 8
(Temperature Units) of the configuration word. If the channel is configured
for a resistance input, this field is ignored.
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4-4 Channel Configuration, Data, and Status
5.
5. Determine the desired input filter frequency for the channel and enter the
5.5.
2-digit binary code in bit field 9 and 10 (Filter Frequency Selection) of the
channel configuration word. A lower filter frequency increases the channel
update time, but also increases the noise rejection and channel resolution. A
higher filter frequency decreases the channel update time, but also decreases
the noise rejection and channel resolution.
6.
6. Determine which channels are used in your program and enable them.
6.6.
Place a one in bit 11 (channel Enable) if the channel is to be used. Place a
zero in bit 11 if the channel will not be used.
7.
7. Select the excitation current for the input channel. A zero in bit 12 provides
7.7.
an excitation current of 1.0 mA; a 1 provides 0.25 mA. Select the excitation
current value based on RTD vendor recommendations and the Input Specifications table, page A-2.
8.
8. Select the lead resistance measurement option. The module can disable lead
8.8.
resistance measurement, periodically measure the lead resistance, or
measure the lead resistance on each acquisition for each one of the 8
channels. Setting a channel’s lead-resistance enable bits to 00 disables the
lead resistance measurement. Setting a channel’s lead resistance enable bits
01 enables the periodic measurement of the lead resistance, which occurs
once every 5 minutes. Setting a channel’s lead resistance enable bits to 10
enables measurement of the lead resistance on each acquisition cycle.
9.
9. Build the channel configuration word using the configuration worksheet on
9.9.
page B-1 for every channel on each RTD module repeating the procedures
given in steps 1 through 9.
Enter the Configuration Data
Following the steps outlined in Chapter 5 (Ladder Programming Examples),
enter your configuration data into your ladder program and copy it to the
RTD module.
Publication 1746-UM003A-EN-P
Channel Configuration, Data, and Status 4-5
Table 4.1 Channel Configuration Word (O:e.0 through O:e.7) - Bit Definitions
DefineTo SelectMake these bit settings in the Channel Configuration Word
(1) Actual value at 0 °C is 9.042Ω per SAMA standard RC21-4-1966.
(2) Actual value at 0 °C is 100
(3) Values are in 0.1 degree /step or 0.1
(4) Values are in 1 degree /step or 1
Ω per DIN standard.
Ω/step for all resistance input types, except 150Ω. For the 150Ω resistance input type, the values are in 0.01Ω/step.
Ω/step for all resistance input types, except 150Ω. For the 150Ω resistance input type, the values are in 0.1Ω/step.
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4-6 Channel Configuration, Data, and Status
(5) This bit is ignored when a resistance device is selected.
Input Type Selection (Bits 0 through 3)
The input type bit field lets you configure the channel for the type of input
device you have connected to the module. Valid input devices are shown in the
previous table.
Data Format Selection (Bits 4 and 5)
The data format bit field lets you define the format for the channel data word
contained in the module input image. Valid data types are engineering units,
scaled-for-PID, and proportional counts. If you select proportional counts and
are operating in Class 3, you have the option of using user-defined scaling
(output registers O:8 through O:23). Unless you specify otherwise, the data is
scaled to the full scale range for that channel.
Table 4.2 Bit Descriptions for Data Format Select
Binary
Value
00engineering units x 1 Express values in 0.1 degree or 0.1
01engineering units x 10 Express values in 1 degree or 1
10scaled-for-PIDThe input signal range for the selected input type is its
11proportional countsThe input signal range is proportional to your selected
SelectDescription
Ω or 0.01Ω for 150Ω
pot., only
Ω or 0.1Ω for150Ω pot.,
only.
full scale input range. The signal range is scaled into a 0
to 16383 range, which is what the SLC processor expects
in the PID function.
input type and scaled into a -32768 to +32767 range
(default) or user-set range, based on the scale limit words
(O:e.8 to O:e.23)
Using Scaled-For-PID and Proportional Counts Formats
The RTD module provides eight options for displaying input channel data.
These are 0.1°F, 0.1°C, 1°F, 1°C, 0.1
Counts. The first six options represent real engineering units and do not
require explanation. The Scaled-for-PID selection allows you to directly
interface RTD Data into a PID instruction without intermediate scale
operations and Proportional Counts selection provides the highest display
resolution, but also require you to manually convert the channel data to real
Engineering Units.
Ω, 1Ω, Scaled-for-PID, and Proportional
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Channel Configuration, Data, and Status 4-7
Default scaling can be selected for scaled-for-PID data format and proportional
counts data format. User-set scaling can be defined for proportional counts data
format. For a description of default scaling, see page 4-7 (scaled-for-PID data
format) and page 4-8 (proportional counts data format). For a description of
user-set scaling using proportional counts data format, see page 4-9.
The equations on page 4-11 show how to convert from Scaled-for-PID to
Engineering Units, Engineering Units to Scaled-for-PID, Proportional Counts
to Engineering Units, and Engineering Units to Proportional Counts. To
perform the conversions, you must know the defined temperature or resistance
range for the channel’s input type. Refer to the Channel Data Word Format in
the tables on page 4-13 and page 4-14. The lowest possible value for an input
type is S
, and the highest possible value is S
LOW
HIGH
.
Scaled-for-PID - If the user selects scaled-for-PID as the data format, the data
word for that channel is a number between 0 and 16383. Zero (0) corresponds
to the lowest temperature value of the RTD type or the lowest resistance value
(ohms). The value 16383 corresponds to the highest temperature value for that
RTD or the highest resistance value (ohms). For example, if a 100
RTD (
α = 0.003916) is selected, then the relationship of temperature and
Ω Platinum
module counts is:
TemperatureCounts
-200°C0
+630°C16383
The following illustration shows the linear relationship between output counts
and temperature when one uses scaled-or-PID data format.
Figure 4.2 Linear Relationship Between Temperature and PID Counts
Counts
16383
°C
-200°C
630°C
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4-8 Channel Configuration, Data, and Status
Proportional Counts Data Format - If the user selects proportional counts data
format and uses the default limits of 0, the data word for that channel is a
number between -32,768 and +32,767. This provides the greatest resolution of
all scaling options. The value -32,768 corresponds to the lowest temperature
value of the RTD type or the lowest resistance value (ohms). The value 32,767
corresponds to the highest temperature value for that RTD or the highest
resistance value (ohms). For example, if a 100
Ω Platinum RTD (3916) is
selected, then the relationship of temperature and module counts is:
TemperatureCounts
-200°C-32768
+630°C+32767
The following illustration shows the linear relationship between output counts
and temperature when one uses proportional counts data format.
Figure 4.3 Linear Relationship Between Temperature and Proportional Counts
Counts
+32767
-200°C
°C
630°C
-32768
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Channel Configuration, Data, and Status 4-9
User-Set Scaling
Proportional Counts - If the user wants to configure the module to scale the
data word to something other than -32,768 to +32,767, the user defines what
the upper and lower limits are going to be. However, the maximum range
remains -32,768 to +32,767. The user defines what the upper and lower limits
are going to be by placing the range in the user-set scaling words for that
channel. The module scales the input data to the upper and lower limit in an
linear relationship. The following example clarifies this feature. In this
example, the RTD module channel that is configured for user-set scaling is
channel 3. As shown in the following illustration, the user has programmed the
channel 3 configuration word for 1000
proportional counts data format (bits 4 and 5): and configuration words 14
and 15 for scaling. The program for the following example is described on
page 5-4 in chapter 5.
Ω potentiometer (bits 0 to 3):
Configuration Word
Channel 3
Range
Channel 3
Lower scale limit set
for 3
Upper scale limit set
for 3
The user desires to control the line speed of a conveyor. A 1000
Ω
potentiometer is used to sense the conveyor line speed. The line speed varies
between 3 ft./minute (0 ohms) and 50 ft./minute (1000 ohms).
As shown in the illustration on below, the user selects a 1000
Ω potentiometer
as the input type. If the user chooses engineering units as the data format, the
module data word is a value between 0 and 1000 ohms. However, if the user
chooses the proportional counts data format and utilizes the user-set scaling
feature, the number 3 can be entered in O:e.14 and the number 50 in O:e.15.
In this situation, the RTD module returns a number between 3 and 50 in its
data word. This action saves the user time in ladder programming.
Figure 4.4 User-set Scaling Using Proportional Counts Data Format
Selected Proportional Counts Data Format
Ω Pot
O:e.3
O:e.14
O:e.15
Selected 1000
110000010000
0111
1100000000000000
0100110000000000
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4-10 Channel Configuration, Data, and Status
Configuration Words For User-set Scaling (Words 8 to 23)
The following illustration shows the address of the user-set limit scale words
used to define the lower value and the upper value of the user-set scale words.
You can use the words for a channel when proportional counts mode is selected
for that channel
Any time proportional counts is selected and the upper limit is not zero, but is
equal to the lower limit, a configuration error occurs. For example, if both
scaling limits are 0, or if the lower range value is greater than or equal to the
upper range value, a configuration error occurs.
Figure 4.5 Limit Scale Words
Channel 0
Channel 1
Channel 2
Channel 3
Channel 4
Channel 5
Channel 6
O:e.8
O:e.9
O:e.10
O:e.11
O:e.12
O:e.13
O:e.14
O:e.15
O:e.16
O:e.17
O:e.18
O:e.19
O:e.20
O:e.21
Defines lower scale limit for Ch 0
Defines upper scale limit for Ch 0
Defines lower scale limit for Ch 1
Defines upper scale limit for Ch 1
Defines lower scale limit for Ch 2
Defines upper scale limit for Ch 2
Defines lower scale limit for Ch 3
Defines upper scale limit for Ch 3
Defines lower scale limit for Ch 4
Defines upper scale limit for Ch 4
Defines lower scale limit for Ch 5
Defines upper scale limit for Ch 5
Defines lower scale limit for Ch 6
Defines upper scale limit for Ch 6
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Channel 7
O:e.22
O:e.23
Defines lower scale limit for Ch 7
Defines upper scale limit for Ch 7
Channel Configuration, Data, and Status 4-11
Scaling Examples
The following examples are using the default scaling ranges:
The following table shows the temperature ranges of several 1746-NR8 RTDs.
The table applies to both 0.25 and 1.0 mA excitation currents. The
temperature ranges of the remaining RTDs vary with excitation current, for
example, 1000
Ω Platinum 385, 1000Ω Platinum 3916, and 10Ω Copper 426.
Channel Configuration, Data, and Status 4-13
Table 4.3 Data Formats for RTD Temperature Ranges for 0.25 and 1.0 mA Excitation
Current
RTD Input TypeData Format
Engineering Units x 1Engineering Units x 10Scaled-for-PID Proportional Counts
0.1°C0.1°F1.0°C1.0°F
Ω Platinum (385)-2000 to +8500-3280 to +15620-200 to +850-328 to +1562 0 to 16383-32768 to 32767
100
Ω Platinum (385)-2000 to +6300-3280 to + 6300-200 to +630-328 to +6300 to 16383-32768 to 32767
200
Ω Platinum (3916)-2000 to +6300-3280 to +6300-200 to +630-328 to +6300 to 16383-32768 to 32767
100
Ω Platinum (3916)-2000 to +6300-3280 to +6300-200 to +630-328 to +6300 to 16383-32768 to 32767
200
Ω Nickel (672)-800 to +2600-3280 to +5000-80 to +260-328 to +5000 to 16383-32768 to 32767
120
(1)
Ω Nickel (618)
120
Ω Copper (426)-1000 to +2600-3280 to +5000-100 to +260-328 to +5000 to 16383-32768 to 32767
10
(1) Actual value at 0 °C is 100Ω per DIN standard.
-1000 to +2600-3280 to +5000-100 to +260-328 to +5000 to 16383-32768 to 32767
(Default)
Table 4.4 Data Format for 500
ΩΩΩΩ
Platinum RTD (385)
Excitation Current Data Format
Engineering Units x 1Engineering Units x 10Scaled-for-PID Proportional Counts
0.1
C0.1°F1.0°C1.0°F
(Default)
0.25 mA-2000 to +8500-3280 to +15620-200 to +850-328 to +1562 0 to 16383-32768 to 32767
1.0 mA-2000 to +3900-3280 to +6980-200 to +390-328 to +6980 to 16383-32768 to 32767
Table 4.5 Data Format for 1000
ΩΩΩΩ
Platinum RTD (385)
Excitation Current Data Format
Engineering Units x 1Engineering Units x 10Scaled-for-PID Proportional Counts
0.1
C0.1°F1.0°C1.0°F
(Default)
0.25 mA-2000 to +8500-3280 to +15620-200 to +850-328 to +1562 0 to 16383-32768 to 32767
1.0 mA-2000 to +500-3280 to +1220-200 to +50-328 to +1220 to 16383-32768 to 32767
Table 4.6 Data Format for 500
ΩΩΩΩ
Platinum RTD (3916)
Excitation Current Data Format
Engineering Units x 1Engineering Units x 10Scaled-for-PID Proportional Counts
0.1
C0.1°F1.0°C1.0°F
(Default)
0.25 mA-2000 to +6300-3280 to +11660-200 to +630-328 to +1166 0 to 16383-32768 to 32767
1.0 mA-2000 to +3800-3280 to +6980-200 to +380-328 to +6980 to 16383-32768 to 32767
Table 4.7 Data Format for 1000
ΩΩΩΩ
Platinum RTD (3916)
Excitation Current Data Format
Engineering Units x 1Engineering Units x 10Scaled-for-PID Proportional Counts
0.1
C0.1°F1.0°C1.0°F
(Default)
0.25 mA-2000 to +6300-3280 to +11660-200 to +630-328 to +1166 0 to 16383-32768 to 32767
1.0 mA-2000 to +500-3280 to +1220-200 to +50-328 to +1220 to 16383-32768 to 32767
Table 4.8 Data Format for 604
ΩΩΩΩ
Nickel Iron RTD (518)
Excitation Current Data Format
Engineering Units x 1Engineering Units x 10Scaled-for-PID Proportional Counts
0.1°C0.1°F1.0°C1.0°F
(Default)
0.25 mA-2000 to +2000-3280 to +3920-200 to +200-328 to +3920 to 16383-32768 to 32767
1.0 mA-2000 to +1800-3280 to +3380-200 to +180-328 to +3380 to 16383-32768 to 32767
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4-14 Channel Configuration, Data, and Status
The following tables show the resistance ranges provided by the 1746-NR8.
Table 4.9 Data Format for 150Ω
Ω Resistance Input
ΩΩ
Resistance Input TypeData Format
Engineering Units x 1Engineering Units x 10Scaled-for-PIDProportional Counts
0.01
(1)
Ω
0.1Ω
(1)
(Default)
150Ω0 to 150000 to 15000 to 16383-32768 to 32767
(1) When ohms are selected, the temperature-units selection (bit 8) is ignored.
Table 4.10 Data Format for 500
ΩΩΩΩ and 1000
ΩΩΩΩ
Resistance Input
Resistance Input TypeData Format
Engineering Units x 1Engineering Units x 10Scaled-for-PIDProportional Counts
0.1
(1)
Ω
1.0Ω
(1)
(Default)
500Ω0 to 50000 to 5000 to 16383-32768 to 32767
Ω0 to 100000 to 10000 to 16383-32768 to 32767
1000
(1) When ohms are selected, the temperature-units selection (bit 8) is ignored.
Table 4.11 Data Format for 3000
ΩΩΩΩ Resistance Input
Excitation CurrentData Format
Engineering Units x 1Engineering Units x 10Scaled-for-PIDProportional Counts
0.1
(1)
Ω
1.0 Ω
(1)
(Default)
0.25 mA0 to 300000 to 30000 to 16383-32768 to 32767
1.0 mA0 to 120000 to 12000 to 16383-32768 to 32767
(1) When ohms are selected, the temperature-units selection (bit 8) is ignored.
The following table shows the data resolution provided by the 1746-NR8 for
RTD input types using the various data formats. The table applies to both 0.25
and 1.0 mA excitation currents. The data resolution of the remaining RTDs
vary with excitation current.
Table 4.12 Channel Data Word Resolution for RTDs
RTD Input Type
Data Format (Bits 4 and 5)
Engineering Units x 1 Engineering Units x 10Scaled-for-PIDProportional Counts
The following two tables show the data resolution provided by the 1746-NR8
for resistance input types using the various data formats.
Table 4.18 Channel Data Word Resolution for 150Ω
Resistance
Input Type
Ω0.01Ω/step0.1Ω/step0.0092Ω/step0.0023Ω/step
150
Table 4.19 Channel Data Word Resolution for 500
Inputs
Resistance
Input Type
Ω0.1Ω/step1Ω/step0.0305Ω/step0.0076Ω/step
500
Ω0.1Ω/step1Ω/step0.0610Ω/step0.0153Ω/step
1000
Ω0.1Ω/step1Ω/step0.1831Ω/step0.0458Ω/step
3000
Data Format (Bits 4 and 5)
Engineering Units
x 1
OhmsOhmsOhmsOhms
Data Format (Bits 4 and 5)
Engineering Units
x 1
OhmsOhmsOhmsOhms
Engineering
Units x 10
Engineering
Units x 10
Ω Resistance Input
ΩΩ
Scaled-for-PID Proportional
Counts
(Default)
ΩΩΩΩ, 1000ΩΩΩΩ, and 3000ΩΩΩΩ Resistance
Scaled-for-PID Proportional
Counts
(Default)
Broken Input Selection (Bits 6 and 7)
The next table shows the descriptions for bits 6 and 7. The broken input bit
field lets you define the state of the channel data word when an open-circuit or
short-circuit condition is detected for that channel.
An open-circuit condition occurs when the RTD or potentiometer or its
extension wire is physically separated or opened. This can happen if the wire is
cut or disconnected from the terminal block.
The short-circuit condition applies only to RTD input types. This can happen
if the RTD or its signal wires are shorted together for any reason. The
short-circuit condition does not apply to resistance ranges since they start at 0
ohms, which can be a short-circuit condition.
Table 4.20 Bit Descriptions for Broken Input Selection
Binary
Value
00ZeroForce the channel data word to 0 during an open-circuit condition
01UpscaleForce the channel data word value to its full scale value during an
10Downscale Force the channel data word value to its low scale value during
SelectDescription
or short-circuit condition.
open-circuit or short-circuit condition. The full scale value is
determined by the input type, data format, and scaling selected.
an open-circuit or short-circuit condition. The low scale value is
determined by the input type, data format, and scaling selected.
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Channel Configuration, Data, and Status 4-17
Temperature Units Selection (Bit 8)
The following table shows the description for bit 8. The temperature units bit
lets you select temperature engineering units in °C or °F for RTD input types.
This bit field is only active for RTD input types. It is ignored when the
resistance input type is selected.
Table 4.21 Bit Descriptions for Temperature Units Selection
Binary
Value
0°Cdisplay the channel data word in °C.
1°Fdisplay the channel data word in °F.
SelectIf you want to
Filter Frequency Selection (Bits 9 and 10)
The following table shows the descriptions for bits 9 and 10. The channel filter
frequency bit field lets you select one of four filters available for a channel. The
filter frequency affects the channel update time and noise rejection
characteristics (refer to Chapter 3 for details).
Table 4.22 Bit Descriptions for Filter Frequency Selection
Binary
Value
0028 HzProvide both 50 Hz and 60 Hz AC line noise filtering. This setting
0150/60 HzProvide both 50 Hz and 60 Hz AC line noise filtering.
10800 HzProvide 800 Hz AC line noise filtering.
116400 HzProvide 6400 Hz AC noise filtering. This setting decreases the
SelectDescription
increases the channel update time, but also increases the noise
rejection.
noise rejection, but also decreases the channel update time.
Channel Enable Selection (Bit 11)
The next table shows the description for bit 11. You use the channel enable bit
to enable a channel. The RTD module only scans those channels that are
enabled. To optimize module operation and minimize throughput times, you
should disable unused channels by setting the channel enable bit to zero.
When set (1), the channel enable bit is used by the module to read the
configuration word information you have selected. While the enable bit is set,
modification of the configuration word may lengthen the module update time
for one cycle. If any change is made to the configuration word, the change
must be reflected in the status word before new data is valid. (Refer to Channel Status Checking on page 4-19.)
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4-18 Channel Configuration, Data, and Status
While the channel enable bit is cleared (0), the channel data word and status
word values are cleared. After the channel enable bit is set, the channel data
word and status word remain cleared until the RTD module sets the channel
status bit (bit 11) in the channel status word.
Table 4.23 Bit Descriptions for Channel Enable Selection
Binary Value SelectIf you want to
0channel disabledisable a channel. Disabling a channel causes the
channel data word and the channel status word to be
cleared.
1channel enableenable a channel.
Excitation Current Selection (Bit 12)
The following table shows the description for bit 12. Use this bit to select the
magnitude of the excitation current for each enabled channel. Choose from
either 1.0 mA or 0.25 mA. This bit field is active for all inputs. A lower current
reduces the error due to RTD self heating, but provides a lower signal-to-noise
ratio. Refer to RTD vendor for recommendations. See Appendix A for general
information.
Table 4.24 Bit Description for Excitation Current Selection
Binary
Value
01.0 mASet the excitation current to 1.0 mA.
10.25 mASet the excitation current to 0.25 mA.
SelectDescription
Calibration Disable (Bit 13)
The module can disable or enable periodic calibration by setting the
calibration disable bit for channel 0. Setting this bit to 0 enables the periodic
calibration, which occurs once every 5 minutes. Setting this bit to 1 disables
the periodic calibration
Lead Resistance Measurement Enable (Bits 14 and 15)
The module can disable lead resistance measurement, periodically measure the
lead resistance, or measure the lead resistance on each acquisition for each one
of the 8 channels. Setting a channel’s lead resistance enable bits to 00 disables
the lead resistance measurement. Setting a channel’s lead resistance enable bits
to 01 enables the periodic measurement of the lead resistance, which occurs
once every five minutes. Setting a channel’s lead resistance enable bits to 10
enables measurement of the lead resistance on each acquisition cycle.
Publication 1746-UM003A-EN-P
Channel Configuration, Data, and Status 4-19
Channel Data Word
The actual RTD or resistance input sensor values reside in I:e.0 through I:e.7
of the RTD module input image file. The data values present depend on the
input type and data format you have selected in your configuration for the
channel. When an input channel is disabled, its data word is reset (0).
Two conditions must be true for the value of the data word to be valid:
• The channel must be enabled (channel status bit = 1).
• There must be no channel errors or channel LED on (channel error bit = 0)
Figure 4.6 Module Input Image (Data Words)
I:e.0
I:e.1
I:e.2
I:e.3
I:e.4
I:e.5
I:e.6
Channel 0 Data Word
Channel 1 Data Word
Channel 2 Data Word
Channel 3 Data Word
Channel 4 Data Word
Channel 5 Data Word
Channel 6 Data Word
Channel Status Checking
I:e.7
Channel 7 Data Word
The channel status word is a part of the RTD module’s input image. Input
words 8 through 15 (Class 3 only) correspond to and contain the configuration
status of channels 0 through 7 respectively. You can use the data provided in
the status word to determine if the data word for any channel is valid per your
configuration in O:e.0 through O:e.7 or O:e.23 (Class 3 only).
For example, whenever a channel is disabled (O:e.x/11 = 0), its corresponding
status word shows all zeros. This condition tells you that input data contained
in the data word for that channel is not valid and should be ignored.
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4-20 Channel Configuration, Data, and Status
Figure 4.7 Module Input Image (Status Word)
I:e.8
I:e.9
I:e.10
I:e.11
I:e.12
I:e.13
I:e.14
I:e.15
Channel 0 Status Word
Channel 1 Status Word
Channel 2 Status Word
Channel 3 Status Word
Channel 4 Status Word
Channel 5 Status Word
Channel 6 Status Word
Channel 7 Status Word
The channel status word can be analyzed bit by bit. Each bit’s status (0 or 1)
tells you how the input data from the RTD sensor or resistance device
connected to a specific channel is translated for your application. The bit status
also informs you of any error condition and can tell you what type error
occurred.
A bit-by-bit examination of the status word is provided in the following table.
Publication 1746-UM003A-EN-P
Channel Configuration, Data, and Status 4-21
Table 4.25 Channel 0 through 7 Status Word (I:e.8 through I:e.15) - Bit Definitions
Engineering units x 10
10Scaled-for-PID
11Proportional Counts
6 through 7 Broken input
status
00Set to Zero
01Set to Upscale
10Set to Downscale
11Not used
8Temperature
units status
9 through 10 Filter frequency
status
0
1
Degrees C
Degrees F
0028 Hz
0150/60 Hz
(5)
(5)
10800 Hz
116400 Hz
11Channel enable
status
12Calibration Error
0Channel Disabled
1Channel Enabled
0OK
1Error
13Broken input
0OK
1Error
14Out-of-range
error status
15Configuration
Error
(1) Actual value at 0°C is 9.042Ω per SAMA standard RC21-4-1966.
(2) Actual value at 0°C is 100Ω per DIN standard.
(3) Values are in 0.1 degree /step or 0.1Ω/step for all resistance input types, except 150Ω. For the 150Ω resistance input type, the values are in 0.01Ω/step.
(4) Values are in 1 degree /step or 1Ω/step for all resistance input types, except 150Ω. For the 150 Ω resistance input type, the values are in 0.1Ω/step.
(5) This bit is cleared (0) when a resistance device, such as a potentiometer, is selected.
0OK
1Error
0
1
OK
Error
(1)
(2)
(3)
(4)
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4-22 Channel Configuration, Data, and Status
Explanations of the status conditions follow.
IMPORTANT
The status bits reflect the settings that were made in the
configuration word. However, two conditions must be true
if the status reflected is to be accurate:
• The channel must be enabled.
• The channel must have processed any new configuration
data.
Input Type Status (Bits 0 through 3)
The input type bit field indicates what type of input device you have
configured for the channel. This field reflects the input type selected in bits 0
through 3 of the channel configuration word when the channel is enabled. If
the channel is disabled, these bits are cleared (0).
Data Format Status (Bits 4 and 5)
The data format bit field indicates the data format you have defined for the
channel. This field reflects the data type selected in bits 4 and 5 of the channel
configuration word when the channel is enabled. If the channel is disabled,
these bits are cleared (0).
Publication 1746-UM003A-EN-P
Broken Input Status (Bits 6 and 7)
The broken input bit field indicates how you have defined the channel data to
respond to an open-circuit or short-circuit condition. This field reflects the
broken input type selected in bits 6 and 7 of the channel configuration word
when the channel is enabled. If the channel is disabled, these bits are cleared
(0).
Temperature Units Status (Bit 8)
The temperature units field indicates the state of the temperature units bit in
the configuration word (bit 8). This feature is only active for RTD input types
with the channel enabled. This bit is cleared (0) if the channel is disabled or if
the input type is a resistance device such as potentiometer.
Channel Configuration, Data, and Status 4-23
Channel Filter Frequency (Bits 9 and 10)
The channel filter frequency bit field reflects the filter frequency you selected
in bits 9 and 10 of the configuration word when the channel is enabled. This
feature is active for all input types. If the channel is disabled, these bits are
cleared (0).
Channel Enable Status (Bit 11)
The channel enable status bit indicates whether the channel is enabled or
disabled. This bit is set (1) when the channel enable bit is set in the
configuration word (bit 11) and there is valid data in the channel’s data word.
The channel status bit is cleared (0) if the channel is disabled.
Calibration Error (Bit 12)
If a calibration error occurs this flag is set. A calibration error is a fatal error. It
indicates that the module was not able to complete its on board calibration
process. A calibration error could effect individual channels, but may get set on
all channels at the same time if the ADC has a hardware fault.
Broken Input Error (Bit 13)
This bit is set (1) whenever an enabled channel detects a broken input
condition. A broken input error is declared for the following reasons:
• Open-circuit - excitation current is less than 50% of the selected current.
• Short-circuit - calculated lead wire compensated RTD resistance is less than 3
ohms.
The open-circuit error is active for all RTD and resistance inputs, while the
short-circuit error is valid only for RTD inputs. If a broken input is detected,
the module sends either zero, upscale, or downscale data to the channel data
word for that channel, depending on your channel configuration bits 6 and 7.
A broken input error takes precedence over an out-of-range error states. There
is not an out-of-range error when an open-circuit or short circuit is detected.
This bit is cleared if the channel is disabled or if the channel operation is
normal.
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4-24 Channel Configuration, Data, and Status
Out-Of-Range Error (Bit 14)
This bit is set (1) whenever a configured channel detects an over-range
condition for the input channel data, regardless of input type. This bit is also
set (1) whenever the module detects an under-range condition when the input
type is an RTD. An out-of-range error is declared for either of the following
conditions:
• Over-range - The RTD temperature is greater than the maximum allowed
(default or user-set) temperature or the resistance input type is greater than
the maximum allowed (default or user-set) resistance. When this occurs, the
channel data word is set to its maximum value.
• Under-range - The RTD temperature is less than the minimum allowed
(default or user-set) temperature. When this occurs, the channel data word
is set to its minimum value.
IMPORTANT
There is no under-range error for a direct resistance input
(default scaling).
This bit is cleared (0) for the following conditions:
• Channel is disabled.
• Channel operation is normal, the out-of-range condition clears
• Broken input error bit (bit 13) is set (1).
Configuration Error (Bit 15)
This bit is set (1) whenever an enabled and configured channel detects that the
channel configuration word is not valid. A configuration word is not valid for
any of the following reasons:
• Input type is a 10Ω Copper RTD and the excitation current is set for 0.25
mA, which is not allowed.
• Lead R Enable bits 14 and 15 are set to 11, which is invalid.
• Broken Input select bits 6 and 7 are set to 11, which is invalid.
• Data format bits are set to 11, and the lower limit user-set scale is equal to
the upper limit user-set scale and not equal to 0.
Publication 1746-UM003A-EN-P
All other status bits reflect the settings from the configuration word (even those
settings that may be in error). However, bit 15 is cleared if the channel is
disabled or if channel operation is normal.
Chapter
5
Ladder Programming Examples
Earlier chapters explained how the configuration word defines the way a
channel operates. This chapter shows the programming required to enter the
configuration word into the processor memory. It also provides you with
segments of ladder logic specific to unique situations that might apply to your
programming requirements. The example segments include:
• initial programming of the configuration word
• dynamic programming of the configuration word
• verifying channel configuration changes
• interfacing the RTD module to a PID instruction
• using proportional counts scaling (example)
• monitoring channel status bits
• invoking autocalibration
Device Configuration
Pilot Light O:2/1
Pilot Light O:2/0
Push-button Switch I:1/1
The following illustration is used for clarification of the ensuing ladder logic
examples and is not intended to represent an RTD application.
IMPORTANT
1746-NR8 RTD Module
1746-OB8 DC Output Module (Sourcing)
1746-IB8 DC Input Module (Sinking)
SLC Processor
Ch 0 Alarm Ch 1 Alarm Ch 2 Alarm Ch 3 Alarm
Autocalibration
F8
Chapter 7 shows a typical application for the RTD module.
RTD 0
RTD 1
RTD 2
RTD 3
Pilot Light O:2/3
Pilot Light O:2/2
Selector Switch I:1/0
1230
Display Panel
Slot #
˚
C
°
F
1Publication 1746-UM003A-EN-P
5-2 Ladder Programming Examples
Initial Programming
111 0
To enter data into the channel configuration word (O:e.0 through O:e.7)
when the channel is disabled (bit 11 = 0), follow the example below.
Refer to page 4-5 for specific configuration details.
Example - Configure eight channels of a RTD module residing in slot 3 of a
1746 chassis. Configure the first four channels with one set of parameters, and
the last four channels with a different set of parameters.
Figure 5.1 Configuration Word Setup for Channels 0 through 3
1112141513
10
9108
16700
1
45
0
1
000
Bit Number
0123
Bit Setting
0
Configures Channel For:
Ω Platinum RTD
100
Scaled-for-PID
Broken Input (Zero Data Word)
Degrees Fahrenheit (°F)
50/60 Hz Filter Frequency
Channel Enabled
0.25 mA Excitation Current
Calibration Enabled
Lead R Always
Figure 5.2 Configuration Word Setup for Channels 4 Through 7
1112141513
001 1
11
9108
0
06701
45
1
0
100
0123
0
Configures Channel For:
10
Ω Copper RTD (426)
Engineering Units x 10
Broken Input (Set Upscale)
Degrees Celsius (°C)
800 Hz Filter Frequency
Channel Enabled
0.25 mA Excitation Current
Calibration Disabled
Lead R Periodic
Publication 1746-UM003A-EN-P
Ladder Programming Examples 5-3
This example transfers configuration data and sets the channel enable bits of all
eight channels with a single file copy instruction. The file copy instruction
copies 8 data words from an integer file you create in the SLC’s memory, to the
RTD module’s channel configuration words. This procedure is described
below.
Figure 5.3 Copy File Data Flow
AddressAddress
NI0:0
NI0:1
NI0:2
NI0:3
NI0:4
NI0:5
NI0:6
NI0:7
Source Data FileDestination Data File
Channel Configuration Word 0
Channel Configuration Word 1
Channel Configuration Word 2
Channel Configuration Word 3
Channel Configuration Word 4
Channel Configuration Word 5
Channel Configuration Word 6
Channel Configuration Word 7
Channel Output Word 0
O:3.0
O:3.1
Channel Output Word 1
O:3.2
Channel Output Word 2
Channel Output Word 3
O:3.3
Channel Output Word 4
O:3.4
O:3.5
Channel Output Word 5
O:3.6
Channel Output Word 6
Channel Output Word 7
O:3.7
Procedure
1.
1. Using the memory map function to create a data file, create integer file
1.1.
N10. Integer file N10 should contain eight elements (N10:0 through
N10:7).
2.
2. Using the RSLogix 500 data monitor function, enter the configuration
2.2.
parameters for all eight RTD channels into a source integer data file N10.
Refer to the Configuration Word Setup illustration for the bit values. See
Appendix B for a channel configuration worksheet.
3. Use the copy file instruction (COP) to copy the contents of integer file
3.3.
N10 to the eight consecutive output words of the RTD module beginning
with O:3.0. To do this, program a rung as shown below. All elements are
copied from the specified source file to the destination during the first scan
following power up.
Publication 1746-UM003A-EN-P
5-4 Ladder Programming Examples
On power up, bit S:1/15 is set for the first
program scan and integer file N10 is sent to
the RTD module channel configuration word.
Dynamic Programming
Rung 2:0
Rung 2:1
Initialize RTD moduleFirst Pass Bit
S:1
] [
15
COP
COPY FILE
Source#N10:0
Dest#O:3.0
Length8
The ladder below explains how to change data in the channel configuration
word when the channel is currently enabled.
Example - Execute a dynamic configuration change to channel 2 of the RTD
module located in slot 3 of a 1746 chassis. Change from monitoring the
temperature in °F to monitoring in °C.
Figure 5.4 Program to Change Configuration Word Data
Set up all eight channels.
S:1
] [
15
Set channel 2 to display in °C (off) or °F (on).
I:1.0
] [
0
O:3.2
( )
8
COP
COPY FILE
Source#N10:0
Dest#O:3.0
Length8
Verifying Channel
Configuration Changes
Rung 2:2
END
When executing a dynamic channel configuration change, there is always a
delay from the time the ladder program makes the change to the time the RTD
module gives you a data word using that new configuration information.
Therefore, it is very important to verify that a dynamic channel configuration
change took effect in the RTD module, particularly if the channel being
dynamically configured is used for control.
Example - Execute a dynamic configuration change to channel 2 of the RTD
module located in slot 3 of a 1746 chassis and set an internal “data valid” bit
when the new configuration has taken effect.
Publication 1746-UM003A-EN-P
Figure 5.5 Program to Verify Configuration Word Data Changes
Set up all eight NR8 configuration registers. Registers N10:0 through N10:7 must
be loaded with the appropriate configuration words prior to execution.
First Pass
S:1
0000
15
Ladder Programming Examples 5-5
COP
Copy File
Source
Dest
Length
#N10:0
#O:3.0
8
I:1.0
0001
0
This rung is used to verify the configuration word after a dynamic
change. Alarm bits can also be programmed in this rung to check for
status errors.
0002
EQU
Equal
Source A
Source B
0003
Interfacing to the PID
Instruction
O:3.2
8
I:3.10
0<
O:3.2
0<
The RTD module was designed to interface directly to the SLC 5/02,
SLC 5/03, SLC 5/04 and SLC 5/05 PID instruction without the need for an
intermediate scale operation. Use RTD channel data as the process variable in
the PID instruction.
B3:0
2
END
To program this application, proceed as follows:
1.
1. Select 100
1.1.
Ω Platinum RTD, α= 0.003916, as the input type by setting bit
0 = 0, bit 1 = 0, bit 2 = 1 and bit 3 = 0 in the configuration word.
2.
2. Select scaled-for-PID as the data type by setting bit 4 = 0 and bit 5 = 1 in
2.2.
the configuration word.
Publication 1746-UM003A-EN-P
5-6 Ladder Programming Examples
0000
0001
ATTENTION
!!!!
When using the module’s scaled-for-PID data format with
the SLC PID function, ensure that the PID instruction
parameters Maximum Scaled S
Scaled S
(word 8) match the module’s minimum and
min
(word 7) and Minimum
max
maximum scaled range, in engineering units, (e.g. -200°C
to +850°C) for each channel. This allows you to accurately
enter the setpoint in engineering units (°C, °F).
Figure 5.6 Programming for PID Application
Use register N10:0 as configuration word for channel 0.
First Pass
S:1
15
Entering Address N11:0 allocates elements N11:0 to N11:22 for required Control Block file length of 23 words. The Process
Variable is address I:3.0, which stores the value of input data word 0 (channel 0). Output of the PID instruction is stored at
address N11:23 (Control Variable Address).
I:3.8
11
PID
PID
Control Block
Process Variable
Control Variable
Control Block Length
Setup Screen
Move
Source
Dest
MOV
N10:0
0<
O:3.0
0<
N11:0
I:3.0
N11:23
23
0002
Publication 1746-UM003A-EN-P
END
Ladder Programming Examples 5-7
Using the Proportional
Counts Data Format
with the User-set Scaling
(Class 3)
Ten elements are copied from the specified source
address (N10:0) to the specified output (O:3.0). Each
element is a 16-bit integer as shown in the data table
at the bottom of the page.
The RTD module can be set up to return data to the user program that is
specific to the application. Assume that the user controls the line speed of a
conveyor using a 1000
Ω potentiometer connected to channel 0 of the RTD
module. The line speed will vary between 3 feet/minute when the
potentiometer is at 0
1000
Ω.
Ω and 50 feet/minute when the potentiometer is at
Example - Configure the RTD module in Class 3 operation to return a value
between 3 and 50 in the data word for channel 0. Proceed as follows:
1.
1. Set bits 0 through 3 of configuration word 0 to 1110 to select the
1.1.
1000
Ω potentiometer input type.
2.
2. Set bits 4 and 5 of configuration word 0 to 11 to select proportional counts
2.2.
data format.
3.
3. Enter 3 as the low range into N10:8.
3.3.
4.
4. Enter 50 as the high range into N10:9.
4.4.
Figure 5.7 Programming for PID Applications)
Rung 2:0
First Pass BitInitialize RTD module.
S:1
] [
15
COP
COPY FILE
Source#N10:0
Dest#O:3.0
Length10
Rung 2:1
The
Source
of this instruction is the data word from the
RTD module, which is a number between 3 and 50. The
Dest
in this application is an analog output channel
controlling the speed of the conveyor motor drive. The
Rate and Offset parameters should be set per your
application. Refer to the S
Instruction Set Reference Manual
1747-6.15) or the
1746-6.4) for specific examples of the SLC instruction.
LC 500 and MicroLogix 1000
(publication
Analog I/O User Manual
(publication
Rung 2:2
For Class 3 operation registers N10:8 and N10:9 can be used to scale channel 0
for a minimum conveyor speed of 3 ft./minute and a maximum conveyor
speed of 50 ft./minute
I:3.8
] [
11
SCL
SCALE
SourceI:3.0
Rate [/10000]
Offset
Dest
END
Publication 1746-UM003A-EN-P
5-8 Ladder Programming Examples
Table 5.1 Data Table (Class 3)
Address 1514131211109876543210
N10:00010100000111110
N10:10000000000000000
N10:20000000000000000
N10:30000000000000000
N10:40000000000000000
N10:50000000000000000
N10:60000000000000000
N10:70000000000000000
N10:80000000000000011
N10:90000000000110010
Monitoring Channel Status
Bits
The following illustration shows how to monitor the open- and short-circuit
error bits of each channel and set an alarm in the processor if one of the RTDs
or resistance-input devices (such as a potentiometer) opens or shorts. An
open-circuit error can occur if the RTD or resistance-input device breaks or
one of the RTD or resistance-input device wires get cut or disconnected from
the terminal block. A short-circuit condition applies only to RTD input.
Publication 1746-UM003A-EN-P
0000
First Pass
S:1
15
Figure 5.8 Programming to Monitor Channel Status
Ladder Programming Examples 5-9
COP
Copy File
Source
Dest
Length
#N10:0
#O:3.0
8
0001
0002
Channel 0
Enable
I:3.8
11
Channel 1
Enable
I:3.9
11
Channel 0
Broken Input
I:3.8
13
Channel 0
Out of Range
I:3.8
14
Channel 0
Configuration
Error
I:3.8
15
Channel 1
Broken Input
I:3.9
13
Channel 1
Out of Range
I:3.9
Channel 0
Alarm
O:2
0
1746-O*16
Channel 1
Alarm
O:2
1
1746-O*16
14
Channel 1
Configuration
Error
I:3.9
15
Publication 1746-UM003A-EN-P
5-10 Ladder Programming Examples
Channel 7
Enable
0003
0004
Invoking Autocalibration
Channel 7
I:3.15
11
Broken Input
I:3.15
13
Channel 7
Out of Range
I:3.15
14
Channel 7
Calibration
Error
I:3.15
15
Autocalibration occurs whenever:
Channel 7
Alarm
O:2
7
1746-O*16
END
• power is provided to the module
• a change is made to its input type, filter frequency, or excitation current
• an operating channel is disabled and re-enabled using its enable bit
• the periodic calibration bit is toggled from 1 (disable) to 0 (enable) and back
to 1 (disable)
Referring to the following ladder, you can command your module to perform
an autocalibration cycle by toggling the periodic calibration bit (bit 15).
To maintain system accuracy we recommend that you periodically perform an
autocalibration cycle, for example:
• whenever an event occurs that greatly changes the internal temperature of
the control cabinet, such as opening or closing its door
• at a convenient time when the system is not making product, such as during
a shift change.
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Ladder Programming Examples 5-11
ATTENTION
Several channel cycles are required to perform an
autocalibration and it is important to remember that
during autocalibration the module is not converting input
data.
!!!!
Example
Example - Command the RTD module to perform an autocalibration of
ExampleExample
channel 0. The RTD module is in slot 3. This example assumes that the
periodic calibration bit (bit 15) is in the disabled state (set to 1).
Programming to Invoke Autocalibration
Rung 2:0
Rung 2:1
Channel 0 Flag
B3
] [
1
Condition for
Autocalibration
I:1
] [
1
B3
[OSR]
O:3.0
(L)
15
Channel 0 Flag
B3
(U)
1
O:3.0
(U)
0
15
Channel 0 Flag
B3
(L)
1
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5-12 Ladder Programming Examples
Publication 1746-UM003A-EN-P
Chapter
6
Module Diagnostics and Troubleshooting
This chapter describes troubleshooting using the channel status LEDs as well
as the module status LED. A troubleshooting flowchart is shown on page 6-6.
It explains the types of conditions that might cause an error to be reported and
gives suggestions on how to resolve the problem. Major topics include:
• module operation vs. channel operation
• power-up diagnostics
• channel diagnostics
• LED indicators
• troubleshooting flowchart
• replacement parts
• contacting Allen-Bradley
Module Operation vs.
Channel Operation
The RTD module performs operations at two levels:
• module-level operations
• channel-level operations
Module-level operations include functions such as power-up configuration and
communication with the SLC processor.
Channel-level operations describe channel-related functions, such as data
conversion and open-circuit or short-circuit (RTDs only) detection.
Internal diagnostics are performed at both levels of operation and any error
conditions detected are immediately indicated by the module’s LEDs and
status to the SLC processor.
1Publication 1746-UM003A-EN-P
6-2 Module Diagnostics and Troubleshooting
Power-Up Diagnostics
Channel Diagnostics
At module power-up, a series of internal diagnostic self-tests is performed. The
module status LED remains off during power-up. The channel LEDs are
turned on until the self test has finished. If any diagnostic test fails, the module
enters the module error state. If all tests pass, the module status LED is turned
on and the channel status LED is turned on for the respective enabled channel.
The module continuously scans all enabled channels and communicates with
the SLC processor. During power- up, the RTD module does not
communicate with the processor.
When a channel is enabled (bit 11 = 1), a diagnostic check is performed to see
that the channel has been properly configured. In addition, the channel is
tested for out-of-range, open-circuit, and short-circuit faults on every scan.
A failure of any channel diagnostic test causes the faulted channel status LED
to blink. All channel faults are indicated in bits 13 through 15 of the channel’s
status word. Channel faults are self-clearing (bits 13 and 14 of status word). Bit
15 is not cleared until the correct change is made to the channel configuration.
The channel LED stops blinking and resumes steady illumination when the
fault conditions are corrected.
LED Indicators
IMPORTANT
If you clear (0) a channel enable bit (11), all channel status
information (including error information) is reset (0).
The RTD module has nine LEDs. Eight of these are channel status LEDs
numbered to correspond to each of the RTD/resistance input channels and
one is a module status LED.
Figure 6.1 LED Display
INPUT
CHANNELSTATUS
MODULE
RTD/resistance
04123
567
Channel LEDs
Publication 1746-UM003A-EN-P
Module Diagnostics and Troubleshooting 6-3
The following tables explain the function of the channel status LEDs while the
module status LED is turned on.
Table 6.1 Module Status Description
If Module
Status LED is:
ONProper OperationNo action required.
Off or FlashingModule Fault Cycle power. If condition persists,
Table 6.2 Channel Status Description
Indicated Condition:Corrective Action:
replace the module or call your
local distributor or Rockwell
Automation for assistance.
Error Codes
LED
Power-up
Ch 0-7 StatusOnOn/Off
(1)
Module Operation
(No Error)
(2)
Module ErrorChannel
Error
Off
(3)
Flashes
Mod. StatusOffOnFlashes/OffOn
(1) Module is disabled during powerup.
(2) Channel status LED is On if the respective channel is enabled and Off if the channel is disabled.
(3) Error if channel is enabled.
I/O error codes are reported in word S:6 of the SLC processor status file. The
format for the error codes in the status word (S:6) is shown in the illustration
below. The characters denoted as XX in the illustration below represent the slot
number (Hex) for the module. The characters denoted as YY represent the
2-digit hex code for the fault condition.
The error codes applicable to the RTD Module range from 50H to 5AH.
Some of these are non-recoverable errors. For a description of the error codes,
refer to SLC 500 and MicroLogix 1000 Instruction Set Reference Manual,
publication 1747-6.15.
XXYY
XX - Chassis Slot Number (Hex)
YY - Error Code (Hex)
Publication 1746-UM003A-EN-P
6-4 Module Diagnostics and Troubleshooting
Channel Status LEDs (Green)
The channel LED is used to indicate channel status and related error
information contained in the channel status word. This includes conditions
such as:
• normal operation
• channel-related configuration errors
• broken input circuit errors such as open- or short-circuit (RTDs only)
• out-of-range errors
All channel errors are recoverable errors and after corrective action, normal
operation resumes.
Invalid Channel Configuration
Whenever a channel’s configuration word is improperly defined, the channel
LED blinks and bit 15 of the channel status word is set. Configuration errors
occur for the following invalid combinations:
• Input type is a 10Ω Copper RTD and the excitation current is set for 0.25
mA, which is not allowed.
• Lead R Enable bits 14 and 15 are set to 11, which is invalid.
• Broken Input select bits 6 and 7 are set to 11, which is invalid.
• Data format bits are set to 11, and the lower limit user-set scale is equal to
the upper limit user-set scale and not equal to 0.
Open- and Short-Circuit Detection
An open- or short-circuit test is performed on all enabled channels on each
scan. Whenever an open-circuit or short-circuit condition occurs (see possible
causes listed below), the channel LED blinks and bit 13 of the channel status
word is set.
Possible causes of an open or short circuit include:
• The RTD or potentiometer may be broken.
• An RTD or potentiometer wire may be loose or cut.
• The RTD or potentiometer may not have been installed on the configured
channel.
• The RTD may be internally shorted.
• The RTD may be installed incorrectly.
• Wrong RTD used for type/configuration selected.
Publication 1746-UM003A-EN-P
Module Diagnostics and Troubleshooting 6-5
If an open- or short-circuit is detected, the channel data word reflects input
data as defined by the broken input configuration bits (6 and 7) in the channel
configuration word.
Out-Of-Range Detection
Whenever the data received at the channel data word is out of the defined
operating range, an over-range or under-range error is indicated and bit 14 of
the channel status word is set.
IMPORTANT
There is no under-range error for a direct resistance input
(default scaling).
For a review of the temperature range or resistance range limitations for your
input device, refer to the temperature ranges provided in Chapter 5 or the
user-specified range in configuration words 8 through 23 if proportional
counts is used.
Possible causes of an out-of-range condition include:
• The temperature is too hot or too cold for the RTD being used.
• Wrong RTD used for type/configuration selected.
• Bad potentiometer or RTD.
• Signal input from either potentiometer or RTD is beyond the user-set
scaling range.
Module Status LED (Green)
The module status LED is used to indicate module-related diagnostic or
operating errors. These non-recoverable errors may be detected at power-up or
during module operation. Once in a module error state, the RTD module no
longer communicates with the SLC processor. Channels are disabled and data
words are cleared (0).
Failure of any diagnostic test places the module in a non-recoverable state. To
exit this state, cycle power. If the power cycle does not work, then call your
local distributor or Rockwell Automation for assistance.
Publication 1746-UM003A-EN-P
6-6 Module Diagnostics and Troubleshooting
Figure 6.2 Troubleshooting Flowchart
Check LEDs
on module.
Module Status
LED is off.
Module fault
condition
Check to see
that module is
seated properly
in chassis.
Cycle power.
Module Status
LED is on.
Normal module
operation
End
Channel Status
LED(s) is
flashing.
Fault
condition
Check channel
status word
bits 13 to 15
Bit 15
set (1)
Channel Status
LED is off.
Channel is not
Enable channel if
desired by setting
channel config.
word (bit 11=1).
Configuration error.
Check and correct the
configuration word for
this channel.
enabled.
Retry.
Channel Status
LED is on.
Channel is
enabled and
working properly.
End
Is problem
corrected?
Contact your
local distributor
or Rockwell
Automation.
Publication 1746-UM003A-EN-P
Yes
No
End
Bit 14
set (1)
Bit 13
set (1)
Out-of-range error
indicating that either an
over-range or under-range
condition exists. For all
over-range, the input signal
is greater than the high
scale limit for the channel.
For under-range, the input
signal is less than the low
scale limit for the channel.
A broken input error or
short-circuit (RTD)
condition is present. Check
channel for open or loose
connections (RTD and
potentiometer inputs) and
check channel for
short-circuit condition (RTD
only). Retry.
Yes
Is problem
corrected?
No
Contact your
local distributor
or Rockwell
Automation.
Module Diagnostics and Troubleshooting 6-7
Replacement Parts
Contacting Rockwell
Automation
The RTD module has the following replaceable parts:
Table 6.3 Parts List
PartPart Number
Replacement Terminal Block1746-RT35
Replacement Terminal Cover1746-R13 Series C
1746-NR8 User Manual1746-UM003A-EN-P
If you need to contact Rockwell Automation for assistance, please have the
following information available when you call:
• a clear statement of the problem including a description of what the system
is actually doing. Note and record the LED states; also, note input and
output image words for the RTD module.
• a list of things you have already tried to remedy the problem
• processor type, 1746-NR8 series letter, and firmware (FRN) number. See
label on left side of processor.
• hardware types in the system including I/O modules and chassis
• fault code if the SLC processor is faulted
Publication 1746-UM003A-EN-P
6-8 Module Diagnostics and Troubleshooting
Publication 1746-UM003A-EN-P
Chapter
7
Application Examples
This chapter provides two application examples to help you use the RTD input
module. They are defined as a:
• basic example
• supplementary example
The basic example builds on the configuration word programming provided in
Chapter 5 to set up one channel for operation. The module operates in Class 1
mode for this sample. This setup is then used in a typical application to display
temperature.
The supplementary example demonstrates how to perform a dynamic
configuration of all eight channels. The example sets up an application that
allows you to manually select whether the displayed RTD input data for any
channel is expressed in °C or °F. The module operates in Class 3 operation in
order to support the scaling and status.
Basic Example
SLC 5/04
The following illustration indicates the temperature of a bath on an LED
display. The display requires binary coded decimal (BCD) data, so the program
must convert the temperature reading from the RTD module to BCD before
sending it to the display. This application displays the temperature in °F.
Figure 7.1 Device Configuration
1746-OB16
1746-NR8
LED Display
(DC Sinking Inputs, BCD Format)
Ω Platinum RTD
200
Bath
Channel Configuration
Configure the RTD channel with the following setup:
• 200Ω Platinum RTD
• °F in whole degrees
• zero data word in the event of an open or short circuit
• 28 Hz input filter
• 1.0 mA excitation current
1Publication 1746-UM003A-EN-P
7-2 Application Examples
Table 7.1 Channel Configuration Worksheet
(With Settings Established for Channel 0)
10 = scaled-for-PID (0 to 16383)
11 = proportional counts (-32768 to
+32767)
Bits 6 and 7Broken Input Select00 = zero01 = upscale10 = downscale11 = lnvalid
Bit 8Temperature Units
0 = degrees Celsius1 = degrees Fahrenheit
Select
Bits 9 and 10Filter Frequency Select 00 = 28 Hz01 = 50/60 Hz10 = 800 Hz11 = 6400 Hz
Bit 11Channel Enable0 = channel disabled1 = channel enabled
Bit 12Excitation Current Select 0 = 1.0 mA1 = 0.25 mA
Bit 13Cal. Disable0 = enable1 = disable
Bits 14 and 15Lead R. Disable00 = disable01 = periodic10 = always
(1) Actual value at °C is 9.042Ω per SAMA standard RC21-4-1966.
(2) Actual value at 0°C is 100Ω per DIN standard.
(3) Values are in 0.1° /step or 0.1 Ω/step for all resistance input types, except 150Ω. For the 150Ω resistance input type, the values are in 0.01Ω/step.
(4) Values are in 1° /step or 1Ω /step for all resistance input types, except 150Ω. For the 150Ω resistance input type, the values are in 0.1Ω/step.
Program Listing
Since a 7-segment LED display is used to display temperature, the temperature
data must be converted to BCD. The 16-bit data word representing the
temperature value is converted into BCD values by the program shown in the
following illustration.
Publication 1746-UM003A-EN-P
Figure 7.2 Program to Convert F to BCD
Rung 2.0
Rung 2.1
First Pass Bit
S:1
] [
15
Convert the channel 0 data word (degrees F) to BCD values and write this to the LED display. If
channel 0 is ever disabled, a zero is written to the display.
Application Examples 7-3
Initialize Channel 0 of
RTD Module.
MOV
MOVE
SourceN10:0
DestO:3.0
TOD
TO BCD
SourceI:3.0
DestN7:0
(1)
MVM
MASKED MOVE
SourceN7:0
Mask0FFF
DestO:2.0
address 15 data 0 address 15 data 0
N10:0 0000 1001 0001 0001
Supplementary Example
(1) The use of the masked move instruction with the OFFF mask allows you to use outputs 12, 13, 14, and 15
for other output devices in your system. The 7-segment display uses outputs 0 through 11.
Rung 2.2
END
Table 7.2 Data Table
Application Setup (Eight Channels °C or °F)
The following illustration shows how to display the temperature of several
different RTDs at one annunciator panel. A selector switch (I:2/0) allows the
operator to choose between displaying data in °C and °F. Each of the displays is
a 4-digit, 7-segment LED display with the last digit representing tenths of a
degree. The displays have dc-sinking inputs and use a BCD data format.
Publication 1746-UM003A-EN-P
7-4 Application Examples
Figure 7.3 Device Configuration for Displaying Many RTD Inputs
SLC 5/04
1746-NR8
Display Panel
1746-IB8
Ambient
.
(8) 1746-OB16
.
Bath
.
°
C
°
F
..
Chilled H2OSteam
..
200
Ambient Temperature
604
Ω Nickel/Iron (518)
Bath
Ω Platinum
RTD (385)
Chilled H
O Pipe In
2
200Ω Platinum RTD (385)
Chilled H
1000
O Pipe Out
2
Ω Platinum RTD (385)
Steamed Pipe Out
Steamed Pipe In
Ambient Temperature
604
Ω Nickel/Iron (518)
Chilled H
Chilled H
O Pipe In
2
Ω Platinum RTD (385)
200
O Pipe Out
2
Selector Switch (I:2/0)
Bath
200
Ω Platinum RTD (385)
Ω Platinum RTD (385)
1000
Steamed Pipe Out
Steamed Pipe In
Channel Configuration
(see completed worksheet on page 7-5)
Configuration setup for ambient RTD:
• channels 0 and 4
• 604Ω Nickel/Iron (518)
• display temperature to tenths of a degree Celsius or Fahrenheit
• zero data word in the event of an open- or short-circuit
• 28 Hz input filter to provide 60 Hz line noise rejection
• use 1.0 mA excitation current for RTD
• scaling for -20°C to +60°C
Publication 1746-UM003A-EN-P
Application Examples 7-5
Configuration setup for bath RTD:
• channels 1 and 5
• 200Ω Platinum RTD (385)
• display temperature to tenths of a degree Celsius or Fahrenheit
• zero data word in the event of an open- or short-circuit
• 28 Hz input filter to provide 60 Hz line noise rejection
• use 1.0 mA excitation current for RTD
• scaling for 0°C to +60°C
• define upper and lower temperature limits
Configuration setup for steam RTD:
• channels 2 and 6
• 1000Ω Platinum RTD (385)
• display temperature to tenths of a degree Celsius or Fahrenheit
• zero data word in the event of an open- or short-circuit
• 50/60 Hz input filter to provide 60 Hz line noise rejection
• use 0.25 mA excitation current for RTD
• scaling for -20°C to +200°C
Configuration setup for chilled H
O RTD:
2
• channels 3 and 7
• 200Ω Platinum RTD (385)
• display temperature to tenths of a degree Celsius or Fahrenheit
• zero data word in the event of an open- or short-circuit
• 28 Hz input filter to provide 60 Hz line noise rejection
01 = engineering units, x10
Bits 6 and 7Broken Input Select00 = zero01 = upscale10 = downscale11 = Invalid
Bit 8Temperature Units
0 = degrees Celsius1 = degrees Fahrenheit
Select
Bits 9 and 10Filter Frequency Select 00 = 10 Hz01 = 50 Hz10 = 60 Hz11 = 250 Hz
Bit 11Channel Enable0 = channel disabled1 = channel enabled
Bit 12Excitation Current
0 = 1.0 mA1 = 0.25 mA
Select
Bit 13Calibration Enable0 = enable1 = disabled
Bits 14 and 15Lead Res. Enable00 = always01 = periodic10 = disable
(1) Actual value at 0 °C is 9.042Ω per SAMA standard RC21-4-1966.
(2) Actual value at 0 °C is 100Ω per DIN standard.
(3) Values are in 0.1°/step or 0.1Ω/step for all resistance input types, except 150Ω. For the 150Ω resistance input type, the values are in 0.01Ω/step.
(4) Values are in 1°/step or 1 Ω/step for all resistance input types, except 150Ω. For the 150Ω resistance input type, the values are in 0.1 Ω/step.
0110 = 500
0111 = 1000
1000 = 10
Ω Pt. (3916)
Ω Pt. (3916)
Ω Cu (427)
1001 = 120Ω Ni (618)
1010 = 120Ω Ni (617)
1011 = 604
(3)
(4)
Ω Ni-Fe (518)
1100 = 150Ω Potentiometer
(1)
(2)
1101= 500
1110= 1000
1111= 3000
Ω Potentiometer
Ω Potentiometer
Ω Potentiometer
10 = scaled-for-PID (0 to 16383)
11 = proportional counts (-32768 to +32767)
Publication 1746-UM003A-EN-P
7-6 Application Examples
Program Setup and Operation Summary
1.
1. The alarms section of the ladder program monitors for any out of range
1.1.
condition.
2.
2. Set up two configuration words in memory for each channel, one for °C
2.2.
and the other for °F. The following table shows the configuration word
allocation summary.
3. When the position of the degrees selector switch changes, write the
3.3.
appropriate channel configuration to the RTD module. Note that the use
of the OSR instruction (one-shot rising) makes these configuration changes
edge-triggered, that is, the RTD is reconfigured only when the selector
switch changes position.
4.
4. Convert the individual RTD data words to BCD and send the data to the
4.4.
respective LED displays.
Program Listing
The first two rungs of this program send the correct channel setup information
to the RTD module based on the position of the degrees selector switch.
Publication 1746-UM003A-EN-P
Figure 7.4 Program to Display Data On LEDs
If the degrees selector switch is turned to the Fahrenheit position, set up all eight
channels to read in degrees Fahrenheit.
Degrees Selector
Switch - Fahrenheit
Rung 2.0
Rung 2.1
I:2.0
] [
0
If the degrees selector switch is turned to the Celsius position, set up all four channels
to read in degrees Celsius.