Rockwell Automation 1790P-4R0 User Manual

CompactBlock LDX RTD/Resistance Input Module

1790D-4R0, 1790D-T4R0, 1790P-T4R0

User Manual

Important User Information

Because of the variety of uses for the products described in this publication, those responsible for the application and use of these products 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. In no event will Allen-Bradley be responsible or liable for indirect or consequential damage resulting from the use or application of these products.

Any illustrations, charts, sample programs, and layout examples shown in this publication 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 publication, notes may be used to make you aware of safety considerations. The following annotations and their accompanying statements help you to identify a potential hazard, avoid a potential hazard, and recognize the consequences of a potential hazard:

WARNING

Identifies information about practices or circumstances that can cause an explosion in a hazardous environment, which may lead to personal injury or death, property damage, or economic loss.

ATTENTION

Identifies information about practices or circumstances that can lead to personal injury or death, property damage, or economic loss.

RSNetWorx, RSNetWorx for DeviceNet, RSLogix 500, and RSLogix 5000 are trademarks of Rockwell Automation.

Belden is a trademark of Belden, Inc.

IMPORTANT

Identifies information that is critical for successful application and understanding of the product.

Rockwell Automation Support

Before you contact Rockwell Automation for technical assistance, we suggest you please review the troubleshooting information contained in this publication first.

If the problem persists, call your local Rockwell Automation representative or contact Rockwell Automation in one of the following ways:

Phone United

States/Canada

Outside United States/Canada

Internet 1. Go to http://www.ab.com

1.440.646.5800

You can access the phone number for your country via the Internet:

1. Go to http://www.ab.com

2. Click on Product Support (http://support.automation.rockwell.com)

3. Under Support Centers, click on Contact

Information

2. Click on Product Support (http://support.automation.rockwell.com)

Your Questions or Comments on this Manual

If you find a problem with this manual, please notify us by using the enclosed How Are We Doing form.

Overview

Installation and Wiring

Module Data, Status, and Channel Configuration for DeviceNet

Chapter 1

General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1

Hardware Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3

System Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4

Chapter Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-6

Chapter 2

Before You Begin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

Power Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

General Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2

Mounting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-6

Field Wiring Connections . . . . . . . . . . . . . . . . . . . . . . . . . 2-11

Chapter Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-18

Chapter 3

Module Memory Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

Accessing Input Image File Data . . . . . . . . . . . . . . . . . . . . 3-1

Input Data File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2

Data Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3

Filter Frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4

Channel Step Response . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5

Channel Cutoff Frequency . . . . . . . . . . . . . . . . . . . . . . . . . 3-6

Effective Resolution. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-8

Determining Module Update Time. . . . . . . . . . . . . . . . . . . 3-9

DeviceNet RTD/Resistance Module (1790D-4R0/T4R0) . . . . 3-9

Configure DeviceNet RTD/Resistance Modules

Using RSNetWorx . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-10

Chapter Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-14

Chapter 4

Diagnostics and Troubleshooting

Safety Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1

Module Operation vs. Channel Operation . . . . . . . . . . . . . 4-2

Power-up Diagnostics . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3

Channel Diagnostics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-4

Channel LED Indicator Operation . . . . . . . . . . . . . . . . . . . 4-5

Contacting Rockwell Automation . . . . . . . . . . . . . . . . . . . . 4-6

Chapter Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-6

Appendix A

Specifications

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Environmental Specifications . . . . . . . . . . . . . . . . . . . . . . . A-1

DeviceNet Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . A-2

PROFIBUS DP Specifications . . . . . . . . . . . . . . . . . . . . . . . A-2

General Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-3

RTD/Resistance Specifications . . . . . . . . . . . . . . . . . . . . . . A-4

Table of Contents ii

Two’s Complement Binary Numbers

Module Configuration for PROFIBUS

Appendix B

Positive Decimal Values . . . . . . . . . . . . . . . . . . . . . . . . . . B-1

Negative Decimal Values. . . . . . . . . . . . . . . . . . . . . . . . . . B-2

Appendix C

Configure PROFIBUS RTD/Resistance Modules

(1790P-T4R0) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-1

Configure RTD/Resistance Modules Using the SST PROFIBUS

Configuration Tool . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-1

Save the Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . C-6

Download the Configuration . . . . . . . . . . . . . . . . . . . . . . . C-7

Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-9

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Chapter

Overview

This chapter describes the four-channel 1790D-4R0/T4R0 RTD/resistance Input module and explains how the controller reads resistance temperature detector (RTD) or direct resistance-initiated analog input data from the module. Included is:

• a general description of hardware features

• an overview of module and system operation

• compatibility

General Description

The 1790D-4R0/T4R0 (1790P-T4R0) module supports RTD and direct resistance signal measurement applications that require up to four channels. The module digitally converts analog data and then stores the converted data in its image table.

The module supports connections from any combination of up to four input devices. Each channel is individually configurable via software for 2or 3-wire RTD or direct resistance input devices. Channels are compatible with 4-wire sensors, but the fourth sense wire is not used. When configured for RTD inputs, the module can convert the RTD readings into linearized digital temperature readings in °C or °F. When configured for resistance analog inputs, the module can convert voltages into linearized resistance values in ohms. The module assumes that the direct resistance input signal is linear prior to input to the module.

Each channel provides open-circuit (all wires) and over- and under-range detection and indication.

IMPORTANT

The module accepts input from RTDs with up to 3 wires. If your application requires a 4-wire RTD, one of the two lead compensation wires is not used, and the RTD is treated like a 3-wire sensor. The third wire provides lead wire compensation. See Chapter 2, Installation and Wiring, for more information.

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1-2 Overview

The module supports the following filter frequencies:

• 10 Hz

• 25 Hz

• 50 Hz

• 60 Hz

• 100 Hz

• 250 Hz

• 500 Hz

The module uses five input words for data and status bits. Module configuration is stored in the module memory. Configuration for 1790D-(T)4R0 is done via RSNetWorx for DeviceNet™ programming software. See Chapter 3, Module Data, Status, and Channel Configuration, for details on module configuration. Configuration for 1790P-T4R0 is done via PROFIBUS configuration software. See Appendix C for details.

RTD Compatibility

An RTD consists of a temperature-sensing element connected by two, three, or four wires that provide input to the module. The following table lists the RTD types that you can use with the module, including their temperature range, effective resolution, and accuracy.

Table 1.1 RTD Specifications

RTD Type Temperature

Range

100ohm Pt/α=0.00385 -200 to +850°C -2000 to +8500 0.1°C ±2.1°C 200ohm Pt/α=0.00385 -200 to +850°C -2000 to +8500 0.1°C ±2.1°C 500ohm Pt/α=0.00385 -200 to +650°C -2000 to +6500 0.1°C ±1.7°C 100ohm Pt/α=0.003916 -200 to +640°C -2000 to +6400 0.1°C ±1.68°C 200ohm Pt/α=0.003916 -200 to +640°C -2000 to +6400 0.1°C ±1.68°C 500ohm Pt/α=0.003916 -200 to +640°C -2000 to +6400 0.1°C ±1.68°C

100ohm Nickel -60 to 250°C -600 to 2500°C 0.1 °C ±0.62°C

120ohm Nickel -80 to 260°C -800 to 2600 0.1°C ±0.68°C

Scaling (Counts)

Resolution* Accuracy**

(0 to 55°C)

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200ohm Nickel -60C to 250°C -600 to 2500 0.1°C ±1.62°C

500ohm Nickel -60 to 250°C -600 to 2500 0.1°C ±0.62°C

*Filter set for 10 Hz

**Module only

Overview 1-3

Resister Device Compatibility

The following table lists the specifications for the resistance devices that you can use with the module.

Table 1.2 Resistance Device Specifications

Hardware Features

Resistance Type Range Scaling

Resolution* Accuracy (0 to 55°C)**

(Counts)

Resistance 100mΩ 1 to 650Ω 10 to 6250 100mΩ + Resistance 10mΩ 1 to 327Ω 100 to 32700 10Ω +

1.25Ω

0.65Ω

*Filter set for 10 Hz **Module only

The RTD/resistance module contains either a fixed terminal block (or a removable D-sub connector) providing connections for four 3-wire inputs for any combination of RTD and resistance input devices. Channels are wired as differential inputs. The illustration below shows the hardware features of the module.

1790D-4R0/T4R0 DeviceNet Module

Node Address Switches

Module and Network Status Indicators

Panel Mount Hole

DIN Rail Slot

DeviceNet Network Connection

CompactBlock LDX

1790D-8BV8V

8 INPUTS/8OUTPUTS-DC POWER

RTD/resistance Connections

RTD/resistance Channel Indicators

43223

(D-sub Connector shown)

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1-4 Overview

1790P-T4R0 PROFIBUS DP Module

DIN Rail Slot

PROFIBUS Network Connector

Module Power Connector (underneath module)

Node Address Switches

Module and Network Status Indicators

PROFIBUS Connector

Panel Mount Hole

RTD/resistance Channel Indicators

RTD/resistance Connections (Terminal block)

31341-M

System Overview

General Diagnostic Features

Module, network, and channel LEDs help you identify the source of problems that may occur during power-up or during normal channel operation. The LEDs indicate both status and power. See Chapter 4, Diagnostics and Troubleshooting, for details on power-up and channel diagnostics.

The modules communicate to the controller or network scanner via the DeviceNet™ or PROFIBUS network. The modules also receive 24V dc power through DeviceNet. An external 24V dc auxiliary source is required to power the RTD/resistance channels.

System Operation

At power-up, the module performs a check of its internal circuits, memory, and basic functions. If no faults are found during power-up diagnostics, the module status LED is turned on (green).

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Overview 1-5

Once a channel is properly configured and enabled, the module continuously converts the RTD or resistance input to a value within the range selected for that channel.

Each time the module reads an input channel, it tests the data for a fault (over- or under-range or open-circuit condition). If it detects a fault, the module sets a unique bit in the channel status word. See Input Data File on page 3-2. The module sends two’s compliment binary converted RTD/ resistance data out over the network. See Appendix B for a description of two’s compliment binary numbers.

Module Operation - DeviceNet Example

As shown in the block diagram below, each input channel of the module consists of an RTD/resistance connection that accepts excitation current; a sense connection that detects lead wire resistance; and a return connection. The signals are multiplexed to an A/D converter that reads the RTD or resistance value and the lead wire resistance.

Input

EXC0

SENSE0

RTN0

VA2

CH0

COM

Auxiliary 24Vdc Power

Multiplexer

VDC

GND

Channels 1 through 3 same as channel 0 above.

VA3

Analog Power Supply

VA1 VA1

EXC Current

AIN+1

A/D

AIN+2

A-GND

VA1 VA2 VA3

A-GND

AIN-

VREFVref

Channel Select

Optical Isolation

43224

Vcc

Micro Controller

GND

Vcc

GND

Transmit

Receive

Power Supply

Network

DeviceNet 24Vdc Power

From the readings taken by the converter, the module sends RTD or resistance data through the microcontroller to the DeviceNet network.

The PROFIBUS block diagram is similar.

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1-6 Overview

Chapter Summary

In this chapter, you learned about the 1790D/4R0/T4R0 and 1790P-TR40 RTD/resistance modules. See Chapter 2 to learn how to install and wire the modules.

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Installation and Wiring

Chapter

Before You Begin

Power Requirements

This chapter tells you how to:

• determine the power requirements for the modules

• avoid electrostatic damage

• install the module

• wire the module’s terminal block

1790D-4R0/T4R0

The module receives system power from the DeviceNet network. An auxiliary field supply provides power for the RTD/resistance channels.

Table 2.1 1790D-4R0/T4R0 Power Specifications

Power Specification

DeviceNet Supply voltage - 24V dc nominal

Voltage range - 11-28.8V dc Power dissipation - 1.2W maximum @ 28.8V dc

Field Supply voltage - 24V dc nominal

Voltage range - 21.6-26.4V dc (+ Power dissipation - 1.5W maximum @ 26.4V dc

10%)

1790P-T4R0

The module requires external supplies for both system power and for the RTD/resistance channels.

Table 2.2 1790P-T4R0 Power Specifications

Power Specification

PROFIBUS Supply voltage - 24V dc nominal

Voltage range - 19.2-28.8V dc Power dissipation - 2W maximum @ 28.8V dc

Field Supply voltage - 24V dc nominal

Voltage range - 21.6-26.4V dc (+ Power dissipation - 1.5W maximum @ 26.4V dc

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10%)

2-2 Installation and Wiring

General Considerations

The modules are suitable for use in a commercial or light industrial environment when installed in accordance with these instructions. Specifically, this equipment is intended for use in clean, dry environments

(1)

(Pollution degree 2

(2)

Category II

(IEC 60664-1).

) and to circuits not exceeding Over Voltage

(3)

Hazardous Location Considerations

This equipment is suitable for use in Class I, Division 2, Groups A, B, C, D or non-hazardous locations only. The following WARNING statement applies to use in hazardous locations.

WARNING

EXPLOSION HAZARD

• Substitution of components may impair suitability for

Class I, Division 2.

• Do not replace components or disconnect equipment

unless power has been switched off or the area is known to be non-hazardous.

• Do not connect or disconnect components unless

power has been switched off or the area is known to be non-hazardous.

• This product must be installed in an enclosure.

• All wiring must comply with N.E.C. article 501-4(b).

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(1)

Pollution Degree 2 is an environment where, normally, only non-conductive pollution occurs except that occasionally a temporary conductivity caused by condensation shall be expected.

(2)

Over Voltage Category II is the load level section of the electrical distribution system. At this level transient voltages are controlled and do not exceed the impulse voltage capability of the product’s insulation.

(3)

Pollution Degree 2 and Over Voltage Category II are International Electrotechnical Commission (IEC) designations.

Installation and Wiring 2-3

Environment and Enclosure

This equipment is intended for use in a Pollution Degree 2 industrial environment, in overvoltage Category II applications (as defined in IEC publication 60664-1), at altitudes up to 2000 meters without derating.

This equipment is considered Group 1, Class A industrial equipment according to IEC/CISPR Publication 11. Without appropriate precautions, there may be potential difficulties ensuring electromagnetic compatibility in other environments due to conducted as well as radiated disturbance.

ATTENTION

This equipment is supplied as "open type" equipment. It must be mounted within an enclosure that is suitably designed for those specific environmental conditions that will be present and appropriately designed to prevent personal injury resulting from accessibility to live parts. The interior of the enclosure must be accessible only by the use of a tool. Subsequent sections of this publication may contain additional information regarding specific enclosure type ratings that are required to comply with certain product safety certifications.

See NEMA Standards publication 250 and IEC publication 60529, as applicable, for explanations of the degrees of protection provided by different types of enclosure. Also, see the appropriate sections in this publication, as well as the Allen-Bradley publication 1770-4.1 ("Industrial Automation Wiring and Grounding Guidelines"), for additional installation requirements pertaining to this equipment.

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2-4 Installation and Wiring

ATTENTION

Preventing Electrostatic Discharge

This equipment is sensitive to electrostatic discharge, which can cause internal damage and affect normal operation. Follow these guidelines when you handle this equipment:

• Touch a grounded object to discharge potential static.

• Wear an approved grounding wriststrap.

• Do not touch connectors or pins on component

boards.

• Do not touch circuit components inside the equipment.

• If available, use a static-safe workstation.

• When not in use, store the equipment in appropriate

static-safe packaging.

WARNING

If you insert or remove the module while power is on, an electrical arc can occur. This could cause an explosion in hazardous location installations.

Be sure that power is removed or the area is nonhazardous before proceeding.

Selecting a Location

Reducing Noise

Most applications require installation in an industrial enclosure to reduce the effects of electrical interference. RTD inputs are highly susceptible to electrical noise. Electrical noise coupled to the RTD inputs will reduce the performance (accuracy) of the module.

Group your modules in the enclosure to minimize adverse effects from radiated electrical noise and heat. Consider the following conditions when selecting a location for the module. Position the module:

• away from sources of electrical noise such as hard-contact switches,

relays, and AC motor drives

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• away from modules which generate significant radiated heat.

In addition, route shielded, twisted-pair wiring away from any high voltage I/O wiring.

Installation and Wiring 2-5

Protecting the Circuit Board from Contamination

The printed circuit boards of analog modules must be protected from dirt, oil, moisture, and other airborne contaminants. To protect these boards, the system must be installed in an enclosure suitable for the environment. The interior of the enclosure should be kept clean and the enclosure door should be kept closed whenever possible.

Installing CompactBlock LDX I/O

Follow these steps to install the block:

1. Set the node address on the base block.

2. Mount the base block.

3. Wire the terminal blocks.

4. Connect the network cable.

These steps are explained in detail in the following procedures for both the 1790D-4R0/T4R0 DeviceNet and 1790P-T4R0 PROFIBUS DP modules.

Set the Node Address on the DeviceNet 1790D-4R0/T4R0 Base Block

Each base block comes with its internal program set for node address 63. To reset the node address, adjust the switches on the front of the block. The two switches are most significant digit (MSD) and least significant digit (LSD). The switches can be set between 00 and 63.

The rotary switches are read at block power up only. Switch settings between 64 and 99 cause the block to use the last valid node address stored internally.

Example: Node Address is set at 26

The node address may also be set through RSNetWorx for DeviceNet or a similar configuration tool. When software configuration is used for the node address, the switches must be set between 64 and 99.

43230

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2-6 Installation and Wiring

Set the Station Address on the 1790P-T4R0 PROFIBUS DP Base Block

To set the station address, adjust the switches on the front of the base block. The two switches are most significant digit (MSD) and least significant digit (LSD). The switches can be set between 00 and 99.

Mounting

The rotary switches are read at base block power up only

Example: Node Address is set at 26

43230

Mount the Base Block

You can mount the base block to a panel or DIN rail. We recommend that you ground the panel or DIN rail before mounting the block.

IMPORTANT

WARNING

The RTD and thermocouple base modules do not support any expansion blocks.

When used in a Class I, Division 2, hazardous location, this equipment must be mounted in a suitable enclosure with proper wiring method that complies with the governing electrical codes.

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Panel Mounting

1. Place the block against the panel where you want to mount it.

2. Gently pull and position the expansion cover to the left.

3. Place a center punch, nail or similar device through the mounting

holes in the block and make two marks on the panel (lower left and upper right corners of the module).

4. Remove the block and drill two holes in the panel to accommodate

each of the mounting screws.

Installation and Wiring 2-7

5. Replace the block on the panel and place a screw through each of the

two mounting holes. Tighten the screws until the block is firmly in

place

95 mm

3.74 in

CompactBlock LDX

41 mm

1.6 in

EXPANSION UNIT

1790-16BVOX

16 INPUTS-DCPOWER

Expansion Cover

43242

DIN Rail Mounting

1. Hook the top slot of the block over the DIN Rail.

2. Pull down on the locking lever while pressing the block against the

rail

Locking Lever

43243

3. Push up on the locking lever to secure the block to the rail when the

block is flush against the rail.

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2-8 Installation and Wiring

Connect the DeviceNet Cable to the 1790D-4R0/T4R0 Base Block

Follow these procedures when connecting the DeviceNet cable to the base block.

The required DeviceNet connector is not supplied with the block - you must purchase it separately. There are three types of connectors that you can order directly from Rockwell Automation or your local distributor:

• 1799-DNETCON - 5-position open style connector

• 1799-DNETSCON - 5-position open style connector with locking

screws

• 1799-DNC5MMS - 5-position open style to 5-pin micro male connector

with locking screws

WARNING

If you connect or disconnect the DeviceNet cable with power applied to this module or any device on the network, an electrical arc can occur. This could cause an explosion in hazardous location

installations.

Be sure that power is removed or the area is nonhazardous before proceeding.

Connect the DeviceNet wiring (drop line) to one of the DeviceNet connectors as shown below. A color-coded wiring diagram is also printed next to the connector on the left side of the module

CompactBlock LDX

Wiring Diagram for 1799-DNETCON

1790D-8BV8V

8 INPUTS/8OUTPUTS-DC POWER

V+ Red

Can_H White

Drain/Shield

Can_L Blue

V- Black

V+ Red

V- Black

Wiring Diagram for 1799-DNC5MMS

Drain/Shield

Can_H White

Can_L Blue

43245

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Installation and Wiring 2-9

Connect the PROFIBUS DP Terminal Connector to the 1790P-T4R0 Base Block

Follow these procedures to connect the PROFIBUS DP terminal connector to the base block.

WARNING

The required PROFIBUS female 9-pin D-sub connector is not supplied with the base block - you must purchase it separately.

Before you connect female 9-pin D-sub connector to the base block, make sure it is wired correctly as shown in the following table.

Pin Number: Name: Description:

1 shield Shield, Protective Ground

2 M24V Minus 24V Output Voltage

3 RxD/TxD-P Receive/Transmit-Data-P

4 CNTR-P Control-p

5 DGND Data Ground

If you connect or disconnect the PROFIBUS cable with power applied to this module or any device on the network, an electrical arc can occur. This could cause an explosion in hazardous location installations.

Be sure that power is removed or the area is nonhazardous before proceeding.

Table 2.3 Wiring Descriptions for 9-Pin D-Sub Connector

6 VP Voltage-Plus

7 P24V Plus 24V Output Voltage

8 RxD/TxD-N Receive/Transmit-Data-N

9 CNTR-N Control-N

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2-10 Installation and Wiring

Module Power Connector (underneath module)

Once you have properly wired the connector, attach it to the base block as shown below. Use the locking screws on the connector to fasten it to the base block.

PROFIBUS Connector

Green - GRD

Black - COM

Red - +24V dc

43249

Connect Power to the 1790P-T4R0 Block

To apply power to the block, refer to the above illustration.

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Installation and Wiring 2-11

Field Wiring Connections

System Wiring Guidelines

Consider the following when wiring your system:

General

• This product is intended to be mounted to a well-grounded mounting

surface such as a metal panel. Additional grounding connections from the module’s mounting tabs or DIN rail (if used) are not required unless the mounting surface cannot be grounded.

• Route field wiring away from any other wiring and as far as possible

from sources of electrical noise, such as motors, transformers, conductors, and ac devices. As a general rule, allow at least 15.2 cm (6 in.) of separation for every 120V of power.

• Routing field wiring in a grounded conduit can reduce electrical noise.

• If field wiring must cross ac or power cables, ensure that they cross at

right angles.

• To ensure optimum accuracy, limit overall cable impedance by

keeping your cable as short as possible. Locate the I/O system as close to your sensors or actuators as your application will permit.

• Tighten terminal screws with care. Excessive tightening can strip a

screw.

Shield Grounding

• Use Belden shielded, twisted-pair wire to ensure proper operation

and high immunity to electrical noise. Refer to the following table and the RTD Wiring Considerations below.

Table 2.4 Belden Shielded Wiring

Configuration

2-wire Belden™ 9501 or equivalent

3-wire less than 30.48 m (100ft.)

3-wire greater than 30.48 m (100 ft.) or high humidity conditions

(1) For additional information, see Table 2.5.

Recommended Cable

Belden 9533 or equivalent

Belden 83503 or equivalent

• Under normal conditions, the drain wire and shield junction should be

connected to earth ground, via a panel or DIN rail mounting screw at the module end.

• Keep shield connection to ground as short as possible.

• If noise persists for a device, try grounding the opposite end of the

cable. (You can only ground one end at a time.)

• Refer to Industrial Automation Wiring and Grounding Guidelines,

Allen-Bradley publication 1770-4.1, for additional information.

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Publication 1790-UM002A-EN-P

2-12 Installation and Wiring

RTD Wiring Considerations

Because the operating principle of the RTD module is based on the measurement of resistance, take special care when selecting your input cable. For 2-wire or 3-wire configurations, select a cable that has a consistent impedance throughout its entire length. Cable specifications are noted below.

Table 2.5 Cable Specifications

Description Belden #9501 Belden #9533 Belden #83503

When used? For 2-wire RTDs and

potentiometers

Conductors 2, #24 AWG tinned

copper (7 x 32)

Shield Beldfoil aluminum

polyester shield with copper drain wire

Insulation PVC S-R PVC Teflon

Jacket Chrome PVC Chrome PVC Red Teflon

Agency Approvals NEC Type CM NEC Type CM NEC Art-800, Type CMP

Temperature Rating 80°C 80°C 200°C

IMPORTANT

The RTD module requires three wires to compensate for lead resistance error. We recommend that you do not

For 3-wire RTDs and potentiometers. Short runs less than 100 feet and normal humidity levels.

3, #24 AWG tinned copper (7 x 32)

Beldfoil aluminum polyester shield with copper drain wire

For 3-wire RTDs and potentiometers. Long runs greater than 100 feet or high humidity levels.

3, #24 AWG tinned copper (7 x 32)

Beldfoil aluminum polyester shield with tinned drain wire

use 2-wire RTDs if long cable runs are required, as it reduces the accuracy of the system. However, if a two-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). The module’s terminal block accepts two AWG #14 gauge wires.

Publication 1790-UM002A-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.

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 .

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