Allen-Bradley FLEX I/O 1794-IJ2 User manual

Brand: Allen-Bradley

Model: FLEX I/O 1794-IJ2

Type: User manual

User

Manual

FLEX I/O

Frequency

Input Module

(Cat. No. 1794-IJ2)

Allen-Bradley

Allen-Bradley Replacements

Important User Information 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 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

which 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

in part, without written permission of Allen-Bradley Company, Inc. is

prohibited.

Throughout this manual we make notes to alert you to possible injury to

people or damage to equipment under specific circumstances.

Attention helps you:

• identify a hazard

• avoid the hazard

• recognize the consequences

Important: Identifies information that is especially important for

successful application and understanding of the product.

Important: We recommend you frequently backup your application

programs on appropriate storage medium to avoid possible

data loss.

DeviceNet, DeviceNetManager, and RediSTATION are trademarks of Allen-Bradley Company, Inc.

PLC, PLC-2, PLC-3, and PLC-5 are registered trademarks of Allen-Bradley Company, Inc.

Windows is a trademark of Microsoft.

Microsoft is a registered trademark of Microsoft

IBM is a registered trademark of International Business Machines, Incorporated.

All other brand and product names are trademarks or registered trademarks of their respective companies.

ATTENTION: Identifies information about practices or

circumstances that can lead to personal injury or death,

property damage, or economic loss.

Publication 1794-6.5.11 - November 1997

Preface

Using This Manual

Purpose of this Manual This manual shows you how to use your FLEX I/O 2 input frequency

module with Allen-Bradley programmable controllers. The manual helps

you install, program and troubleshoot your module.

Audience You must be able to program and operate an Allen-Bradley programmable

controller to make efficient use of your FLEX I/O module. In particular,

you must know how to program block transfers.

We assume that you know how to do this in this manual. If you do not,

refer to the appropriate programming and operations manual before you

attempt to program your modules.

Vocabulary In this manual, we refer to:

– the frequency input module as the “input module”

– the Programmable Controller as the “controller”

Manual Organization This manual is divided into five chapters. The following chart lists each

chapter with its corresponding title and a brief overview of the topics

covered in that chapter.

Chapter Title Contents

1 Overview of FLEX I/O and Frequency

Input modules

Describes FLEX I/O frequency input modules, features,

and how they function

2 How to Install Your Frequency Input

Module

How to install and wire the module

3 Module Programming Explains block transfer programming, sample programs

4 Writing Configuration to and

Reading Status From with a Remote

I/O Adapter

Explains how to configure your modules and read status

information from your modules when using a remote I/O

adapter

5 How Communication Takes Place

and I/O Image Table Mapping with

the DeviceNet Adapter

Explains how you communicate with your modules, and

how the I/O image is mapped when using a DeviceNet

adapter

Appendix Title Contents

A Specifications Specifications for the frequency module

B Schematics Simplified schematics of frequency input module

Allen-Bradley Replacements

Publication 1794-6.5.11 - November 1997

-2 Using This Manual

Conventions We use these conventions in this manual:

For Additional Information For additional information on FLEX I/O systems and modules, refer to

the following documents:

In this manual, we show: Like this:

that there is more information about a topic

in another chapter in this manual

that there is more information about the

topic in another manual

Catalog

Number

Voltage Description

Publications

Installation

Instructions

User

Manual

1794

1794 FLEX I/O Product Data 1794-2.1

1794-ACN 24V dc ControlNet Adapter 1794-5.8

1794-ACNR 24V dc Redundant Media ControlNet Adapter 1794-5.18

1794-ACN15 24V dc ControlNet Adapter 1794-5.47

1794-ACNR15 24V dc Redundant Media ControlNet Adapter 1794-5.48

1794-ADN 24V dc DeviceNet Adapter 1794-5.14 1794-6.5.5

1794-ASB/C 24V dc Remote I/O Adapter 1794-5.50 1794-6.5.9

1794-ASB2/B 24V dc 2-Slot Remote I/O Adapter 1794-5.44 1794-6.5.13

1794-APB 24V dc Profibus Adapter 1794-5.40 1794-6.5.6

1794-IB8 24V dc 8 Sink Input Module 1794-5.30

1794-OB8 24V dc 8 Source Output Module 1794-5.31

1794-IB16 24V dc 16 Sink Input Module 1794-5.4

1794-OB16 24V dc 16 Source Output Module 1794-5.3

1794-IV16 24V dc 16 Source Input Module 1794-5.28

1794-OV16 24V dc 16 Sink Output Module 1794-5.29

1794-OB8EP 24V dc 8 Electronically Fused Output Module 1794-5.20

1794-IB8S 24V dc Sensor Input Module 1794-5.7

1794-IB10XOB6 24V dc 10 Input/6 Output Module 1794-5.24

1794-IE8 24V dc Selectable Analog 8 Input Module 1794-5.6

1794-6.5.21794-OE4 24V dc Selectable Analog 4 Output Module 1794-5.5

1794-IE4XOE2 24V dc 4 Input/2 Output Analog Module 1794-5.15

Table continued on next page

Publication 1794-6.5.11 - November 1997

Using This Manual -3

Summary This preface gave you information on how to use this manual efficiently.

The next chapter introduces you to the frequency module.

1794-OF4 24V dc 4 Output Isolated Analog Module 1794-5.37

1794-6.5.81794-IF4 24V dc 4 Input Isolated Analog Module 1794-5.38

1794-IF2XOF2 24V dc 2 Input/2 Output Isolated Analog Module 1794-5.39

1794-IR8 24V dc 8 RTD Input Analog Module 1794-5.22 1794-6.5.4

1794-IT8 24V dc 8 Thermocouple Input Module 1794-5.21 1794-6.5.7

1794-IRT8 24V dc 8 Thermocouple/RTD Input Module 1794-5.50 1794-6.5.12

1794-IJ2 24V dc 2 Frequency Input Module 1794-5.49 1794-6.5.11

1794-IA8 120V ac 8 Input Module 1794-5.9

1794-OA8 120V ac Output Module 1794-5.10

1794-TB2

1794-TB3

2-wire Terminal Base

3-wire Terminal Base

1794-5.2

1794-TBN Terminal Base Unit 1794-5.16

1794-TBNF Fused Terminal Base Unit 1794-5.17

1794-TB3T Temperature Terminal Base Unit 1794-5.41

1794-TB3S Spring Clamp Terminal Base Unit 1794-5.42

1794-TB3TS Spring Clamp Temperature Base Unit 1794-5.43

1794-TB3G Terminal Base Unit 1794-5.51

1794-TB3GS Spring Clamp Terminal Base Unit 1794-5.59

1794-CE1, -CE3 Extender Cables 1794-5.12

1794-NM1 Mounting Kit 1794-2.13

1794-PS1 24V dc Power Supply 1794-5.35

Catalog

Number

Voltage Description

Publications

Installation

Instructions

User

Manual

Allen-Bradley Replacements

Publication 1794-6.5.11 - November 1997

-4 Using This Manual

Table of Contents

Publication 1794-6.5.11 - November 1997

Overview of the Frequency

Input Module

Chapter 1

What This Chapter Contains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1

How You Use the Frequency Input Module . . . . . . . . . . . . . . . . . . . . . 1-1

What the Frequency Input Module Does. . . . . . . . . . . . . . . . . . . . . . . . 1-2

Typical Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3

Input Capabilities. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4

Selecting the Mode(s) of Operation. . . . . . . . . . . . . . . . . . . . . . . . . . 1-4

Output Capabilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5

Implementing Application Features . . . . . . . . . . . . . . . . . . . . . . . . .1-5

How Frequency is Calculated . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5

Frequency Calculation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5

Termination on Number of Pulses. . . . . . . . . . . . . . . . . . . . . . . . . . . 1-6

Missing Pulse Multiplier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-7

Direction Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-8

Chapter Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-9

How to Install Your Frequency

Input Module

Chapter 2

What This Chapter Contains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

Before You Install Your Input Module . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

European Union Directive Compliance. . . . . . . . . . . . . . . . . . . . . . . . . 2-1

EMC Directive. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

Low Voltage Directive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2

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

Wiring the Terminal Base Units (1794-TB3G shown) . . . . . . . . . . . 2-3

Installing the Module. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4

Mounting the Terminal Base Unit on a DIN Rail . . . . . . . . . . . . . . . 2-4

Panel/Wall Mounting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-6

Mounting the Frequency Input Module on the Terminal Base Unit . 2-7

Connecting Wiring for Your Frequency Input Module. . . . . . . . . . . . . 2-9

Connecting Wiring using a 1794-TB3G and –TB3GS

Terminal Base Units. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-10

Wiring connections for the 1794-IJ2 Frequency Input Module . . 2-11

Examples of Wiring to a 1794-TB3G Terminal Base Unit. . . . . . . 2-12

Module Indicators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-13

Chapter Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-13

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toc–ii Table of Contents – FLEX I/O Frequency Input Module

Publication 1794-6.5.11 - November 1997

Programming Your Frequency

Input Module

Chapter 3

What This Chapter Contains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

Enter Block Transfer Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

PLC-2 Family Processor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2

PLC-3 Family Processor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2

PLC-5 Family Processor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3

PLC-5/250 Processor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4

Chapter Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5

Writing Configuration to and

Reading Status from Your

Module with a Remote I/O

Adapter

Chapter 4

What This Chapter Contains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1

Configuring Your Frequency Input Module . . . . . . . . . . . . . . . . . . . . . 4-1

Reading Data From Your Module. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2

Mapping Data for the Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2

Frequency Input Module (1794-IJ2) Image Table Mapping . . . . . 4-2

Block Transfer Read Word Assignments for the Frequency

Input Module (1794-IJ2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3

Bit/Word Definitions for Block Transfer Read Words for the

Frequency Input Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3

Block Transfer Write Word Assignments for the Frequency

Input Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-5

Bit/Word Definitions for the Block Transfer Write Words for the

Frequency Input Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-6

Chapter Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-12

How Communication Takes

Place and I/O Image Table

Mapping with the DeviceNet

Adapter

Chapter 5

What This Chapter Contains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1

About DeviceNetManager Software . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1

Polled I/O Structure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1

Adapter Input Status Word . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-2

System Throughout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3

Mapping Data into the Image Table . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3

Frequency Input Analog Module (1794-IJ2) Image Table Mapping 5-3

Block Transfer Read Word Assignments for the Frequency

Input Module (1794-IJ2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-4

Block Transfer Write Word Assignments for the Frequency

Input Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-4

Bit/Word Descriptions for the Frequency Input Module

(1794-IJ2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-5

Defaults . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-13

Table of Contents – FLEX I/O Frequency Input Module toc–iii

Publication 1794-6.5.11 - November 1997

Troubleshoot the Frequency

Input Module

Chapter 6

What This Chapter Contains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-1

Status Indicators. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-1

Diagnostics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-3

Diagnostic Bits in Word 5 of the BTR File. . . . . . . . . . . . . . . . . . . . 6-3

What’s Next. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-3

Specifications Appendix A

What This Appendix Contains. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-1

Resolution and Accuracy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-4

Schematics Appendix B

What This Appendix Contains. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .B-1

Input Circuits. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .B-1

Frequency Inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .B-1

Gate Inputs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .B-1

Output Circuits. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .B-2

Digital Outputs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .B-2

DC to DC Converters (24V dc power supplies) . . . . . . . . . . . . . . . .B-3

Allen-Bradley Replacements

Publication 1794-6.5.11 - November 1997

Chapter

Overview of the Frequency

Input Module

What This Chapter

Contains

Read this chapter to familiarize yourself with the 1794-IJ2 module.

How You Use the

Frequency Input Module

The 1794-IJ2 module is an intelligent I/O module designed to perform

high-speed frequency algorithms. The module provides:

• 2 Frequency Inputs,

• 2 Gate Inputs and

• 2 Outputs.

The Frequency Inputs can accept frequencies up to 32,767 Hz. The

module accepts and returns binary data.

The module measures frequency over a user-specified time interval. A

frequency calculation can start before the time interval has elapsed, if a

user-specified number of frequency input pulses have occurred.

The module’s primary use is accurate, high-speed frequency

measurement. A high-speed internal clock is synchronized with the

frequency input to count over a user-selected sampling time or a

user-defined number of frequency input pulses.

All power for input devices (4 devices, 24 Vdc @ 15 mA max) is supplied

by the I/O module.

For information on See page

How You Use the Module . . . . . . . . . . . . . . . . . . . . . . . . 1-1

What the Frequency Input Module Does . . . . . . . . . . . . . 1-2

Typical Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3

Input Capabilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4

Selecting the Mode(s) of Operation. . . . . . . . . . . . . 1-4

Output Capabilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5

Implementing Application Features. . . . . . . . . . . . . 1-5

How Frequency is Calculated 1-5

Publication 1794-6.5.11 - November 1997

1-2 Overview of the Frequency Input Module

What the Frequency Input

Module Does

The frequency input module performs high-speed frequency and/or

scaling calculation operations for various industrial applications. The

module interfaces with a FLEX family adapter which then communicates

with a programmable controller

processor that has block-transfer

capability and external I/O devices.

The adapter/power supply transfers data to the module (block transfer

write) and from the module (block transfer read) using BTW and BTR

instructions in your ladder diagram program. These instructions let the

adapter read input values and status from the module, and let you write

output values and configure the module’s mode of operation. The

following illustration describes the communication process.

500/50mV

50mV

Select

24V IEC 1+

Magnetic

500/50mV

Magnetic

Gate Input

Frequency Input

CRISP

Bus Interface

Output 0

Output 1

Inter-Processor

Communication,

uP System 0/1

from

uP System 1

Data To/From Flexbus

Invert

Y/N

Invert

Y/N

Processing

Counter

Frequency / Count Data

uP System 0

Output Control

Input Control

Direction Data

IEC 1+/Contact

Input

VORTEX

Vortex

3Vin 6Vin 24V Power

IEC 1+/Contact

Input

50mV

Select

GND

Inputs

Module

Flexbus

24V Power

24VPower

Allen-Bradley Replacements

Publication 1794-6.5.11 - November 1997

Overview of the Frequency Input Module 1-3

Typical Applications You can use the 1794-IJ2 module in the power management, automotive,

food and beverage, and oil and gas industries for various flow and/or

turbine metering applications. Some sample applications include:

• turbine shaft speed monitoring

• automotive paint booths

• brewery flow monitoring

• petrochemical flow and custody transfer

ADAPTER

ACTIVE

FAULT

LOCAL

FAULT

24VDC

POWER SUPPLY

RIO ADAPTER

1794-ASB

Allen-Bradley

The adapter transfers your configuration data

to the module using a BTW.

Flexbus

External devices transmit

frequency signals to the module.

The module converts

frequency signals into integer

format and stores these values

until the adapter requests their

transfer.

Your ladder program instructs the

adapter to perform a BTR of the values

and stores them in a data table.

The adapter and module determine

that the transfer was made without error

and input values are within specified

range.

Your ladder program can use and/or move the data (if valid)

before it is written over by the transfer of new data in a

subsequent transfer.

Your ladder program performs BTWs to the module when you power

it up, and any time you wish to reconfigure the module.

FREQ

GATE

FREQUENCY INPUT 2 CHANNEL

1794-IJ2

Allen-Bradley

F0F

FREQ

GATE

OUT

Publication 1794-6.5.11 - November 1997

1-4 Overview of the Frequency Input Module

Input Capabilities The frequency module has 2 input channels (mode dependent). Each of

the 2 input channels may accept these input signals:

• magnetic pickup — 500mV to 28V ac peak (optional 50mV to

28V ac peak for increased signal sensitivity)

• proximity probe inputs

– compatible with Bently Nevada 3300 (5mm and 8mm) proximity

transducer systems

– provides 1 isolated 24V dc power supply (2 channels rated at

30mA each) to power external devices

– vortex flowmeter – 6V and 3V

You configure the module’s 2 input channels for your specific

application(s). Each input channel has two input selections:

Selecting the Mode(s) of Operation

You configure the 1794-IJ2 module for these modes of operation:

Channel 0

Channel 1

frequency input (F0)

gate input (G0)

frequency input (F1)

gate input (G1)

frequency input (F0-F1) - you connect

your input device to this input (ac, proximity

sensors switch, magnetic, vortex )

gate input (G0-G1) - you connect your

input device to this input (ac, proximity

sensors switch, magnetic, vortex )

used to determine direction - CW or CCW

2 input channels

FREQ

GATE

FREQUENCY INPUT 2 CHANNEL

1794-IJ2

Allen-Bradley

F0F

FREQ GATE

1F 1F

OUT

Mode Use this mode to:

Indicators/

Alarms

Scaler

values

Frequency and

% Full Scale

• monitor the frequency of an input with high accuracy (e.g. shaft)

• monitor the percent of full scale frequency

• operate frequency alarm (% full scale)

• scale the frequency

• monitor the direction of shaft rotation

• wire-off alarm with dc devices

• missing pulse alarm

√

Frequency and

Acceleration

• monitor the frequency of an input with high accuracy (e.g. shaft)

• monitor the acceleration (rate of speed change)

• operate acceleration alarm (rate of change)

• scale the frequency

• monitor the direction of shaft rotation

• wire-off alarm with dc devices

• missing pulse alarm

√

Allen-Bradley Replacements

Publication 1794-6.5.11 - November 1997

Overview of the Frequency Input Module 1-5

Output Capabilities The 1794-IJ2 module has 2 assignable outputs. These outputs are

designed for applications that require fast response. The outputs:

• are current sourcing at 10-31.2V dc (1A maximum per output)

• are electrically fused/current limited to 3A

• can be assigned to the associated input channel with user-selectable

frequency and acceleration values

• are isolated — this lets you use two separate external power supplies

if desired (one for output 0 and one for output 1)

Implementing Application Features

You can use the module to implement programmable application features

that are usually initiated by your PLC processor. This frees the PLC

processor to do other tasks and helps increase the overall throughput of

your PLC system.

How Frequency is

Calculated

The following paragraphs detail operation of the frequency input module

algorithm and its modifying parameters.

Frequency Calculation

Frequency is determined by a general algorithm which can be modified by

user defined parameters. In its simplest form, the algorithm employs the

user defined Minimum Sampling Time to set a window in which to count

pulses to determine the frequency. At least two pulses are required within

the sample window. Frequency is determined by storing the time the first

pulse occurred and then continually storing and updating the time of

subsequent pulses, along with the number of pulses encountered. When

the window expires, the frequency is calculated and the procedure repeats.

The sequence and formula for determining frequency are shown below.

This feature Is used in these modes To Alarm is ON when

frequency alarm frequency alarm selected

activate alarm when calculated or scaled

frequency is higher than user-specified

frequency value.

frequency > user-specified value

acceleration alarm

selected

activate acceleration alarm when acceleration is

greater than user-specified acceleration value.

acceleration >

user-specified value

scaling

% full scale and

acceleration

multiply and/or divide frequency by scalar

frequency > user-specified scaled

frequency value

Publication 1794-6.5.11 - November 1997

1-6 Overview of the Frequency Input Module

If only one pulse occurs within the sampling window, when the sample

time has expired, the window is extended to 2 seconds to allow for a

second pulse to occur. As soon as a second pulse occurs, the frequency is

calculated and the procedures starts over. If no second pulse is detected,

zero frequency is reported and a Missing Pulse Alarm is generated. The

following figure depicts this situation.

Termination on Number of Pulses

The normal mode is designed to provide wide bandwidth. However, it

requires the full 2 seconds to report a missing pulse. Another user

parameter, Number of Pulses to Terminate Sampling, is provided for

those situations where many pulses are expected within the sampling

window, such that early determination of frequency is possible.

ormal Mode Frequency Determination, at Least Two Pulses in Sampling Time

Frequency Reported

at End Sampling Time

T2 - T1

pulses counted - 1

Minimum Sampling Time

Frequency Input

Pulses

first pulse in window,

T1 time stored

pulses counted

last pulse in window

T2, update as each

pulse occurs

Missing Pulse Alarm Would be Reported

After 2 Seconds, If No Pulse Occurs

Normal Mode, Only One Pulse in Sampling Time, Sampling Time Extended

Frequency Reported at

First Pulse in Extended Time =

T2 - T1

2 - 1

Minimum Sampling Time

Frequency Input

Pulses

first pulse in window,

T1 time stored

2 = pulses counted

first pulse after window extended,

T2 time stored

Sampling Time Extended

to 2 Seconds

Missing Pulse Alarm Would be Reported After 2 Seconds, If No Pulse Occurs

Allen-Bradley Replacements

Publication 1794-6.5.11 - November 1997

Overview of the Frequency Input Module 1-7

During normal operation, there is a sufficient number of pulses to prevent

the module from entering the 2 second extension mode. Once the user

defined number of pulses is reached within the sampling window, the

frequency is immediately reported.

If the sampling window was extended to 2 seconds while waiting for a

second pulse to occur, a situation which can occur during system startup,

the module will not wait for the number of pulses to be reached. Instead,

as soon as a second pulse occurs, the frequency will be calculated based

on the time between the 2 pulses, and the procedure starts over.

Missing Pulse Multiplier

The last user parameter which is provided to modify the frequency

algorithm is the Missing Pulse Multiplier. In this case, the user can set the

number of Minimum Frequency Sampling Time windows they will allow

to extend the time to capture a second pulse, before reporting a Missing

Pulse Alarm. The intent with this parameter is to allow a tradeoff of the

bandwidth available with the response time to report a missing pulse. This

mechanism is shown in the following figure.

Termination on Number of Pulses

Frequency Reported at

Number of Pulses to Terminate Reached =

T2 - T1

Pulses to Terminate - 1

Minimum Sampling Time

Frequency Input

Pulses

first pulse in window,

T1 time stored

pulses to terminate

number of pulses to

terminate reached

T2, update as each

pulse occurs

Missing Pulse Alarm Would be Reported After 2 Seconds, If No Pulse Occurs

Publication 1794-6.5.11 - November 1997

1-8 Overview of the Frequency Input Module

Direction Detection

Direction detection is accomplished by using the Frequency input, Gate

input, and two sensors. The module expects to see a Low to High

transition on the Frequency input, followed by a Low to High transition

on the Gate input. This assumes both input polarity select bits are the

same selection.

This corresponds to Clockwise rotation (see figure). If a Low to High

transition occurs on the Gate input, followed by one on the Frequency

input, the rotation is CounterClockwise.

Missing Pulse Multiplier

Frequency Reported at

First Pulse in Extended Time =

T2 - T1

2 - 1

Minimum Sampling Time

Frequency Input

Pulses

first pulse in window,

T1 time stored

first pulse in an extended window,

T2 time stored

extended windows added one at time, until

pulse occurs or multiplied windows exceeded

Missing Pulse Alarm Would be Reported After Last Window, If No Pulse Occurs

possible extended window

2 = pulses counted

Sensor 0

Sensor 1

Clockwise Rotation

Frequency Input

IJ2 Module

Gate Input

2 x M

Sensor 0 (F)

Sensor 1 (G)

Clockwise

Rotation

Counter

Clockwise

Rotation

Sensor 0 (F)

Sensor 1 (G)

Direction Detection - Principle of Operation

Allen-Bradley Replacements

Publication 1794-6.5.11 - November 1997

Overview of the Frequency Input Module 1-9

Chapter Summary In this chapter, you learned about the frequency input module, block

transfer communication, and details of how the module functions. Now

you can install the module.

Install the

IJ2 Module

Publication 1794-6.5.11 - November 1997

1-10 Overview of the Frequency Input Module

Allen-Bradley Replacements

Publication 1794-6.5.11 - November 1997

Chapter

How to Install Your Frequency

Input Module

What This Chapter

Contains

In this chapter, we tell you about:

Before You Install Your

Input Module

Before installing your frequency input module in the FLEX I/O system:

European Union Directive

Compliance

If this product has the CE mark it is approved for installation within the

European Union and EEA regions. It has been designed and tested to

meet the following 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 50081-2EMC – Generic Emission Standard, Part 2 – Industrial

Environment

• EN 50082-2EMC – Generic Immunity Standard, Part 2 – Industrial

Environment

For information on See page

Before You Install Your Module . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

European Union Directives . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

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

Installing the Module. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4

on a DIN rail . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4

on a wall/panel. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-6

on the terminal base. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-7

Connecting Wiring. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-9

Module Indicators. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-13

You need to: As described under:

Calculate the power requirements of all modules in

each FLEX system.

Power Requirements, page 2-2

Position the keyswitch on the terminal base Installing the Module, page 2-4

ATTENTION: The frequency input module does not

receive power from the backplane. +24V dc power must be

applied to your module before installation. If power is not

applied, the module position will appear to the adapter as an

empty slot in your chassis.

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Allen-Bradley FLEX I/O 1794-IJ2 User manual

Allen-Bradley FLEX I/O 1794-IJ2 User manual

Allen-Bradley FLEX I/O 1794-IJ2 User manual

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