Category: A-B

What Is the 1746-QV Module?

The 1746-QV module is part of an SLC-based open-loop control

system for controlling the speed and placement of an hydraulic ram.

The module accepts an input from a linear displacement transducer

(LDT) and motion profiles that you program into the SLC processor,

and varies its output in the range of 10V dc. The SLC processor

sends to the module a pair of extend and retract profiles that define

when to accelerate or decelerate hydraulic motion.

What Is an SLC-500 System?

The Allen-Bradley Small Logic Controller (SLC) system is a

programmable control system with an SLC processor, I/O chassis

containing analog, digital, and/or special-purpose modules, and a

power supply. The 1746-QV module interfaces your hydraulic ram

and position-monitoring device (LDT) to the ladder sequence in your

SLC processor.

Minimizing Interference

from Radiated Electrical

Noise

Important: Signals in this type of control system are very susceptible to

radiated electrical noise. The module is designed to detect loss-of-sensor

and sensor noise conditions for any of the four axes when position values

are lost or corrupted. The Hydraulic Configurator displays these

conditions in the Status word window. The resulting hard or soft stop

depends on how you configured autostop conditions. (See Hydraulic

Configurator, Config word, and click on autostop “Help“).

To minimize interference from radiated electrical noise with correct

shielding and grounding:

• Connect LDT cable shields and drive output cable shields (all

shields at one end, only) to IFM terminal block SH terminals, and

connect the IFM terminal block GND terminal (51) to earth ground.

• Keep LDT signal cables far from motors or proportional amplifiers.

• Connect all of the following to earth ground:

– power supply cable shields (one end, only)

– LDT flange, frame, and machine

– I/O chassis

– AC ground

• Use shielded twisted pairs for all connections to inputs and outputs.

• Run shielded cables only in low-voltage conduit.

• Place the SLC-500 processor and I/O chassis in a suitable enclosure.

What Is the 1746-QS Module?

The 1746-QS Synchronized Axes Module provides four axes of

closed-loop synchronized servo positioning control, and lets you

change motion parameters while the axis is moving. The module has

four optically isolated inputs for signals from linear displacement

transducers (LDTs) and four optically isolated ±10 volt outputs that

interface with proportional or servo valve amplifiers.

The module’s microprocessor provides closed-loop control. The

module reads the axis position and updates the drive output every

two milliseconds, for precise positioning even at high speeds.

What Is the

Hydraulic Configurator

The module is designed for use with the Hydraulic Configurator, a

software product that you can obtain from the Allen-Bradley website on

the Internet. The Hydraulic Configurator is an interactive executable

that lets you configure the module and tune its axes. With it, you can:

• configure axes and store configuration parameters

• tune each axis independent of the ladder program

• store multiple commands to initiate repetitive axis motion

• display a log of the last 64 motion commands sent to the module

• observe and/or store plots of each axis

• access help screens that explain and/or describe module features

Important: The Hydraulic Configurator saves considerable time when

tuning axes and troubleshooting faults. Thereafter, your ladder logic

sequences module operation with the machine.

What Is an

SLC-500 System?

The Allen-Bradley Small Logic Controller (SLC) system is a programmable

control system with an SLC processor, I/O chassis containing

analog, digital, and/or special-purpose modules, and a power supply.

The 1746-QS module occupies one slot of the I/O chassis and

communicates with the SLC processor over the backplane using 32

words in the SLC processor’s output image table and 32 words in the

input image table. The processor loads or reads the module’s

configuration parameters using M0 or M1 files, respectively.

Overview

Install your power supply using these installation instructions. The only tools you

require are flat head (1/8”) and Phillips head (1/4”, #2) screwdrivers.

ATTENTION

!

Electrostatic discharge can damage integrated circuits or

semiconductors if you touch backplane connector pins. Follow

these guidelines when you handle the power supplies.

• Touch a grounded object to discharge static potential.

• Do not touch the backplane connector or connector pins.

• Do not touch circuit components inside the power supply.

• Use a static-safe work station, if available.

• Keep the power supplies in their static-shield packaging

when not in use.

Hazardous Location Considerations

Products marked CL1, DIV 2, GP A, B, C, D are suitable for use in Class I, Division

2, Groups A, B, C, D or nonhazardous locations only. Each product is supplied with

markings on the rating nameplate indicating the hazardous location temperature

code. When combining products within a system, the most adverse temperature

code (lowest T number) may be used to help determine the overall temperature

code of the system. Combinations of equipment in your system are subject to

investigation by the local authority having jurisdiction at the time of installation.

System Overview

The module communicates with the SLC 500 processor and receives

+5V dc and +24V dc power from the system power supply through

the parallel backplane interface. No external power supply is

required. You may install as many thermocouple modules in the

system as the power supply can support.

Each module channel can receive input signals from a thermocouple

or a mV analog input device. You configure each channel to accept

either one. When configured for thermocouple input types, the

module converts analog input voltages into cold-junction

compensated and linearized, digital temperature readings. The

module uses National Institute of Standards and Technology (NIST)

ITS-90 for thermocouple linearization.

When configured for millivolt analog inputs, the module converts

analog values directly into digital counts. The module assumes that

the mV input signal is linear.

System Operation

At power-up, the module checks its internal circuits, memory, and

basic functions. During this time the module status LED remains off. If

the module finds no faults, it turns on its module status LED.

General Description

This module mounts into 1746 I/O chassis for use with SLC 500 fixed

and modular systems. The module stores digitally converted

thermocouple/mV analog data in its image table for retrieval by all

fixed and modular SLC 500 processors. The module supports

connections from any combination of up to eight thermocouple/mV

analog sensors.

Input Ranges

The following tables define thermocouple types and associated

temperature ranges and the millivolt analog input signal ranges that

each of the module’s input channels support. To determine the

practical temperature range of your thermocouple, refer to the

specifications in Appendix A.

Each input channel is individually configured for a specific input

device, and provides open-circuit, over-range, and under-range

detection and indication.

Hardware Features

The module fits into any single slot for I/O modules in either an SLC

500 modular system or an SLC 500 fixed system expansion chassis

(1746-A2), except the zero slot which is reserved for the processor. It

is a Class 1 module using 8 input words and 8 output words.(2)

The module contains a removable terminal block providing

connections for eight thermocouple and/or analog input devices. On

the terminal block are two cold-junction compensation (CJC) sensors

that compensate for the cold junction at ambient temperature. It

should also be noted there are no output channels on the module.

Configure the module with software rather than with jumpers or

switches.

General Diagnostic Features

The thermocouple/mV module contains diagnostic features that can

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 7. Module Diagnostics

and Troubleshooting.

System Overview

The thermocouple 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 thermocouple modules in your system as the power supply can support.

Each individual channel on the thermocouple module can receive

input signals from thermocouple sensors or mV analog input devices.

You configure each channel to accept either input. When configured

for thermocouple input types, the thermocouple module converts the

analog input voltages into cold-junction compensated and linearized,

digital temperature readings. The 1746-NT4 uses the National Bureau

of Standards (NBS) Monograph 125 and 161 based on IPTS-68 for

thermocouple linearization.

When configured for millivolt analog inputs, the module converts the

analog values directly into digital values. The module assumes that the

mV input signal is already linear.

Hardware Features

The thermocouple module fits into any single-slot, except the

processor slot (0), in either an SLC 500 modular system or an SLC 500

fixed system expansion chassis (1746-A2). It is a Class 1 module (uses

8 input words and 8 output words). It interfaces to thermocouple

types J, K, T, E, R, S, B, and N, and supports direct ±50 mV and ±100

mV analog input signals.

The module requires the use of Block Transfer in a remote configuration.

The module contains a removable terminal block providing

connection for four thermocouple and/or analog input devices. There

are also two, cold-junction compensation (CJC) sensors used to

compensate for offset voltages introduced into the input signal as a

result of the cold-junction, i.e., where the thermocouple wires connect

to the module wiring terminal. There are no output channels on the

module. Module configuration is done via the user program. There are

no DIP switches.

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

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).

System Operation

The RTD module has 3 operational states:

· power-up

· module operation

· error (module error and channel error)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.