PLC Midterm Test 1-5

Define the term producer/consumer I/O

A producer sends information in memory such as an input and consumer receives information in memory such as a controller for an input when it comes to outputs the controller is the producer and the output itself is the consumer.

Describe what a task contains in an Allen-Bradley Logix controller

A task contains programs, each with its own routines.

What is an I/O rack or chassis?

An I/O chassis is used for housing input and output modules

Describe when an interface occurs.

An interface occurs when two systems come together and communicate

List two terms that are used to describe an I/O device

Analog and discrete

List at least two I/O modules that require shielded cable to reduce the effects of electrical noise

Analog input and output modules.

The I/O section also converts varying voltage or current signals from analog input devices into corresponding decimal values by way of a(n)

Analog to digital converter.

What is the BCD system and why was it created?

BCD was created to convert large Decimal numbers into Binary for memory storage. BCD uses 4 binary digits to represent one decimal digit. BCD has a base of 2 because the digits are Binary. The largest Decimal number that can be displayed is 9.

PLCs are available with memory sizes ranging from as little as ____________________ for small systems up to 40MB (megabytes) for the larger systems.

4k

What is a PLC

A PLC is a solid state system originally designed to perform logic functions for the control and operation of manufacturing process equipment and machinery.

What is a Triac used for in an AC output module?

A Triac is used to isolate two different power sources from each other such as DC and AC. It is two SCR's connected in an inverse parallel connection that act as a switch.

Describe even parity.

Even parity is where the number of bits with a value of one are counted. If a number of bits is odd the parity bit is set to 1 to make the total number of 1s in a set an even number. If a number is even the parity bit is set to 0 to make the total number of 1's in a set an even number.

A task contains the actual ladder logic within a program

False

A typical PLC can be divided into three components consisting of the processor unit, the power supply, and the programming device.

False

Analog I/O devices are either ON or OFF, open or closed

False

I/O is updated asynchronous to the execution of the logic, which increases overall scan and I/O update times.

False

Status lights are provided for each output point to indicate when that point has been turned OFF

False

Storage memory is where the programmed ladder logic or program source code is storied

False

The ASCII code uses different combinations of 8 bit binary (base 2) information for communication of data.

False

The analog output module changes binary values generated in the PLC logic into analog signals using an RTD.

False

The binary system has a base 10

False

The key to the speed with which binary information can be processed is that there are only three states, each of which is distinctly different

False

How do you convert a negative binary number to the decimal equivalent?

First the negative Binary number is complemented, meaning that 1's are changed to 0 and 0's are changed to 1. Then you must add 1 to the complemented Binary number. You then use the negative Binary number to convert to a negative Decimal number using the place values. The place values are 1, 2, 4, and the signed bit has a place value of 8. You multiply the base values by the power of 10 to convert to Decimal. Once converted to decimal you add a negative sign.

How is ASCII information often expressed?

Hexadecimal

The ____________________ system is used when large numbers need to be processed.

Hexadecimal

____________________ registers typically store information generated and used by the processor when it is solving the user program.

Holding

What is the section of storage memory set aside for output status referred to?

I/O memory, output registers

Some older PLCs used the ____________________ numbering system for I/O addressing

Octal

For systems that operate on ____________________ parity, the parity bit is used to make the total of 1s add up to an odd number.

Odd

Describe the two states of binary signals

On and Off.

What is on-line programming?

Online programming is where the project is edited or modified after it has been downloaded to the PLC or in run mode.

The reluctance of the end user to learn a new language and the advent of the microprocessor gave the industry what is now known as the

PLC

An eighth bit is often used by programmers to provide error checking of information that is transmitted. This eighth bit is called the ____________________ bit.

Parity

The ____________________, or "brain," of the programmable logic controller is the decision-maker that controls the operation of the equipment to which it is connected.

Processor

The term ____________________ is used to distinguish actual devices that exist and must be physically wired from the internal functions of the PLC system that duplicate the function of relays, timers, counters, and so on, even though none physically exists.

Real World

____________________ is a high-level, real-world, graphic language that is understood by most electricians and technicians.

Relay ladder logic

When an output module is connected positive and provides current to the outside world (output device), the module is referred to as ____________________.

Sourcing

____________________ memory is that portion of memory that will store information on the status of input and output devices, preset and accumulated values of timers and counters, internal relay equivalents, numerical values for arithmetic functions, and so on.

Storage

Describe the hexadecimal system.

The Hexadecimal system is a numbering system with a base of 16. Numbers 0-9 are shown as that digit and numbers 10-15 are shown as letters A-F. The hexadecimal system is mainly used for processing large numbers. Its similar to other numbering systems just a different base with letters essentially.

Identify the parts of the processor.

The microprocessor, memory, communications circuitry, And input and output circuitry. The processor could have multiple processors as well such as a back plane processor and microprocessor.

While it is important that the PLC be installed or mounted in a central location, the use of remote I/O allows the input and output modules to be installed close to the actual operating equipment.

True

Words can be made up of 64-bits, 32-bits, 16-bits, or 8-bits

True

You should use DINT or REAL data types whenever possible as they use less memory and execute faster than other data types

True

Where is the programmed ladder logic stored?

User memory.

What are the three types of arrays

X, XY, XYZ or one dimensional, 2 dimensional, and 3 dimensional

With solid-state control systems, proper ____________________ helps eliminate the effects of electromagnetic induction.

grounding

A(n) ____________________ is used to program most of the PLCs on the market today

laptop

When a project is first developed and edited, it is normally done in the program or ____________________ mode.

off line

____________________ memory is where the status (ON or OFF) of all input and output devices are stored

storage

A binary number is always indicated by placing a 2 in subscript to the right of the unit's digit

true

The number of input and output modules necessary is dictated by the requirements of the equipment that is to be controlled by a PLC.

true

What are the two general classifications of processor memory?

user and storage

The ____________________ type output module is used when extra current ratings are required or when it is desirable to isolate loads of different voltages.

Contact output

List three things to consider before installing a PLC chassis or rack

Dust, vibration, and temp.

Describe electrical noise and how it is generated

Electrical noise is electrical interference created by certain devices and can interfere with the operation of the PLC's CPU. It is generated from devices with hard contacts

What is an EEPROM?

Electrically Erasable Programmable Read Only Memory

What determines the size, or power rating of a power supply?

The number and type of I/O modules that will be installed

What does the PLC power supply do?

The power source converts the available power to a low voltage DC power for the logic circuits of the processor and for the internal power required for the I/O modules.

Describe the job of the processor.

The processor interprets input signals and turns on or off outputs. The processor also interprets logic from a project

____________________ output modules are used for interfacing with discrete or integrated circuit (IC) TTL devices, LED displays, and various other 5 V DC devices.

Transistor-transistor Logic TTL

Discrete I/O modules are types of modules that only accept digital or ON- and OFF-type signals.

True

Even though the electromechanical relay has served well for many generations, the ever-increasing sophistication and complexity of modern processing equipment requires faster acting, more reliable control devices than electromechanical relays, timing and/or counting devices can offer.

True

Mathematically, each place value is expressed as a digit number times a power of the base, or 10, in the decimal numbering system.

True

Memory chips used in the processor can be separated into two distinct groups: volatile and nonvolatile

True

PLCs are designed to be operated by plant engineers and maintenance personnel with limited knowledge of computers.

True

The first step in converting 16-bit binary to hexadecimal is to group the 16-bit binary word into groups of four (conversion to BCD).

True

The input/output section, or I/O section, is the major reason that PLCs are so versatile when used with process machines or driven equipment.

True

The processor may be a self-contained unit, or may be modular in design, and plug directly into the I/O chassis.

True

The processor unit houses the microprocessor, memory module(s), and the communications circuitry necessary for the processor to operate and communicate with the I/O and other peripheral equipment.

True

The processor is often referred to as the ____________________.

brain

A(n) ____________________ is a group of eight bits.

byte

The ____________________ type of a tag defines the amount and function of bits and bytes (words) of memory assigned to the tag.

data

The ____________________ system uses ten unique numbers, or digits, which are 0 through 9

decimal

Any number that uses an exponent of 0, such as 10E0, has a place value of 10.

false 1

PLCs with ____________________ I/O typically come in a complete unit that contains the processor, I/O section, and power supply.

fixed