PLC final exam

A programmed XIC instruction:

with a bit status of 1 will have logic continuity.

The address I:1/3 identifies an input module residing in slot ___ of the PLC chassis.

one

The bit status condition of the input device shown connected to address I:2/8 must be ___ to turn on output address O:3/6.

0

For the input module shown, the data stored in the word corresponding to the open switch would be ___ and that for the closed switch would be ___ respectively.

1,0

For most PLC installations, a NEMA ____enclosure is recommended

12

Typically, PLC systems installed inside an enclosure can withstand a maximum of:

60 c inside the enclosure.

The address O:3/7 would be found on terminal ____ of an output module residing in slot ___ of the PLC chassis.

7,3

When using an XIC instruction, the reference address could be:

Any of these choices could be correct.

Parallel connections of ladder logic are typically called:

Branches

A ladder logic program consists of a number of rungs with each rung controlling an input.

False

All PLC manufacturers use the same method of I/O addressing.

False

Normally closed stop buttons are always entered as normally closed contacts on a PLC

False

PLCs will never scan in a left-to-right direction.

False

The method used by the CPU of a PLC to write a ladder logic program is called the scan

False

The PLC program shown is a ___ type.

Functional Block Diagram

The address for the point on the I/O module shown would be:

I:1/6

The most likely module address for LS1 is:

I:2/2

The memory organization of a PLC can be divided into two broad categories:

Program and data files

In Allen-Bradley controllers, ____ software is required to monitor, download, and upload programs.

RSLinx

In Allen-Bradley controllers, ____ software is required to develop and edit programs.

RSLogix

Each complete horizontal line of a ladder diagram is generally referred to as a(n):

Rung

With reference to the condition illustrated, what is the most likely fault?

Short circuit in the field device or wiring

Coils are output instructions.

True

Communications protocol is a standardized method for establishing communications between different PLC devices.

True

Hardwired MCRs are used to interrupt power to the I/O rack.

True

In Allen-Bradley controllers, RSLogix software is required to develop and edit ladder programs.

True

Internal relay coil is not accessible at the I/O rack.

True

PLCs are generally placed within an enclosure.

True

System commissioning should include checking for improper I/O addressing.

True

The procedure of pre-start-up inspection is commonly referred to as field checkout, or commissioning.

True

The term "nesting" is defined as a ladder logic condition when a branch within a branch exists.

True

The ____ instructions always interpret a 1 status as true and a 0 status as false.

XIC

The Boolean equation for the logic represented in the ladder diagram can be expressed as:

Y = (AB) + (ACD) + (DE)

A high voltage spike is generated whenever current to:

an inductive load is turned off.

A ladder rung is said to have logic continuity when:

at least one left-to-right true logical path exists.

PLCs are placed within an enclosure to provide protection against:

atmospheric conditions. conductive dust. moisture.

With reference to the input module circuit shown, a voltmeter reading of 24 VDC would indicate:

either a possible shorted PB or a possible fault in the field wiring.

The PLC will only accept multiple programs.

false

The majority of PLC system faults are caused by:

filed wiring and devices.

The first step in troubleshooting is to:

identify or describe the faulty operation.

The force instruction.

if used indiscriminately could cause haphazard machine operation.

Certain input field devices may have a small leakage current when they are:

in the off state

The addressing format used with PLCs:

indicates what PLC input is connected to what input device and indicates what PLC output is connected to what output device.

The Output Energize instruction:

is also known as the OTE instruction. signals the PLC to energize or deenergize the output. looks and operates like a relay coil.

Which of the following would not normally be located within the PLC enclosure?

limit switch

In addition to being an important safety measure, proper grounding of a PLC system can:

limit the effect of EMI

Editing a PLC program normally refers to:

making changes to an existing program.

Branch input instructions are used to create a:

parallel path of input instructions

Under no circumstances should:

signal wiring and power wiring be run in the same conduit.

Which of the following load devices is most likely to require some form of noise or voltage suppression?

solenoid

Malfunctions due to electrical noise interference usually cause:

temporary occurrence of operating errors.

Cross-talk interference can be caused by placing low voltage signal wiring and high voltage power wiring in the same conduit.

true

When routing power and I/O signal wiring to and within a PLC enclosure, you should:

use the shortest possible wire runs for I/O signals. never run signal and power wiring in the same conduit. run low-level signal conductors as shielded twisted pair.

The _________ will account for most of the total memory of a given PLC system.

user program

Which of the following is not normally included in the array of status indicators found on the processor module?

wiring ok

A programmed XIO instruction:

with a bit status of 1 will not have logic continuity nor is examined for an OFF condition.

A cable shield should be grounded at only one end

False

For the program shown, instruction A represents an:

Examine If Closed instruction.

For the program shown, instruction B represents an:

Examine If Open instruction.

The status bit of switches and pushbuttons connected to a PLC is stored in the:

Input image table file

The address for the point on the I/O module would be:

O:2/8

The most likely module address for PL1 is:

O:3/6

According to the data stored in the word corresponding to the outputs, PL1 would be ____, and PL2 would be ___ respectively.

OFF, ON

Which instruction is used to change the amount of logic scanned to progressively debug a program?

Temporary end

When the PLC is required to operate the user program without energizing any outputs, it is placed in the ___ mode.

Test

The highlighted instructions in the program rung shown indicate:

The instruction is true

A normally open limit switch is wired to an input module and programmed using XIO instruction. The instruction will be true when:

The limit switch is open.

The suppression circuit shown:

can be used to suppress DC loads. can be used to suppress AC loads. uses a metal oxide surge suppressor.

The last element to be entered on a ladder rung is a(n):

coil

In ladder logic programs, outputs are represented by:

coil symbols

Preparing a PLC control process for start-up is called:

commissioning.

With reference to the troubleshooting guide, which condition indicates no fault?

condition C

When a program rung consists of an output instruction only, the output would then be:

continuously ON