Test #8

Question 0

Define sequential process

Answer 0

Sequential process consist of a sequence of one or more operations that must be performed in a defined order.

Question 1

Define discrete process

Answer 1

Consist of a series of distinct operations with a definite condition for initiating each operation.

Question 2

Define time-driven sequential process

Answer 2

Time-driven sequential processes move from one operation to the next due to a time interval expiring or an absolute time value being reached.

Question 3

Define event driven sequential process.

Answer 3

Event driven sequential processes move from one operation to the next due to an event.

Question 4

What does PLC stands for?

Answer 4

Programmable logic controller

Question 5

Name the five different types of PLC programming languages.

Answer 5

Ladder diagram, sequential function charts, functional block diagram, structured text, instruction list.

Question 6

State the four different sections of the PLC.

Answer 6

Central processing unit, input/output, communication, power supply.

Question 7

State the four functions of the input/output interface section.

Answer 7

Termination, signal conditioning, isolation, indication.

Question 8

Explain the termination function of the input/output section.

Answer 8

The field wiring from devices located on the machine or process attaches at the input/output modules.

Question 9

Explain the signal conditioning function of the input/output section.

Answer 9

Incoming or outgoing field values are:

1) Converted to the appropriate type;
2) Amplified to the appropriate levels;
3) Filtered;
4) Other signal conditioning depends on the device connected.

Question 10

Explain the isolation function of the input/output section.

Answer 10

Signals are both electrically and physically isolated via photo-optical sensors.

Question 11

Explain the indication section of the input/output section.

Answer 11

An indicator lamp or LED is driven by the inputn for diagnostics to indicate input or output bit status, or operational status of a device.

Question 12

Name the four modes of operation pf the SLC-500.

Answer 12

Run mode, program mode, single scan test mode, continuous scan test mode.

Question 13

Explain the run mode of operation.

Answer 13

The PLC executes the program in this mode.

Question 14

Explain the program mode of operation.

Answer 14

In this mode, the PLC can upload or accept a download of a program.

Question 15

Explain the single scan test mode of operation.

Answer 15

In this mode, the PLC executes the program once, but the output relays are not energized.

Question 16

Explain the continuous scan mode of operation.

Answer 16

In this mode, the PLC executes the program continuously, but the output relays are not energized.

Question 17

Currently, the PLC is operating in run mode and the laptop is offline. You have just finished writing a new program. Explain the steps you would take to have the PLC run your new program.

Answer 17

You need to connect the laptop to the PLC and then go online. Once online, you need to put the PLC into program mode and then download the program.

Question 18

Describe the XIC and XIO instructions and the result of each instruction when logic 0 then logic 1 is present at the indicated bit.

Answer 18

XIC is false when logic 0 is present and true when logic 1 is present.

XIO is true when logic 0 is present and false when logic 0 is present.

Question 19

What switches are XIC and XIO akin to?

Answer 19

XIC is akin to a NO switch, XIO is akin to a NC switch.

Question 20

What is the main difference between a TON and RTO instruction in terms of their operation?

Answer 20

The TON instruction has its accumulator reset when the rung goes false. The accumulator of the RTO is not reset when the rung goes false.

Question 21

What do the mnemonics EN, DN, and TT refer to with respect to a timer?

Answer 21

EN means enable.
DN means done.
TT means timer is timing.

Question 22

Explain how you would force bit 5 of the input file high as part of a troubleshooting procedure.

Answer 22

I would select bit 5 of the input file and install a force ON. Then I would enable the forces.

Question 23

You notice that the FORCED I/O LED is blinking. What should you do?

Answer 23

It indicates that forces are installed but not enabled. I would thus enable the forces.

Question 24

How is a subroutine SBR evaluated?

Answer 24

The instruction SBR is always evaluated as true.

Question 25

What is required for a rung to be evaluated as true?

Answer 25

A continuous path of true instructions.

Question 26

Explain the process involved when a PLC tries to execute a program.

Answer 26

The PLC scans the inputs and the output image file.
It then evaluates the ladder diagram from top to bottom, left to right.
It finally updates the outputs and sends them out to the plant.

Question 27

Why is it necessary to identify the processor in the software?

Answer 27

It is necessary to identify the processor so that the software can bring up the correct instruction set and input/output configuration.

Question 28

State 4 advantages of the laptop over the HHT when programming a PLC.

Answer 28

1) Creation of larger data files;
2) Creation of longer rungs;
3) Ladder logic programs to be documented;
4) Projects can be saved to disk;
5) Complete reports on the project can be printed.

Question 29

Name and describe the four groups of keys on the HHT.

Answer 29

Data entry keys, menu function keys, cursor keys, zoom and rung keys.

Question 30

Where are programs stored in the HHT?

Answer 30

Programs are stored in the memory.