PLC Quiz #1

What is the standard programming language used with PLCs?

Ladder Logic.

What is the memory capacity, expressed in bits, for a PLC that uses 16-bit words and has an 8 K word capacity?

131,072 bits

What is a programmable automation controller (PAC)?

A device that uses both PLC and PC functions. Can be used for advanced control.

What is a programmable logic controller (PLC)?

An industrial grade computer that is capable of being programmed to perform control functions. It is basically a digital computer designed for use in machine control.

State two ways in which I/O is incorporated into the PLC.

Fixed and Modular.

List four criteria by which PLC's are categorized.

Functionality Number of inputs and outputs Cost Physical size

What are the two most common types of PLC programming devices?

Hand-held programming devices and PC's.

Explain the difference between open and proprietary PLC architecture.

Open architecture allows the use of parts from different manufacturers, while proprietary architecture uses most parts from the PLC manufacturer.

What two categories of software written and run on PCs are used in conjuncture with PLCs?

PLC programming and documenting software HMI (human machine interface), a monitoring system for alarms, readings, etc.

Explain the terms program and programming language as they apply to a PLC.

Program- A user-developed series of instructions that directs the PLC to execute actions. Programming Language- Provides rules for combining the instructions so that they produce desired actions.

List six distinct advantages that PLCs offer over conventional relay-based control systems.

Reliability, flexibility, lower cost, communication capability, faster response time, easier to trouble shoot.

Identify four tasks in addition to relay switching operations that PLCs are capable of performing.

Timing, counting, calculating, and the processing of analog signals.

Explain the main function of each of the following major components of a PLC: Processor module (CPU) I/O modules Programming device Power supply module

CPU; Controls all PLC activity, designed to be programmed with ladder logic. I/O Module; Forms the interface by which field devices are connected to the controller. Programming Device; Used to enter the desired program into the memory of the processor. Power Supply; typically uses DC power to feed the modules plugged into the rack.

Describe how the I/O modules connect to the processor in a modular-type PLC configuration.

Divided by compartments into which separate modules can be plugged.

The programmable controller operates in real time. What does this mean?

Input data is processed virtually immediately, firing its programmed output.

List five factors affecting the memory size needed for a particular PLC installation.

Number of I/O points used Size of control program Data-collecting requirements Supervisory functions required Future expansion

Compare the single-ended, multitask, and control management types of PLC applications.

Single-ended; Typically a stand alone application. one PLC controls one process. not associated with other PLC units on a site. Multitask; One PLC controlling Multiple processes. Adequate I/O capacity. Data communication applicable. Control Management; One PLC controls several other PLC's. requires a large processor to communicate. Must be capable of connection to all other associated PLC's.

What does the instruction set for a particular PLC refer to?

The different types of instructions used.