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Information Tech QUIZ 1-Assessment
Questions with Answers
A piece of software called an assembler is used to convert Ladder Logic into machine code. - Correct answer T Siemens PLCs support set and reset, while Allen-Bradley PLCs support latch and unlatch. - Correct answer T A latching relay requires a branch instruction to hold the signal. - Correct answer F A seal-in circuit is a method for maintaining a signal after a momentary switch has been pressed and released. - Correct answer T Series logic could also be called OR logic - Correct answer F PLC systems usually require as much space in an enclosure as equivalent hardwired relay systems. - Correct answer F When the --| |-- instruction is associated with a physical input, the instruction will be set to 1 when there is no input voltage applied to the terminal. - Correct answer F A latch coil instruction is used with an unlatch coil instruction to control the state of an output. - Correct answer T Coils are output instructions. - Correct answer T Internal relays are known by a variety of names and it is important to be able to recognize them. - Correct answer T The programming device must be connected to the controller: - Correct answer both b and c (b) when entering a program c) when monitoring a program) An AND gate operates on the same principle as: - Correct answer a series circuit A NOR gate operates on the same principle as: - Correct answer an OR gate with an inverter connected to the output An OR gate operates on the same principle as: - Correct answer a parallel circuit
According to this block diagram of typical PLC architecture, block No. 6 represents the: - Correct answer power supply unit PLC proprietary architecture: - Correct answer all of the above (is the opposite to open architecture? makes it more difficult to connect devices made by other PLC manufacturers does not allow programs to be interchanged between different PLC manufacturers) If a PLC has a total scan time of 10 mos and has to monitor a signal that ______ then the controller may not detect this change. - Correct answer changes state twice in 5 mos According to this block diagram of typical PLC architecture, block No. 5 represents the: - Correct answer output module If you want to know when one or both matching bits in two different words are ON, you would use the logic instruction: - Correct answer OR Branch input instructions are used to create: - Correct answer parallel path of input instructions The output data is sent to the: - Correct answer output field devices The control plan stored in the PLC is called: - Correct answer a program In conventional logic circuits, binary 1 represents: - Correct answer all of these (the presence of a signal the occurrence of some event a high voltage level) The basic rule for an AND gate is: - Correct answer if all inputs are 1, the output will be 1 One-shot operation is a method to program an internal relay so that its contacts close for exactly one scan cycle. - Correct answer T Vertical contacts may be included in branching instructions to reduce the footprint of the program. - Correct answer F All inputs to a NAND gate must be 1 to produce a 1 output. - Correct answer F
Unlike personal computers, PLCs are: - Correct answer all of these (equipped with a control programming language equipped with input and output modules designed for the industrial environment) A ladder diagram is read ___________ and __________. - Correct answer left-to-right, top-to-bottom Which of the following is not a factor affecting the memory size needed for a particular PLC application? - Correct answer voltage rating of the field devices The status bit of switches and pushbuttons connected to a PLC are stored in the - Correct answer input image table file The addressing format used with PLCs: - Correct answer d) both b and c (b) indicates what PLC input is connected to what input device c) indicates what PLC output is connected to what output device) The memory organization of a PLC can be divided into two broad categories: - Correct answer program and data files The basic rule for an OR gate is: - Correct answer if one or more inputs are 1, the output will be 1 Electrical devices are shown in their normal (OFF, 0) condition. - Correct answer T The scan time is the time required for one complete execution of the user program. - Correct answer T When there is a true logic rung path, all parallel outputs in the rung become true - Correct answer T Parallel logic could also be called AND logic. - Correct answer F Ladder logic is a symbolic language. - Correct answer T Misunderstanding the way the PLC scans a program can cause programming bugs. - Correct answer T
For logical continuity, all paths on a rung must be true for the rung to be true. - Correct answer F Plug-in terminal compartments allow I/O modules to be easily connected and replaced on some PLCs. - Correct answer T The rung condition and the -- ( ) -- instruction are false if no logical continuity path has been established. - Correct answer T The number and type of inputs cannot be changed in a fixed PLC. - Correct answer T The symbol -| |- in a ladder logic diagram: - Correct answer can be thought of as a normally-open contact The actual scan time is: - Correct answer all of these (calculated and stored in the PLC's memory computed each time the END instruction is executed the time taken to scan inputs and outputs and execute the user program) _______________ I/So are typical of small PLCs that come into one package with no separate or removable units. - Correct answer fixed The central processing unit: - Correct answer looks at the inputs, makes decisions based on the program, and sets the outputs The last element to be entered on a ladder rung is a (n): - Correct answer coil Basically, the function of a PLC is to: - Correct answer makes logical decisions and control outputs based on them In the ladder diagram, power flow is from right to left. - Correct answer F Software can be installed and run on a personal computer which will allow the system designer to program a PLC. - Correct answer T All inputs to an AND gate must be 1 to produce a 1 output. - Correct answer T A PLC differs from a PC in that is it designed for use in electrical control applications. - Correct answer F nice - Correct answer nice If any input signal changes state very quickly, it is possible that the controller may never be able to detect the change. - Correct answer T
The PLC power supply module normally is rated to provide power for: - Correct answer the PLC backplane and I/O modules The basic rule for an XOR function is: - Correct answer if one or the other, but not both, inputs are 1, the output is 1 Which of the following is a factor in determining the total scan time? - Correct answer all of these (length of the ladder program type of instructions executed speed of the processor) Modifying relay-type process control circuits usually involves changing the: - Correct answer circuit wiring The response time of a system depends on a number of factors. Of these, the easiest to control is: - Correct answer scan time of the program A control-management PLC application normally requires a: - Correct answer large- size PLC Which of the following is not an advantage that PLCs offer over the conventional relay- type control system? - Correct answer higher current capacity Hardwired logic refers to logic control functions determined by the way devices are interconnected. - Correct answer T The status of the -- ( ) -- instruction is set to 1 to energize the output and to 0 to de- energize the output. - Correct answer T Each individual contact instruction can only be used once throughout the program. - Correct answer F Internal relays can have as many associated sets of contacts as needed. - Correct answer T The status of input and output devices is stored in a data table. - Correct answer T The greater the scan time, the faster the PLC can react to changes in inputs. - Correct answer F On some PLC models, branches can be established at both the input and output portions of the rung. - Correct answer T
When representing a circuit as a ladder diagram, the power rails are always represented next to each other as the terminals of a battery. - Correct answer F When dealing with PLC memory, one K of memory represents 1024 bits. - Correct answer T One of the most common PLC programming languages is ladder logic. - Correct answer T The programming device: - Correct answer all of the above (is used to enter the program into the memory of the processor is commonly a personal computer can be a hand-held device) Which of the following standard PLC programming languages is a graphical language? - Correct answer all of these (Function Block Diagram Ladder Diagram Sequential Function Chart) At the start of the PLC scan, the: - Correct answer status of all inputs are read Field devices or real-world devices refer to: - Correct answer all devices that are physically wired to the PLC A NOT function is used when a logic 1 must _______ some device. - Correct answer deactivate The __________ will account for most of the total memory of a given PLC system. - Correct answer user program The OR function, implemented using contacts, requires contacts connected in: - Correct answer parallel A gate is a device that: - Correct answer performs a logical decision based on its inputs The input/output system forms the interfaces through which field devices are connected to the controller. - Correct answer T Only one input to an OR gate must be 1 to produce a 1 output. - Correct answer T
Ladder logic is still the most common PLC programming language. - Correct answer T Removing the programming device from the PLC will not affect the operation of the user program. - Correct answer T All inputs to a NOR gate must be 1 to produce a 1 output. - Correct answer F Battery-backed relays are used to ensure that the states of the outputs and internal relays are not lost during a power outage. - Correct answer T A personal computer is seldom used as a PLC programming device. - Correct answer F Programmable control is based on logic functions that are programmable and easily changed. - Correct answer T Branching is not permitted for output instructions. - Correct answer F Energy flow (logical continuity) can only extend from left to right. Paths requiring any right-to-left flow will be neglected. - Correct answer T There is no difference between a relay schematic and a ladder logic program. - Correct answer F Contacts are output instructions. - Correct answer F The status bit of switches and pushbuttons connected to a PLC are stored in the: - Correct answer input image table file A NOR gate operates on the same principle as: - Correct answer an OR gate with an inverter connected to the output A (n) ______ scan pattern examines instructions rung by rung. - Correct answer horizontal The number of I/O points does not affect the memory size required for apple installation.
- Correct answer F A PLC power supply module does not typically supply power to the field devices. - Correct answer T Empty output terminals cannot be used to store internal relay states. - Correct answer F It takes the processor exactly the same amount of time to examine different types of instructions. - Correct answer F
In a PLC system, there is a physical connection between field input devices and field output devices. - Correct answer F The output latch coil and the output unlatch coil cannot have the same address. - Correct answer F Latching circuits and latching relays is the same thing. - Correct answer F The set and reset functionality available in some PLCs is similar to the latch and unlatch functionality available in others. - Correct answer T All PLC manufacturers organize their memories in the same way. - Correct answer F An internal relay does not directly control an output field device. - Correct answer T On some PLCs, only one output is allowed per ladder logic rung. - Correct answer T A latch coil instruction, when energized, sets and holds true the signal to an output field device until the output is reset using an unlatch coil instruction. - Correct answer T All gates are devices that have one input with which they perform logic decisions and produce a result at one or more of their outputs. - Correct answer F Scan time varies with program content and length. - Correct answer T A two-input OR function, expressed as a Boolean equation, would be Y=AB. - Correct answer F Most instructions require one word of memory. - Correct answer T Which module of the PLC is responsible for performing logical operations? - Correct answer processor According to the data stored in the word corresponding to the outputs, PL1 would be _____ and PL2 would be _________, respectively. - Correct answer off, on The _________ instruction always interprets a 1 status as true and a 0 status as false. - Correct answer --| |--
